CC BY
30
ОРИГИНАЛНИ НАУЧНИ ЧЛАНЦИ ОРИГИНАЛЬНЫЕ НАУЧНЫЕ СТАТЬИ ORIGINAL SCIENTIFIC PAPERS
ACKNOWLEDGEMENT: The author is thankful for the financial support from the Ministry of Education and Science and Technological Development of the Republic of Serbia (National projects OI 174004, TR 34016).
LO Ol I
CP CP
<D £Z СЛ с <u
<u
STUDY OF THE APPLICATION OF PLASMA SPRAYED COATINGS ON THE SECTIONS OF THE ASTAZOU III B TURBO - JET ENGINE
о
m
Mihailo R. Mrdak g
Research and Development Center IMTEL Communications a.d., Belgrade -
e-mail: miki@insimtel.com, ORCID iD: ©http://orcid.org/0000-0003-3983-1605
DOI: 10.5937/vojtehg64-8933
FIELD: Chemical Technology ARTICLE TYPE: Original Scientific Paper t5
ARTICLE LANGUAGE: English
Summary:
The plasma spray process is used extensively in the aerospace industry for manufacturing key components exposed to excessively high temperatures, aggressive chemical environments, wear, abrasion, erosion and cavitation. The process covers a large field of parameters so that almost every layer can be combined with any other as well as with the base material. Coatings can be deposited uniformly; therefore, they allow worn components to be brought to final dimensions in the p process of aircraft repair. This research shows an effective procedure of the application of plasma spray coatings on the parts of the Astazou III B turbo - jet engine in the process of repair.The engine a. manufacturer,Turbomeca, has prescribed that powders should be f deposited by plasma spray systems under designation Metco 3M and 7M for the prescribed parameters of powder deposition, so that during the application of other plasma spray depositing systems the parameters must be tested and optimized. The aim was to apply the Plasmadyne plasma spray system during the repair process and to optimize the parameters, which will enable producing coatings that fulfill all the criteria prescribed in the engine manufacturer standard. The optimization of the parameters was carried out with a plasma gun MINI - GUN II with a large number of samples. This paper presents the optimal parameters of the deposition on the ASTAZOU III B engine casing, casing frame, duct and oil tank.The assessment of the coating
о
T3
<u
T3
mechanical properties was done by the HV03 microhardness testing method. Tensile bond strength of the coatings was investigated by a tensile test. The microstructures of the coating layers were evaluated on an optical microscope - OM. The analysis of the microstructures and the mechanical characteristics of the coatings was done in accordance with the TURBOMECA standard. The quality of the deposited coatings was confirmed by a 42-hour test of the ASTAZUO III B engine parts on a test stand. The performed tests have confirmed ER the quality of the coatings thus enabling the application of the plasma
CO
O >
o CM
ct spray technology in the process of the ASTAZOU III B engine
o o
o overhaul.
Key words: spray coatings, repairs, plasmas, engines, deposits, coating.
Introduction
<
o z
X
o
LU I—
>- The development of jet engines and the demands for increased
< resistance to oxidation, hot corrosion and sulphuring of engine parts influenced the development of the thermal spray process and nickelbased powders. For the protection of parts of jet engines, NiAl, NiCr, NiCrAl, NiCrAlY, CoCrAlY, NiCoCrAlY, etc. plasma spray coatings are ot commonly used today. The most effective protection of substrates from oxidation at temperatures above 800°C is provided by coatings which form oxides of the a-Al2O3 and Cr2O3 type. In most cases, coatings >o forming a continuous layer of a-Al2O3 are applied since this type of oxide
is superior and more reliable as compared to other types of oxides (Mrdak, 2012, pp. 182-201). At the beginning of the oxidation, NiO, a-§ Al2O3 and Cr2O3 oxide types are rapidly formed as well as spinel phases. o The relative ratio of these phases is determined by the initial composition of the alloy. As oxidation continues, the diffusion processes are beginning to show their effects. The nature of these effects depends on the content of the chemical elements in the coating and the diffusion parameters. When the coating has a low content of chromium and aluminum, protective continuous a-Al2O3 and Cr2O3 oxide layers cannot be formed on the coating surface; instead, undesirable continuous NiO oxide layers are formed. The mechanism of the NiO oxide growth causes the formation of micro pores in the oxide / alloy interlayer. Micro pores grow and merge into large macro pores. The mechanism of the NiO oxide growth creates significant stress which eventually leads to cracks in the oxide layer. The coefficient of the thermal expansion of NiO oxide and that of metal vary considerably. NiO oxide is subjected to tensile stresses as a metal base, so that the elastic deformation of the metal substrate causes breakage and peeling of the oxide layer on the coating surface (Mrdak, 2012, pp. 182-201). In order to build up continuous a-
Al2O3 and Cr2O3 oxide layers on the coating surface, a minimum of 20%Cr and 5%Al should be used for nickel alloys. NiCrAl alloy is added as well as yttrium for better cohesive oxide strength and better adhesive strength of the oxide coating on the substrate. Depending on the alloy type, the content of yttrium in the alloy ranges from 0.1 to 0.5% (Mrdak, 2012, pp.182-201). In exploitation, coatings are often exposed to the influence of impurities in the fuel and air. Depending on gas impurity, coatings can be exposed to a greater or lesser influence of Na, S and V. At high temperatures, diffusion processes occur at the interface between the coating and the gaseous environment, accelerating deposit corrosion. As far as air impurities are concerned, salt sucked by a turbojet engine is in the first place. Salt has the greatest impact on the corrosion of the parts of the turbojet engine that runs on distilled fuel without vanadium content. Salt sucked into the engine reacts with sulfur in the fuel to form sodium sulfate. In gas turbines that operate in the medium where chlorine is present, sodium chloride can also occur. This concerns air vehicles with a gas turbine developing a temperature at the turbine exit of about 750 °C, stationed on aircraft carriers or in coastal areas. Vanadium can also occur as impurity originating from fuel combustion. During fuel combustion, ash with a low melting point is created and deposited on the gas turbine components. Sulfur in fuel reacts with chromium from the alloy, thus forming chromium sulfate which precipitates on grain boundaries. During oxidation, chromium bonds with oxygen, simultaneously releasing sulfur that diffuses into the depth of the surface layer. In this way, new sulfides are formed beneath chromium oxide. Sulphur never goes into the atmosphere, but still diffuses through the surface layer, causing hot corrosion (Mrdak, 2012, pp.182-201). The experience of Turbomeca company which, in the production of the Astazou III B engine, applies plasma spray coatings resistant to oxidation and hot corrosion, as well as coatings for the repair of parts made of Al alloys, enabled the usage of plasma spray technology in the process of engine overhaul. The engine manufacturer prescribes that powder is to be deposited by plasma spray systems labeled Metco 3M and 7M for the prescribed parameters of powder deposition; therefore, the parameters must be optimized when applying other plasma spray depositing systems in order to meet all the criteria set by the Turbomeca standard. For saving and repairing engine parts from oxidation and hot corrosion, the manufacturer of the Astazou III B engine uses Ni/5Al, NiCr/6Al and Ni22Cr10Al1Y powders, and, for recovery of dimensions and repair of parts from aluminum alloys, it uses Al12Si powder. Composite Ni/5Al powder, due to its exothermic reaction during deposition, provides good bonding of the coating to the substrate. The products of this reaction are
co
"o >
CD
O CM
of
UJ
a.
