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MECHANICAL PROPERTIES AND THE MICROSTRUCTURE OF THE PLASMA-SPRAYED ZrO2Y2O3 / ZrO2Y2O3CoNiCrAlY/ CoNiCrAlY COATING
Mihailo R. Mrdak
Research and Development Center IMTEL Communications a.d.,
Belgrade, Republic of Serbia,
e-mail: [email protected],
ORCID iD: http://orcid.org/0000-0003-3983-1605
DOI: 10.5937/vojtehg65-10586
FIELD: Chemical Technology ARTICLE TYPE: Original Scientific Paper ARTICLE LANGUAGE: English
Summary:
ZrO2 stabilized with Y2O3