Z)
o
o <
o
X
o
LU
H ^
a. <
H
<
CD >o
X LU H O
O >
intermetallic compounds NiAl3, Ni2Al3 and NiAl which add to the strength of the coating. These are thick coatings with metallurgical bond at the interface with the base material. The coating consists of lamellae of a solid solution of aluminum in nickel a-Ni (Al), and inter-lamellar oxides NiO and y-AI2O3 uniformly distributed over the boundaries of solid solution lamellae (Knotek, et al., 1980, pp.282-286), (Mrdak, 2015, pp.3255), (Mrdak, 2013, pp.7-22), (Svantesson, Wigren, 1992, pp.65-69). Coatings are resistant to oxidation, gas corrosion, wear, abrasion and erosion at temperatures up to 980°C. Bond strength with the substrate remains adequate to 700°C (Griffiths, et al., 1980). Coatings deposited in accordance with the Turbomeca standard have values of microhardness of min.140HV03 and bond tensile strength of min.35MPa. NiCrAl types of coatings in a deposited state consist of a solid solution of chromium and aluminum in nickel Y-Ni (Cr,Al). NiO, a-Al2O3, Cr2O3, and CrO3 oxide types are present in layers as well as Ni(Cr,Al2)O4 spinel phases (Badrour, et al., 1986, p.1217), (Brossard, et al., 2009, pp.1-9), (Mrdak, 2010, pp.5-16), (Mrdak, 2012, pp.182-201), (Mrdak, 2013, pp.7-22), (Tran, et al., 2008, p.701). Tensile bond strength of the coating stays adequate to the operating temperature of 980°C (Mrdak, 2012, pp.182201). Coatings deposited by the Turbomeca standard have values of microhardness of min.170HV03 and tensile bond strength of min.35MPa. NiCrAlY alloy is used to protect parts from hot corrosion and high temperature oxidation up to 1100°C (Material Product Data Sheet, 2013, Nickel Chromium Aluminum Yttrium (NiCrAlY) Thermal Spray Powders Amdry 963, DSMTS-0102.1, Sulzer Metco). Addition of yttrium is essential because it significantly increases the adhesion of Al2O3 and Cr2O3 oxides that are formed in the coating with the coating base, thus preventing cracking and separation of the protective surface oxide layer at thermal fatigue (Mrdak, 2012, pp.182-201). The structure of the inner layers of the coating consists of a solid solution of chromium and aluminum in nickel Y-Ni(Cr,Al) and the intermetallic compound Y'-Ni3Al. NiO, a-Al2O3, Cr2O3 and NiCr2O3 oxides are also present in the structure (Badrour, et al., 1986, p.1217), (Leea, 2005, pp.239-242). Coatings deposited by the Turbomeca standard have microhardness values of min. 200HV03 and tensile bond strength of min. 35 MPa. Al12Si coating is of a general purpose and is applied for the protection of new aviation parts and in the repair process to restore dimensions of aluminum and magnesium alloy parts changed due to wear (Material Product Data Sheet, 2011, Aluminum 12% Silicon Thermal Spray Powders Metco 52C-NS, DSMTS - 0045.2,Sulzer Metco), (Pramila Bai, Biswas, 1987, p.61). In the deposited state, the coating microstructure consists of two phases: a-Al solid solution and a-Al + Si eutectic mixture. Fine eutectic grains of
a-Al + Si are uniformly formed on the boundaries of the a-Al solid solution (Laha et al. 2005, pp. 5429-5438). Coatings deposited by the Turbomeca standard have microhardness values of min.70HV03 and tensile bond strength of min. 25 MPa. For all coatings, the allowed share of micro pores in the microstructure is max.8% and that of unfused particles is up to 15% of a particle size below 60^m (Turbojet enginestandard practices Manuel, Turbomeca).
The aim of the research was to apply the plasma spray system of the Plasmadyne company in repair of the Astazou III B engine and to optimize the powder deposition parameters, in order to produce coatings that will fulfill all the criteria prescribed in the standard of the engine manufacturer. The optimization of the parameters for a MINI - GUN II plasma gun was performed on fixed samples in a special tool. A large number of samples was made to obtain the microstructures and mechanical properties of coatings that will fulfill all the criteria prescribed by the Turbomeca standard. This paper presents the optimum parameters with which coatings are deposited on turbine casing, casing frame, duct and oil tank as well as the mechanical and structural characteristics of the coatings tested on the Astazou III B turbojet engine on the test stand. The performed tests have confirmed the quality of the coatings thus allowing the application of plasma spray technology in the Astazou III B engine overhaul.
Materials and experimental details
LO CM I
cp cp
<D £Z
eg c <u
<u
o
.Q
CO
O N CO
O <U tn
g
ro o o
T3
<u ro
For testing and applying coatings on the parts of the Astazou III B turbo-jet engine, four types of Sulzer Metco powders were used: Metco 450NS, Metco 443NS, Amdry 963 and Metco 52C-NS. Metco 450NS powder (Ni/5Al) based on Ni is intended to protect the turbine casing from the influence of high temperature, hot corrosion and erosion. The powder Ni/5Al particles coated with the Ni content of 95.5% and the Al content of 4.5% had a distribution of the granulate of 45-88 ^m (Metco 450NS Nickel/Aluminum Composite Powder, 2000, Technical Bulletin 10-136, Sulzer Metco). For the protection of the turbine casing frame ® from the impact of sand at lower temperatures, Metco 443NS powder (Ni19Cr/6Al) containing 19% Cr and 6% Al was applied. The powder had a grain range of 45-120 ^m (Metco 443NS Nickel- % Chromium/Aluminum Composite Powder, 2000, Technical Bulletin 10-130, 55 Sulzer Metco). To produce a coating resistant to high temperature oxidation and hot corrosion up to 1200 °C, applied to the duct, Ni22Cr10Al1Y powder alloy with a range of granulation of powder particles of 53-106 ^m was used (Material Product Data Sheet, 2013, Nickel Chromium Aluminum Yttrium (NiCrAlY) Thermal Spray Powders
co
"o >
CD
O CM
of
UJ
a.
Z)
o
o <
o
X
o
UJ
H ^
a. <
H
<
CD >o
X UJ
H O
O >
Amdry 963, DSMTS-0102.1, Sulzer Metco). To restore the size of the opening in the Astazou III B engine oil tank, Metco 52C-NS powder was applied, which is aluminum alloy with 12% Si. The granulation of the powder particles was from 45-90 ^m (Material Product Data Sheet, 2011, Aluminum 12% Silicon Thermal Spray Powders Metco 52C-NS, DSMTS - 0045.2,Sulzer Metco).
The investigation of the structural and mechanical characteristics of the coatings was done in accordance with the Turbomeca standard (Turbojet engine-standard practices manuel, TURBOMECA). The substrate material of the samples where Ni5Al, Ni19Cr6Al and Ni22Cr10Al1Y coating layers were deposited was stainless steel X15Cr13 (EN 1.4024) in the thermally unprocessed condition. The substrates of the samples where Al12Si coatings were deposited were made of AMS4117 aluminum alloy (AlMg1 EN5005). For microhardness testing and evaluation of the microstructure of the deposited state, 70x20x1.5 mm samples were made. The bases for examining tensile bond strength were 025x50mm. The investigation of the microhardness of coatings was done using the HV03 method. In order to assess the homogeneity of the coating layers, the microhardness measurement was carried out in a direction along the lamellae. Five readings of microhardness values were performed, in the middle and at the ends of the samples, out of which the two extreme values were rejected. The minimum and maximum values of the three remaining values are presented. Tensile bond strength was examined using the tensile test. The tests were performed at room temperature at a tensile speed of 10 mm / min on the hydraulic equipment. Every part of the Astazou III B engine was tested by five specimens. The engine parts samples were rotated at the same rotational speed to ensure the same conditions of coating deposition. The obtained results were averaged and the paper presents the average tensile bond strength values.
The microstructure of the deposited coating layers was examined on an optical microscope - OM. The analysis of the micro pores share in the coating was performed by treating 5 photos at 200X magnification. Through tracing paper, micro pores were labeled and shaded, with a total area of micropores calculated for the total surface of micrographs. The paper presents the mean values of the micropores share in the coatings. Table 1 shows the parts of the Astazou III B turbojet engine, the types of materials used for its parts and the operating conditions for the oparating parts on which coatings were deposited. All Astazou III B engine parts are made of special purpose aircraft materials. The oil tank is made of AG5 - EN AW-5083 aluminum alloy, the casing frame and the turbine casing of 15CDV6 - EN 1.7734 stainless steel, and the duct of AFNOR Z3NCT25 - ASTM A638 nickel alloy.
Table 1 - Parts of the ASTAZOU III B turbo-jet engine Таблица 1 - Детали турбореактивного двигателя ASTAZOU III B Tabela 1 - Delovi turbo-mlaznog motora ASTAZOU III B
No. Part name Material Operating conditions
1. Turbine casing 15CDV6 Temperature t=500-700°C erosion and hot corrosion
2. Casing frame 15CDV6 Air =200°C, sand particles
3. Duct Z3NCT25 High temperature tmax =1200°C, hot corrosion
4. Oil tank AG5 Synthetic oil t =80-120°C, wear
5 2
p p
<u
in gi
n e t e
o b
B
o z a t s
<
e
Turbomeca, engine manufacturer, prescribed that on the Astazou III B engine parts powders are to be deposited with Metco 3M and 7M equipment for the prescribed parameters of powder deposition and the standards on the quality of deposited coatings. Powder deposition parameters were optimised for an atmospheric plasma spray system of the Plasmadayne company that uses a specially designed plasma spray gun MINI - GUN II with the dimensions of 025 X 600 mm. A large number of samples were used and the paper shows the optimal parameters with which coatings were deposited on the Astazou III B turbojet engine parts tested on the test stand.
Powder was deposited on the samples and the parts under the same conditions in specially designed and manufactured tools. Coatings were deposited on the preheated rough samples and engine parts at a temperature of 90-120 °C. The MINI - GUN II plasma gun consisted of: anode A 2084-F45, cathode K 1083-129 and gas injector GI 2084 B - 103. The coating deposition was performed with the power supply of 40KW. All coatings were deposited with a plasma gas mixture of Ar-He. The layer thickness of NiAl, NiCrAl and NiCrAlY coatings with a single plasma gun pass was 25^m. The thickness of the Al12Si alloy layer with a single pass of the plasma gun was 30 um.
Figure 1 shows the APS - atmospheric plasma spray system of the Plasmadyne company used to produce coatings. The figure shows the process of powder deposition with a MINI GUN II plasma gun on the Astazou III B turbine engine in a cabin protecting from ionic radiation and noise. The deposition process is performed with a RISE robot.
c e s
s g
a o c d
e y
ar pr
s a m s
al lp
p p
a
y d
S
k a d
Figure 1 - Deposition of powder on the turbine casing of the ASTAZOU III B turbo-jet engine Рис. 1 - Нанесение порошка на корпус турбореактивного двигателя Нанесение
порошка на корпусе турбины в B турбореактивных Astazou III Slika 1 - Depozicija praha na kucistu turbine turbomlaznog motora ASTAZOU III B
Table 2 shows the plasma spray parameters for depositing powders with a MINI - GUN II plasma gun. The thickness of the deposited Ni5Al coating on the turbine casing and the Ni19Cr6Al coating on the casing frame was from 0.55 to 0.6 mm. The coating thickness was increased by 0.3 mm for extra machining. The Ni22Cr10Al1Y coating thickness on the edges of the duct ranged from 1.2 - 1.5 mm. It was increased by 0.3 mm for coating machining. At the opening of the oil tank, the Al12Si coating was deposited with a thickness from 0.54 to 0.6 mm with additional thickness for machining.
The investigation of the effect of the deposited coatings on the parts of the ASTAZUO III B turbojet engine was done at the test stand with the engine operation time of 42 hours. The wear of the coatings was determined on the basis of the change in the dimensions of machined surfaces after testing the engine parts. The change in dimensions was measured on a coordinate measuring machine MAUSER ML 28 at eight measuring points around the perimeter of cylindrical parts. This paper presents the mean values of coating wear in mm, compared with the values of allowed tolerances of machined parts.
Table 2 - Plasma spray parameters Таблица 2 - Параметры плазменнного напылителя Tabela 2 - Plazma sprej parametri
Parameters Ni5Al Ni19Cr6Al Ni22Cr10Al1Y Al12Si
Electric Current, (A) 800 800 750 800
Arc voltage, (V) 38 37 40 36
Primary plasma gas, Ar (l/min ) 75 75 50 75
Secondary plasma gas, He (l/min) 12 17 37 12
CD
Parameters Ni5Al Ni19Cr6Al Ni22Cr10Al1Y Al12Si
Carrier gas powder, Ar (l/min ) 7 12 10 7
Rotation of the disc for powder, (o/min ) 3.2 2.5 2.5 2.3
Distance of plasma guns, (mm) 60 60 65 60
Circumferential speed of the parts, ( mm/s ) 500 500 500 340
Plasma gun speed, (mm/s ) 3 3 3 3
Results and discussion
Figure 2 shows the turbine casing of the Astazou III B turbojet engine and the microstructure of the deposited Ni5Al coating. Red lines on the casing mark the inner surface protected by the plasma spray Ni5Al coating from hot corrosion and erosion caused by particles carried by gas. The microstructure of the Ni5Al coating is lamellar. The light blue lamellae of the coating consist of the a solid solution of aluminum in nickel a-Ni (Al). At the inter-lamellar boundaries of the a solid solution, there are evenly distributed nickel oxide NiO and aluminum y-AI203 marked with red arrows (Knotek, et al.,1980, pp.282-286), (Mrdak, 2013, pp.7-22), (Svantesson, Wigren, 1992, pp.65-69). Between the lamellae boundaries of the solid solution and oxide lamellae, there are irregularly shaped dark blue inter-lamellar pores. There are also spherical precipitates of a size of 18 to 25^m, which are always smaller than the granulation of deposited powders. The precipitates did not affect the mechanical properties of the coating. The layers of the deposited Ni5Al coating had the microhardness values of 155 - 179HV03. The mean value of the tensile bond strength of the coating was 72MPa. The mechanism of destruction was that of adhesion on the substrate / coating boundary. The values of the microhardness and tensile bond strength of Ni5Al coating are above the minimum values prescribed by the Turbomeca standard (min.140 HV03 and min.35 MPa) (Turbojet engine-standard practices manuel, TURBOMECA). The analysis of photomicrographs of Ni5Al coatings showed that the proportion of pores was 2.5%. The content of pores was significantly lower than the value set by the engine manufacturer Turbomeca (max.8°%pores). In the microstructure, there were no unfused powder particles of 45-60 ^m, whose presence is allowed in a content of up to 15% by the Turbomeca standard (Turbojet engine-standard practices manuel, TURBOMECA).
CI}
Figure 2 - Turbine casing of the ASTAZOU III B turbojet engine and the microstructure
of the Ni5Al coating Рис. 2- Корпус турбины турбореактивного двигателя ASTAZOU III B и микроструктура покрытия Ni5Al Slika 2 - Kuciste turbine turbomlaznog motora ASTAZOU III B i mikrostruktura prevlake
Ni5Al
Figure 3 shows the casing frame of the Astazou III B engine and the microstructure of the deposited Ni19Cr6Al coating. The inner surface of the casing frame marked with red lines has the deposited Ni19Cr6Al coating which protects the surface from abrasion of sand particles up to 200°C. Coating layers are deposited uniformly on the inner surface, with the coating mechanical properties and its microstructure showing the quality better than that prescribed by the Turbomeca standard. The values of microhardness and tensile bond strength in the Turbomeca standard are min.170HV03 and 35MPa (Turbojet engine - standard practices manuel, TURBOMECA).
<«Г)
Figure 3- Casing frame of the ASTAZOU III B turbojet engine and the microstructure of
the Ni19Cr6Al coating Рис. 3- Входная кромка корпуса турбореактивного двигателя ASTAZOU III B и
микроструктура покрытия Ni19Cr6Al Slika 3- Medukuciste turbomlaznog motora ASTAZOU III B i mikrostruktura prevlake
Ni19Cr6Al
The microhardness values of the coating were in the range of 278-315 HV03. The distribution of microhardness was directly related to the distribution of oxides and pores in the coating layers. The mean value of tensile bond strength of the coating was 52MPa. The character of destruction was adhesion. The structure of the coating layers is lamellar. The coating base consists of light blue lamellae of the solid solution of chromium and aluminum in nickel Y-Ni. At solid solution lamellae boundaries, there are the lamellae of oxides NiO, a-Al2O3, NiCr2O3 and a small amount of Cr2O3 marked with red arrows (Brossard, et al., 2009, pp.1-9), (Mrdak, 2012, pp.5-16), (Mrdak, 2012, pp.182-201). Between the boundaries of solid solution lamellae and oxide lamellae there are inter lamellar pores in dark blue. The analysis of photomicrographs showed that the Ni19Cr6Al coating layers had a share of micro pores of 3.5%. The analysis of the coating microstructure showed that the coating microstructure did not contain unfused powder particles whose presence is permitted by the Turbomeca standard in the amount up to 15% and of size under 60 ^m (Turbojet engine-standard practices manuel, TURBOMECA). Figure 4 shows the duct of the Astazou III B turbojet engine and the microstructure of the deposited Ni22Cr10Al1Y coating.
Ю
01 -
p p
<D
in gi
n e t e
o b
B
o z a
c e s
s g
a o c d e
;y
ar pr
s a m s
al lp
p p
a
;y d
S
k a d
CD
lo
>
О
2
ОС ш
ОС
U O
О
-J
A
О
NI
X
о ш
T
Y
ОС
A
S A
-J
О
KI
'У
NI
X ш
T O N
O
>
Figure 4 - Duct of the ASTAZOU III B turbojet engine and the microstructure of the Ni22Cr10Al1Y coating Рис. 4 - Промежуточный контур турбореактивного двигателя ASTAZOU III B и микроструктура покрытия Ni22Cr10Al1Y Slika 4 - Sprovodni aparat turbomlaznog motora ASTAZOU III B i mikrostruktura prevlake
Ni22Cr10Al1Y
The red lines mark the surfaces of the duct ridges where Ni22Cr10Al1Y coating layers were deposited, protecting the surface from high temperature oxidation and hot corrosion up to 1200°C. The microstructure of the deposited Ni22Cr10Al1Y coating is lamellar. The coating base consists of light blue lamellae of the y-Ní and Y'-Ni3Al solid solution. The internal structure of the coating is a heterogeneous mixture of the metal basis (y-Ní + Y'-Ni3Al) with precipitates, micropores and NiO, a-Al2O3, Cr2O3 and NiCr2O3 oxides (Badrour, et al., 1986, p.1217) (Leea, 2005, pp.239-242). At the interlamelar boundaries of the y-ní solid solution, there are oxides distributed, in darker shades of blue than the coating base. Dark blue, irregularly shaped pores are present between the boundaries of solid solution lamellae and oxide lamellae. Fine spherical precipitates of the size of 5 to 10^m are present in the
microstructure. The microhardness values of the deposited layers were in a range of 297 - 328HV03. The mean value of the coating tensile bond strength was 49MPa. The mechanism of destruction was adhesion on the substrate / coating boundary. The values of microhardness and tensile bond strength of the Ni22Cr10Al1Y coating are above the minimum value prescribed by the Turbomeca standard ( min.200 HV03 and Min.35 MPa) (Turbojet engine-standard practices manuel, TURBOMECA). The analysis of the micrographs of the Ni22Cr10Al1Y coating showed that the pore share was about 3%. The content of micro pores was lower than the value set by the engine manufacturer Turbomeca (max.8% pores). Unfused powder particles up to 60^im, whose presence is allowed in the content up to 15% by the Turbomeca standard (Turbojet engine-standard practices manuel, TURBOMECA), were not found in the microstructure. Figure 5 shows the oil tank of the Astazou III B turbojet engine and the microstructure of the deposited Al12Si coating. The hole in the oil tank is marked with a red circle, the inner surface of which is protected by the plasma sprayed Al12Si coating against the effects of synthetic oils and wear.
Figure 5 - Oil tank of the ASTAZOU III B turbojet engine and the microstructure of the
Al12Si coating
Рис. 5- Масляный резервуар турбореактивного двигателя ASTAZOU III B и микроструктура покрытия Al12Si Slika 5- Rezervoar za ulje turbomlaznog motora ASTAZOU III B i mikrostruktura
prevlake Al12Si
The microstructure of the Al12Si coating consists of two phases, the a-Al solid solution and the a-Al + Si eutectic mixture. At the boundaries of the a-Al solid solution, dendritic solidification resulted in a-Al + Si eutectic grains (Laha et al. 2005, pp. 5429-5438), (Pramila Bai, Biswas, 1987, p.61). The content of pores in the coating was negligible, which is why the coating microhardness value was at the upper limit of 130 HV03. The
mean value of tensile bond strength of 27MPa was in accordance with the coating microstructure. The mechanism of destruction was adhesion at the substrate / coating boundary. The values of microhardness and tensile bond strength of the Ni12Si coating are above the minimum value prescribed by the Turbomeca standard (min.70HV03 and min.25 MPa) (Turbojet engine-standard practices Manuel, Turbomeca). In the microstructure there are no unfused powder particles, although the Turbomeca standard allows their presence up to 15%, with a size below 60^m (Turbojet engine-standard practices Manuel, Turbomeca).
After the tests at the test station, the wear of the coatings was significantly lower than the allowable tolerance for engine parts. The Ni5Al coating wear on the turbine casing of 0.002 mm is significantly lower than the allowable tolerance of 0.3 mm. The Ni19Cr6Al coating wear on the casing frame was 0.0025 mm, while the allowed dimension tolerance for the casing frame is 0.3 mm. The Ni22Cr10Al1Y coating wear on the duct ridges was 0.001 mm, while the tolerance for the Ni22Cr10Al1Y coating on the duct ridges is 0.05 mm. At the opening of the oil tank, there were no changes in the size of the Al12Si coating, which is understandable because the coating is subjected to wear during opening and closing of the the tank when changing oil. The wear of the coatings on all tested parts was low. Based on the test results, plasma spray coatings have been successfully applied in the process of the general repair of the Astazou III B turbojet engine.
Conclusion
The research into the characteristics of coatings deposited on the Astazou III B turbojet engine parts by the atmospheric plasma spray system of the Plasmadyne company, with a MINI GUN II plasma gun, showed that they fully meet the criteria established by the engine manufacturer Turbomeca for coatings deposited by the Metco 3M and 7M plasma spray systems. The analysis of the structural and mechanical characteristics of the coatings in the laboratory and the testing of the components within the Astazou III B engine on the test station for a period of 42 hours showed that:
The deposited coating layers had good microhardness, tensile bond strength and microstructure values that meet the criteria prescribed by the Turbomeca standard. All coatings had the microhardness and tensile bond strength values above those prescribed by the Turbomeca standard. The microstructure of the deposited coatings does not show the presence of unfused powder particles up to 60 ^m, which is allowed by the Turbomeca standard up to 15%.
During coating testing on the engine parts at the test station, all coatings showed good adhesion and cohesive strength of layers. After dismantling the engine, delamination of coatings, coating peeling through layers and separation of layers from the surface of the engine parts were not found. On the surface of the coatings there are no networks of micro cracks. The coating surfaces on the casing, the casing frame and the oil tank opening showed no traces of burrs. On the duct ridges there are no traces from blade galling. °
The average value of wear of the Ni5Al coating on the turbine casing was 0.002 mm. On the casing frame, the average value of wear of the Ni19Cr6Al coating was 0.0025 mm. On the duct ridges, the average value of wear of the Ni22Cr10Al1Y coating was 0.001 mm. At the opening of the oil tank, there were no changes in the size of the Al12Si coating. For the Astazou III B engine parts, coating wear was much lower than the allowable tolerances for machining.
The wear of the coatings on all tested parts was low. Based on the test results, plasma spray coatings have been successfully applied in the process of the general repair of the Astazou III B turbojet engine.
of surface chemistry on splat formation for plasma sprayed NiCr onto stainless steel substrates, Surface&Coatings Technology SCT-15342, pp.1-9.
Griffiths , H., et al., 1980, 9th International Thermal Spray Conference. TheHague.
<D
m
Literature
Badrour, L., Moya, E. G., Bernardini, J., Moya, F., 1986, Scr. Metall. Vol.20, p.1217. Brossard, S., Munroe, P.R., Tran, A.T.T., Hyland, M.M., 2009, Study of the effects o
</> Cg
ro
c d
e y
ar
pr s
Knotek, O., Lugscheider, E. and Cremer, K.H., 1980, Alumina and Alurninide Formation in Nickel Aluminum Spraying Powders, pp.282-286, Proceedings of Ninth ^ International Thermal Spray Conference, Hague.
Laha, T., Agarwal, A., McKechnie, T., Rea, K., Seal, S., 2005, Synthesis of bulk nanostructured aluminum alloy component through vacuum plasma spray technique, Acta Materialia 53, pp.5429-5438.
Leea, D.B., 2005, High-temperature oxidation of NiCrAlY/(ZrO2-Y2O3) and ZrO2-CeO2-Y2O3) composite coatings, Center for Advanced Plasma Surface Technology, £ Sungkyunkwan University, Suwon 440-746, South Korea, Division of Materials Science and Engineering, Hanyang University, Seoul 133 -791, South Korea Available online 21 September 2004, Surface & Coatings Technology, Vol.193, pp.239-242.
Material Product Data Sheet, 2013, Nickel Chromium Aluminum Yttrium (NiCrAlY) Thermal Spray Powders Amdry 963, DSMTS-0102.1, Sulzer Metco. ft
Material Product Data Sheet, 2011, Aluminum 12% Silicon Thermal Spray Powders Metco 52C -NS,DSMTS - 0045.2, Sulzer Metco. ^
Metco 443NS Nickel-Chromium/Aluminum Composite Powder 2000, Sulzer -g Metco.Technical Bulletin 10-130.
Metco 450NS Nickel / Aluminum Composite Powder 2000, Sulzer Metco.Technical Bulletin 10-136.
CP
T3
со
"о >
CD
О ГМ
of
Ш
а.
Z)
о
о _|
< о
х о ш
н ^
а. <
н
(Л <
CD >о
X ш н о
О >
Mrdak, M., 2015, Investigation of the influence of plasma spray sealing coatings on the effect of sealing the TV2-117A turbojet engine compressor, Vojnotehnicki glasnik / MilitaryTechnical Courier, 63(1), pp.32-55.
Mrdak, M., 2013, Structure and properties of plasma sprayed APS - Ni20Al coatings, Vojnotehnicki glasnik/ Military Technical Courier, 61(2), pp.7-22.
Mrdak, M., 2012, Study of the properties of plasma deposited layers of nickel-chrome-aluminum-yttrium coatings resistant to oxidation and hot corrosion, Vojnotehnicki glasnik/ MilitaryTechnical Courier, 60(2), pp.182-201.
Mrdak, M., 2010, Uticaj brzine depozicije praha na mehanicke karakteristike i strukturu APS - NiCr/Al prevlake, Vojnotehnicki glasnik/MilitaryTechnical Courier, 58(4), pp.5-16.
Pramila Bai, B.N., Biswas, S.K., 1987, Wear 120, p.61.
Svantesson, J. and Wigren, J., 1992, A Study of Ni-5wt.Al Coatings Produced from Different Feedstock Powder, Journal of Thermal Spray Technology, Vol.1, No.1, pp.65-69.
Tran, A.T.T., Hyland, M.M., Qin, T., Withy, B., James, B.J., 2008, in: E. Lugscheider (Ed.), Thermal Spray 2008: Crossing Borders (Proceedings of International Thermal Spray Conference 2008). Pub. DVS - Verlag GmbH, 40223 Dusseledorf, Germany, p.701.
Turbojet engine-standard practices manuel, TURBOMECA.
ИССЛЕДОВАНИЕ ПО ПРИМЕНЕНИЮ ПЛАЗМЕННОГО НАПЫЛЕНИЯ ПОКРЫТИЯ ДЕТАЛЕЙ ТУРБОРЕАКТИВНОГО ДВИГАТЕЛЯ ASTAZOU III B
Михаило Р. Мрдак
Центр исследований и разработок АО „ИМТЕЛ Коммуникации", г.Белград, Республика Сербия
ОБЛАСТЬ: химические технологии
ВИД СТАТЬИ: оригинальная научная статья
ЯЗЫК СТАТЬИ: английский
Резюме:
Плазменное напыление широко применяется в области авиационной промышленности и производстве ключевых деталей, подверженных воздействию высоких температур, химически агрессивных средств, износу, повреждениям, эрозии и кавитации.
Процесс плазменного напыления включает широкое поле параметров, таким образом его возможно применять к каждому слою, в том числе и защитному слою покрытия. В процессе ремонта самолета плазменное покрытие наносится равномерно, тем самым выравнивая части поврежденных покрытий до необходимой толщины.
В данном исследовании представлен эффективный метод применения плазменного напыления покрытий частей турбореактивных двигателей ASTAZOU III B в процессе ремонта.
Производитель двигателей TURBOMECA рекомендует для покрытия своей продукции порошковые плазменные напылители системы Metco зМ или 7M, предписывая параметры нанесения покрытия, таким образом при применении иных плазменных напылитель-ных систем необходимо провести тестирования и испытания.
Цель данной работы состоит в разработке и производстве плазменного напылителя от компании Plasmadyne, которое будет соответствовать всем стандартам и удовлетворять требования производителя двигателей, с целью его применения в ремонте двигателей.
Проведена оптимизация параметров для плазменных пистолетов MINI - GUN II, в процессе которой было тестировано большое количество образцов. В работе представлены соответствующие параметры нанесения покрытия на корпус, входную кромку корпуса, промежуточный контур и масляный ре-зервоар турбореактивного двигателя ASTAZOU III B. Тестирование механических характеристик покрытия проводилось испытанием микротвердости покрытия, методом HV03.
Прочность соединения покрытия тестирована по методу испытаний на сдвиг при растяжении. Микроструктура слоев покрытия наблюдалась под оптическим микроскопом - OM. Анализ микроструктуры и механических характеристик покрытия был проведен в соответствии со стандартами и рекомендациями TURBOMECA.
Качество нанесенного покрытия подтверждено 42-х часовым испытанием частей двигателя ASTAZUO III B, проведенного в испытательной станции. Выполненные испытания подтвердили качество покрытия, таким образом доказано, что технологию плазменного напыление покрытий можно применять в процессе ремонта двигателей ASTAZOU III B.
Ключевые слова: плазменное покрытие; ремонт; плазменное напыление; двигатели; депозиты; покрытие.
STUDIJA PRIMENE PLAZMA NAPRSKANIH PREVLAKA NA SEKCIJAMA TURBOMLAZNOG MOTORA „ASTAZOU III B"
Mihailo R. Mrdak
Istrazivacki i razvojni centar IMTEL Komunikacije a.d., Beograd
OBLAST: hemijske tehnologije VRSTA CLANKA: originalni naucni clanak JEZIK CLANKA: engleski
Sazetak:
Plazma-sprej proces intenzivno koriste avio-industrije u proizvodnji kljucnih komponenti prekomerno izlozenih visokim temperaturama, he-mijski agresivnim sredinama, habanju, abraziji, eroziji i kavitaciji. Proces
>
pokriva veliko polje parametara, tako da se moze kombinovati skoro svaki sloj sa svakim i sa osnovnim materijalom. Prevlake mogu da se deponuju ravnomerno i stoga omogucavaju da se pohabane komponen-ö te dovedu na konacne dimenzije u procesu remonta vazduhoplova. U
ovom istrazivanju prikazan je efikasan postupak primene plazma-sprej prevlaka na delovima turbomlaznog motora ASTAZOU III B u procesu remonta. Proizvodac motora TURBOMECA predvideo je da se prahovi pe deponuju plazma-sprej sistemima sa oznakom Metco 3M ili 7M za koje
je propisao parametre depozicije prahova, tako da se kod primene dru-=5 gih plazma-sprej sistema parametri deponovanja moraju ispitati i optimi-
g zirati. Cilj rada bio je da se u remontu motora primeni plazma-sprej si-
_i stem firme Plasmadyne i izvrsi optimizacija parametara, koja ce omogu-
o citi da se proizvedu prevlake koje ce ispuniti sve kriterijume propisane
standardom proizvodaca motora. Izvrsena je optimizacija parametara za o plazma pistolj MINI - GUN II, pri cemu je uraden veliki broj uzoraka. U
w radu su prikazani optimalni parametri depozicije sa kojima su deponova-
> ne prevlake na kucistu, medukucistu, sprovodnom aparatu i rezervoaru
< za ulje motora ASTAZOU III B. Procena mehanickih karakteristika pre-
vlaka uradena je ispitivanjem mikrotvrdoce prevlaka metodom HV03. Za-tezne cvrstoce spoja prevlaka ispitane su metodom kidanja na zateza-nje. Mikrostrukture slojeva prevlaka procenjene su na optickom mikro-skopu - OM. Analiza mikrostruktura i mehanickih karakteristika prevlaka uradena je u skladu sa standardom TURBOMECA. Kvalitet deponova-nih prevlaka potvrden je 42-casovnim ispitivanjem delova u sklopu motora ASTAZUO III B na ispitnoj stanici. Izvrsena ispitivanja potvrdila su
o
o kvalitet prevlaka i na taj nacin omogucila primenu plazma-sprej tehnolo-
x
LU I— O
gije u proces remonta motora ASTAZOU III B. Uvod
g Razvoj turbomlaznih motora i zahtevi za povecanu otpotnost na
> oksidaciju, vrelu koroziju i sulfidizaciju delova motora uticali su na raz-
voj termo-sprej procesa i prahova na bazi nikla. Danas se za zastitu delova turbomlaznih motora najcesce primenjuju plazma-sprej prevlake NiAl, NiCr, NiCrAl, NiCrAlY, CoCrAlY, NiCoCrAlY i dr. Najefikasniju zastitu substratima od oksidacije na temperaturama iznad 800 °C pru-zaju prevlake koje formiraju okside tipa a-Al2Ü3 i Cr2O3. U vecini sluca-jeva, primenjuju se prevlake koje formiraju kontinualni sloj a-Al2O3, jer je ovaj tip oksida superiorniji i pouzdaniji u odnosu na druge tipove ok-sida (Mrdak, 2012, pp. 182-201). Kada je u prevlaci nizak sadrzaj hro-ma i aluminijuma, na povrsini prevlake ne mogu se formirati zastitni kontinualni slojevi oksida tipa a-Al2O3 i Cr2O3, vec se formiraju nepo-zeljni slojevi kontinualnih oksida NiO. Mehanizam rasta oksida NiO uzrokuje nastanak mikropora u medusloju oksid/legura. Mikropore ra-stu i spajaju se u velike makropore. Mehanizam rasta oksida NiO stva-ra velika naprezanja, koja na kraju postaju dovoljno velika da prave pr-skotine u oksidnom sloju. Da bi se nagradili kontinualni slojevi oksida a-Al2O3 i Cr2O3 na povrsini prevlake, za legure nikla potrebno je naj-
mnje 20%Cr i 5%Al. Legurama NiCrAl dodaje se i itrijum radi bolje ko-hezione cvrstoce oksida i adhezione cvrstoce prevlake sa supstratom. Zavisno od tipa legure, sadrzaj itrijuma se krece od 0,1 do 0,5% (Mr-dak, 2012, pp. 182-201). Iskustvo firme Turbomeka koja u proizvodnji motora ASTAZOU III B primenjuje plazma-sprej prevlake otporne na oksidaciju i vrelu koroziju, kao i prevlake za opravku delova od legure Al, omogucilo je da se pristupi primeni plazma-sprej tehnologije u po-stupku remonta motora. Proizvoúac motora predvideo je da se prahovi deponuju plazma-sprej sistemima sa oznakom Metco 3M ili 7M za koje je propisao parametre depozicije prahova, tako da se kod primene dru-gih plazma-sprej sistema parametri deponovanja moraju optimizirati, da bi prevlake ispunile sve kriterijume koje propisuje standard Turbo-meca. Za spasavanje i opravku delova motora od oksidacije i vrele ko-rozije proizvoúac motora ASTAZOU III B koristi prahove Ni/5Al, Ni-Cr/6Al i Ni22Cr10Al1Y, a za obnavljanje dimenzija i opravku delova od legure aluminijuma koristi prah Al12Si. Kompozitni prah Ni/5Al zbog egzotermne reakcije u procesu depozicije omogucava dobro vezivanje prevlake za supstrat. Produkti te reakcije su meúumetalna jedinjenja NiAl3, Ni2Al3 i Ni Al koja dodatno uvecavaju cvrstocu prevlake. To su guste prevlake sa metalurskom vezom na interfejsu sa osnovnim materi-jalom. Prevlaka se sastoji od lamela cvrstog rastvora aluminijuma u ni-klu a-Ni(Al) i meúulamelarnih oksida NiO i Y-Al2O3 ravnomerno raspo-reúenih po granicama lamela cvrstog rastvora (Knotek, et al.,1980, pp.282-286), (Mrdak, 2015, pp.32-25), (Mrdak, 2013, pp.7-22), (Svan-tesson, Wigren, 1992, pp. 65-69). Prevlake su otporne na oksidaciju, "5
CQ
O
gasnu koroziju, habanje, abraziju i eroziju na temperaturama do °
T3
980 °C. Cvrstoca spoja sa supstratom ostaje adekvatna do 700 °C (Grif- su fiths, H., et al., 1980). Deponovane prevlake po standardu Turbomeca 2 imaju vrednosti mikrotvrdoce min. 140HV03 i zatezne cvrstoce spoja min. 35MPa. Prevlake tipa NiCrAl u deponovanom stanju se sastoje od § cvrstog rastvora hroma i aluminijuma u niklu Y-Ni(Cr,Al). U slojevima Jg su prisutni oksidi tipa NiO, a-Al2O3, Cr2O3, CrO3 i spinel faze Ni(Cr,Al2)O4 (Badrour, et al., 1986, p.1217), (Brossard, et al., 2009, pp. 1-9), (Mrdak, 2010, pp. 5-16), (Mrdak, 2012, pp.182-201), (Mrdak, 2013, pp.7-22), (Tran, et al., 2008, p.701). Zatezna cvrstoca spoja prevlake ostaje adekvatna do radnih temperatura od 980 °C (Mrdak, 2012, pp. 182-201). Deponovane prevlake po standardu Turbomeca imaju ™ vrednosti mikrotvrdoce min. 170HV03 i zatezne cvrstoce spoja min. 35MPa. Legura NiCrAlY se koristi za zastitu delova od tople korozije i visokotemperaturne oksidacije do 1100 °C (Material Product Data Sheet, 2013, Nickel Chromium Aluminum Yttrium (NiCrAlY) Thermal Spray Powders Amdry 963, DSMTS-0102.1, Sulzer Metco). Dodatak itrijuma ima sustinski znacaj, jer bitno povecava adheziju oksida Al2O3 i Cr2O3
T3
koji se formiraju u prevlaci sa osnovom prevlake i tako sprecava puca- <o nje i odvajanje zastitnog povrsinskog oksidnog sloja pri dejstvu toplot- 13 nog zamora (Mrdak, 2012, pp.182-201). Struktura unutrasnjih slojeva prevlaka sastoji se od cvrstog rastvora hroma i aluminijuma u niklu
co
"o >
CD
O CM
D¿ UJ
a.
Z)
o
o <
o
X
o
LU
H >-
a. <
H
<
CD >Q
X LU H O
O >
Y-Ni(Cr,Al) i medumetalnog jedinjenja y'-N¡3AÍ. U strukturi su prisutni i oksidi NiO, a-Al2O3, Cr2O3 i NiCr2O3 (Badrour, et al., 1986, p.1217), (Leea, 2005, pp.239-242). Deponovane prevlake po standardu Turbo-meca imaju vrednosti mikrotvrdoce min. 200HV03 i zatezne cvrstoce spoja min. 35 MPa. Prevlaka Al12Si je opste namene i primenjuje se za zastitu novih vazduhoplovnih delova i u procesu remonta za obna-vljanje dimenzija delovima od legura aluminijuma i magnezijuma uzro-kovanih habanjem (Material Product Data Sheet, 2011, Aluminum 12% Silicon Thermal Spray Powders Metco 52C-NS, DSMTS - 0045.2,Sul-zer Metco), (Pramila Bai, Biswas, 1987, p.61). U deponovanom stanju mikrostruktura prevlake sastoji se od dve faze a-Al cvrstog rastvora i aAl + Si eutektikuma. Po granicama a-Al cvrstog rastvora ravnomerno se formiraju fina eutekticka zrna a-Al + Si (Laha, et al., 2005, pp.54295438). Deponovane prevlake po standardu Turbomeca imaju vrednosti mikrotvrdoce min. 70HV03 i zatezne cvrstoce spoja min. 25 MPa. Za sve prevlake, u mikrostrukturi dozvoljen je udeo mikropora maks. 8% i nestopljenih cestica do 15% velicine ispod 60pm (Turbojet enginestandard practices manuel, TURBOMECA).
Cilj rada bio je da se u remontu motora ASTAZOU III B primeni pla-zma- sprej sistem firme Plasmadyne i izvrsi optimizacija parametara de-pozicije praha, koja ce omoguciti da se proizvedu prevlake koje ce ispu-niti sve kriterijume propisane standardom proizvodaca motora. Izvrsena je optimizacija parametara za plazma pistolj MINI-GUN II na fiksnim uzorcima u posebnom alatu. Uraden je veliki broj uzoraka da bi se dobile mikrostrukture i mehanicke osobine prevlaka koje ce ispuniti sve kriterijume propisane standardom proizvodaca motora Turbomeca. U radu su prikazani optimalni parametri sa kojima su deponovane prevlake na ku-cistu turbine, medukucistu, sprovodnom aparatu i rezervoaru za ulje i mehanicko-strukturne karakteristike prevlaka, koje su ispitane u sklopu turbomlaznog motora ASTAZOU III B na ispitnoj stanici. Izvrsena ispiti-vanja potvrdila su kvalitet prevlaka i na taj nacin omogucila primenu pla-zma-sprej tehnologije u procesu remonta motora ASTAZOU III B.
Materijali i eksperimentalni detalji
Za ispitivanje i primenu prevlaka na delovima turbomlaznog motora ASTAZOU III B upotrebljena su cetiri tipa praha firme Sulzer Metco sa oznakama: Metco 450NS, Metco 443NS, Amdry 963 i Metco 52C-NS. Prah Metco 450NS (Ni/5Al) na bazi Ni namenjen je za zastitu kucista turbine od uticaja visoke temperature, tople korozije i erozije. Cestice oblo-zenog praha Ni/5Al sa sadrzajem 95,5% Ni i 4,5%Al imale su raspodelu granulata od 45 do 88 pm. Za zastitu medukucista turbine od uticaja pe-ska na nizim temperaturama primenjen je prah Metco 443NS(Ni19Cr/6Al) koji sadrzi 19%Cr i 6%Al. Prah je imao raspon gra-nulacije od 45 do 120 pm. Za izradu prevlake otporne na visokotempera-turnu oksidaciju i vrelu koroziju do 1200°C, koja se primenila na sprovodnom aparatu, koristio se prah legure Ni22Cr10AÍ1Y sa rasponom
granulacije cestica praha od 53 do 106 jm. Za obnavljanje dimenzija otvora na rezervoaru za ulje motora ASTAZOU III B primenjen je prah Metco 52C-NS, koji je legura aluminijuma sa 12%Si. Raspon granulacije cestica praha koji se koristio bio je od 45 od 90 jm. Ispitivanje struktur-nih i mehanickih karakteristika prevlaka raúeno je prema standardu TURBOMECA (Turbojet engine-standard practices manuel, TURBOME-CA). Materijal substrata uzoraka na kojem su deponovani slojevi prevlaka Ni5Al, Ni19Cr6Al i Ni22Cr10Al1Y bio je od nerúajuceg celika X15Cr13 (EN 1.4024) u termicki neobraúenom stanju. Osnove uzoraka na kojima su deponovane prevlake Al12Si napravljene su od legure aluminijuma AMS4117 (AlMg1 EN5005). Za ispitivanje mikrotvrdoce i za procenu mikrostrukture u deponovanom stanju napravljeni su uzorci dimenzija 70x20x1,5 mm. Osnove za ispitivanje zatezne cvrstoce spoja bili su dimenzija 025x50 mm. Ispitivanje mikrotvrdoce prevlaka raúeno je metodom HV0 3. Da bi se procenila homogenost slojeva prevlaka, mere-nje mikrotvrdoce izvrseno je u pravcu duz lamela. Obavljeno je pet ocita-vanja vrednosti mikrotvrdoce slojeva u sredini i na krajevima uzoraka, od kojih su odbacene dve krajnje vrednosti. Od tri preostale vrednosti prika-zane su minimalne i maksimalne vrednosti. Ispitivanje zatezne cvrstoce spoja raúeno je metodom ispitivanja na zatezanje. Testovi su raúeni na sobnoj temperaturi na hidraulicnoj opremi sa brzinom zatezanja od 10 mm/min. Uz svaki deo motora ASTAZOUIII B raúeno je po pet epruve-ta. Uzorci su sa delovima motora zajedno rotirani istom obimnom brzinom kako bi bili isti uslovi deponovanja prevlaka. Dobijeni rezultati su usrednjeni i u radu su prikazane srednje vrednosti zatezne cvrstoce spoja. Mikrostruktura slojeva deponovanih prevlaka ispitana je na optickom mikroskopu - OM. Analiza udela mikropora u prevlaci uraúena je obra-dom 5 fotografija na uvelicanju 200X. Preko paus-papira mikropore su oznacene i osencene, cija se ukupna povrsina racunala na ukupnu povr-sinu mikrofotografije. U radu su prikazane srednje vrednosti udela mikro-pora u prevlakama. Svi delovi motora ASTAZOU III B napravljeni su od namenskih vazduhoplovnih materijala. Rezervoar za ulje izraúen je od legure aluminijum AG5-EN AW-5083, meúukuciste i kuciste turbine od nerúajuceg celika 15CDV6-1.7734 EN, a sprovodni aparat od legure ni-kla AFNOR Z3NCT25 - ASTM A638. Proizvoúac motora TURBOMECA predvideo je da se na delovima motora ASTAZOU III B deponuju praho-vi sa opremom Metco 3M ili 7M za koje je propisao parametre depozicije prahova i standarde o prihvatljivosti kvaliteta deponovanih prevlaka. Za atmosferski plazma-sprej sistem firme Plasmadayne koji koristi specijal-no projektovani plazma-sprej pistolj MINI-GUN II dimenzija 025 X 600 mm, izvrsena je optimizacija parametara depozicije praha. Uraúen je veliki broj ispitnih uzoraka, a u radu su prikazani optimalni parametri sa ko-jima su deponovane prevlake na delovima koji su ispitani u sklopu turbo-mlaznog motora ASTAZOU III B na ispitnoj stanici. U posebno projekto-vanim i napravljenim alatima, pod istim uslovima uraúena je depozicija praha na uzorcima i delovima. Prevlake su deponovane na ohrapavljene i predgrejane uzorke i delove motora na temperaturi od 90 do 120°C.
C¿D
co
"o >
CD
O CM
D¿ UJ
a.
Z)
o
o <
o
X
o
LÜ
H >-
a. <
H
w <
CD ■O
X LÜ H O
O >
Plazma pistolj MINI- GUN II sastojao se od: anode A 2084 - F45, katode K 1083A - 129 i gas injektora GI 2084 B - 103. Depozicija svih pre-vlaka uradena je sa snagom napajanja od 40 KW. Sve prevlake su de-ponovane sa mesavinom plazma gasovima Ar-He. Debljine slojeva NiAl, NiCrAl i NiCrAlY prevlaka sa jednim prolazom plazma pistolja bila je 25 pm, a debljina sloja Al12Si legure sa jednim prolazom plazma pistolja 30 pm. Ispitivanje efekta deponovanih prevlaka na delovim turbomlaznog motora ASTAZUO III B radeno je na ispitnoj stanici sa vremenom rada motora od 42 casa. Pohabanost prevlaka odredena je na osnovu promene dimenzija masinski obradenih povrsina posle ispitivanja delova u sklopu motora. Merenje promena dimenzija radeno je na koordinatnoj mernoj masini MAUSER ML 28 na osam mernih mesta po obodu cilin-dricnih delova. U radu je prikazana srednja vrednost pohabanosti prevlaka, izrazena u mm, koja je uporedena sa vrednostima dozvoljenih tole-rancija masinski obradenih delova.
Rezultati i diskusija
Na kucistu je crvenim linijama oznacena unutrasnja povrsina koja je zasticena plazma-sprej prevlakom Ni5Al od tople korozije i erozije cestica koje gas nosi sa sobom. Mikrostruktura prevlake Ni5Al je lame-larna. Svetloplave lamele prevlake sastoje se od a cvrstog rastvora aluminijuma u niklu a-Ni(Al). Na medu-granicama lamela a cvrstog rastvora ravnomerno su distribuirani oksidi nikla NiO i aluminijuma y-Al2O3, oznaceni crvenim strelicama. Izmedu granica lamela cvrstog rastvora i oksidnih lamela prisutne su medulamelarne pore nepravilnog oblika tamnoplave boje. U mikrostrukturi su prisutni precipitati sfernog oblika, velicine od 18 do 25 pm, koji su uvek manji od granulacije pra-ha koji se deponuje. Prisutni precipitati nisu uticali na mehanicke ka-rakteristike prevlake. Slojevi deponovane prevlake Ni5Al imali su vred-nosti mikrotvrdoce od 155 do 179 HV0 3. Srednja vrednost zatezne cvr-stoce spoja prevlake bila je 72 MPa. Vrednosti mikrotvrdoce i zatezne cvrstoce spoja Ni5Al prevlake iznad su minimalnih vrednosti koje propi-suje standard TURBOMECA (min.140 HV03 i min. 35 MPa) (Turbojet engine-standard practices manuel, TURBOMECA). Analiza mikrofoto-grafija Ni5Al prevlake pokazala je da je udeo mikropora bio 2,5%. Sa-drzaj mikropora bio je znatno manji od vrednosti koje propisuje proiz-vodac motora TURBOMECA (max. 8% pora). U mikrostrukturi nisu uocene nestopljene cestice praha od 45 do 60 pm cije je prisustvo do-zvoljeno u sadrzaju do 15% po standardu TURBOMECA (Turbojet engine-standard practices manuel, TURBOMECA).
Na medukucistu je unutrasnja povrsina oznacena crvenim linijama na kojoj je deponovana prevlaka Ni19Cr6Al koja stiti povrsinu od abrazije cestica peska do 200°C. Slojevi prevlake deponovani su ravnomerno na unutrasnjoj povrsini sa mehanickim karakteristikama i mi-krostrukturom prevlake, koji po kvalitetu pokazuju bolje karakteristike od karakteristika propisanih standardom TURBOMECA. Vrednosti mi-krotvrdoce i zatezne cvrstoce spoja po standard TURBOMECA su min.
170HV03 i 35 MPa (Turbojet engine - standard practices manuel, TUR-BOMECA). Vrednosti mikrotvrdoce prevlake bile su raspona od 278 do 315 HV0 3. Raspodela mikrotvrdoce bila je u direktnoj vezi sa raspode-lom oksida i mikropora u slojevima prevlake. Srednja vrednost zatezne cvrstoce spoja prevlake bila je 52 MPa. Osnova prevlake sastoji se od svetloplavih lamela cvrstog rastvora hroma i aluminijuma u niklu Y-Ni. Po granicama lamela cvrstog rastvora prisutne su lamele oksida NiO, a-Al2O3, NiCr2O3, Cr2O3 i u manjoj kolicini CrO3, oznacene crvenim strelicama (Brossard, et al., 2009, pp. 1-9), (Mrdak, 2012, pp. 5-16), (Mrdak, 2012, pp.182-201). Izmedu granica lamela cvrstog rastvora i oksidnih lamela prisutne su i medulamelarne pore zagasito plave boje. Analiza mikrofotografija je pokazala da je u slojevima prevlake Ni19Cr6Al udeo mikropora bio 3,5%.
Crvenim linijama obelezene su povrsine venaca sprovodnog aparata na kojima su deponovani slojevi prevlake Ni22Cr10Al1Y, koji stite povrsine od visokotemperaturne oksidacije i vrele korozije do 1200°C. Mikrostruktura deponovane prevlake Ni22Cr10Al1Y je lamelarna. Osnova prevlake sastoji se od svetloplavih lamela cvrstog rastvora y-Ni i Y'-Ni3Al. Unutrasnja struktura prevlake je heterogena mesavina osnove metala (y-Ní + Y'-Ni3Al) sa precipitatima, mikroporama i oksidi-ma NiO, a- Al2O3, Cr2O3 i NiCr2O3 (Badrour, et al., 1986, p.1217) (Le-ea, 2005, pp.239-242). Vrednosti mikrotvrdoce deponovanih slojeva bile su u rasponu od 297 do 328HV03. Srednja vrednost zatezne cvrstoce spoja prevlake bila je 49 MPa. Vrednosti mikrotvrdoce i zatezne cvrstoce spoja prevlake Ni22Cr10Al1Y iznad su minimalnih vrednosti koje propisuje standard TURBOMECA (min. 200 HV0 3 i min. 35 MPa) (Turbojet engine-standard practices manuel, TURBOMECA).
Otvor na rezervoaru za ulje oznacen je crvenim krugom, cija je unutrasnja povrsina zasticena plazma-sprej prevlakom Al12Si od uticaja sintetickog ulja i habanja. Mikrostruktura Al12Si prevlake sastoji se od dve faze, a-Al cvrstog rasatvora i a-Al + Si eutektikuma. Po granicama a-Al cvrstog rastvora dendritskim ocvrscivanjem formirala su se eutektic-ka zrna a-Al + Si (Laha, et al., 2005, pp.5429-5438) (Pramila Bai, Biswas, 1987, p. 61). Sadrzaj mikropora u prevlaci bio je neznatan, zbog cega je prevlaka imala vrednost mikrotvrdoce na gornjoj granici od 130 HV0 3. Srednja vrednost zatezne cvrstoce spoja prevlake od 27MPa bila je u saglasnosti sa mikrostrukturom prevlake. Vrednosti mikrotvrdoce i zatezne cvrstoce spoja prevlake Ni12Si iznad su minimalnih vrednosti koje propisuje standard TURBOMECA (min. 70HV03 i min. 25 MPa) (Turbojet engine-standard practices manuel, TURBOMECA).
Pohabanost prevlaka posle ispitivanja delova na ispitnoj stanici bila je znatno manja u odnosu na dozvoljene tolerancije za delove motora. Pohabanost Ni5Al prevlake na kucistu turbine od 0,002 mm znatno je manja od vrednosti dozvoljene tolerancije od 0,3 mm. Pohabanost Ni19Cr6Al prevlake na medukucistu bila je 0,0025 mm. Dozvolje-na tolerancija dimenzija na medukucistu je 0,3 mm. Pohabanost
C2D
co
"o >
CD
O C\l
D¿ UJ
a.
Z)
o
o <
o
X
o
LÜ
H >-
a. <
H
w <
CD ■O
X LÜ H O
O >
Ni22Cr10Al1Y prevlake na vencima sprovodnog aparata bila je 0,001 mm. Tolerancija za prevlaku Ni22Cr10Al1Y na vencima sprovodnog aparata je 0,05 mm. Na otvoru rezervoara za ulje nije doslo do promena dimenzija prevlake Al12Si, sto je razumljivo, jer se prevlaka haba kod naizmenicnog otvaranja i zatvaranja rezervoara pri zameni ulja. Potrosnja prevlaka na svim delovima bila je mala. Na osnovu dobijenih rezultata ispitivanja, plazma-sprej prevlake su uspesno primenjene u postupku opste opravke turbomlaznog motora ASTAZOU III B.
Zakljucak
Istrazivanja karakteristika prevlaka deponovanih na delovima tur-bomlaznog motora ASTAZOU III B atmosferskim plazma-sprej siste-mom firme Plasmadyne, koji koristi plazma pistolj MINI-GUN II, poka-zala su da u potpunosti zadovoljavaju kriterijume koje je propisao pro-izvodac motora TURBOMECA za prevlake deponovane plazma-sprej sistemima Metco 3M i 7M. Analizom strukturnih i mehanickih karakteri-stika prevlaka u laboratorijskim uslovima i ispitivanjima delova u sklopu motora ASTAZOU III B na ispitnoj stanici u trajanju od 42 casa ustano-vljeno je da su slojevi prevlaka u deponovanom stanju imali dobre mi-krotvrdoce, zatezne cvrstoce spoja i mikrostrukture koje zadovoljavaju kriterijume propisane standardom TURBOMECA. Sve prevlake imale su vrednosti mikrotvrdoce i zatezne cvrstoce spoja iznad vrednosti koje propisuje standard TURBOMECA. U mikrostrukturi deponovanih prevlaka nisu prisutne nestopljene cestice praha do 60 pm, cije je prisu-stvo dozvoljeno u sadrzaju do 15% po standardu TURBOMECA.
U toku ispitivanja prevlaka u sklopu motora na ispitnoj stanici sve prevlake su imale dobru adhezionu i kohezionu cvrstocu slojeva. Posle rasklapanja motora na njegovim delovima nije uoceno raslojavanje prevlaka, ljustenje prevlaka kroz slojeve i odvajanje slojeva prevlaka sa povrsina delova. Na povrsinama prevlaka nisu prisutne mreze mikropr-skotina. Povrsine prevlaka na kucistu, medukucistu i otvoru rezervoara za ulje bile su bez tragova riseva. Na vencima sprovodnog aparata nisu prisutni tragovi i brazde od struganja lopatica.
Prosecna vrednost pohabanosti prevlake Ni5Al na kucistu turbine bila je 0,002 mm. Na medukucistu prosecna vrednost pohabanosti prevlake Ni19Cr6Al bila je 0,0025 mm. Na vencima sprovodnog aparata prosecna vrednost pohabanosti prevlake Ni22Cr10Al1Y bila je 0,001 mm. Na otvoru rezervoara za ulje nije doslo do promena dimenzija prevlake Al12Si. Na delovima motora ASTAZOU III B pohabanost prevlaka bila je mnogo manja od dozvoljenih tolerancija za masinsku obradu delova.
Potrosnja prevlaka na svim delovima bila je mala. Na osnovu dobijenih rezultata ispitivanja, plazma-sprej prevlake uspesno su prime-njene u postupku opste opravke turbomlaznog motora ASTAZOU III B.
Kljucne reci: sprej prevlaka, popravka, plazma, motori, depoziti, prevlaka.
Datum prijema clanka / Дата получения работы / Paper received on: 29. 08. 2015. Datum dostavljanja ispravki rukopisa / Дата получения исправленной версии работы / Manuscript corrections submitted on: 21. 10. 2015.
Datum konacnog prihvatanja clanka za objavljivanje / Дата окончательного согласования работы / Paper accepted for publishing on: 23. 10. 2015.
© 2016 Autor. Objavio Vojnotehnicki glasnik / Military Technical Courier (www.vtg.mod.gov.rs, втг.мо.упр.срб). Ovo je clanak otvorenog pristupa i distribuira se u skladu sa Creative Commons licencom (http://creativecommons.org/licenses/by/3.0/rs/).
© 2016 Автор. Опубликовано в "Военно-технический вестник / Vojnotehnicki glasnik / Military Technical Courier" (www.vtg.mod.gov.rs, втг.мо.упр.срб). Данная статья в открытом доступе и распространяется в соответствии с лицензией "Creative Commons" (http://creativecommons.org/licenses/by/3.0/rs/).
© 2016 The Author. Published by Vojnotehnicki glasnik / Military Technical Courier (www.vtg.mod.gov.rs, втг.мо.упр.срб). This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/rs/).
C2D
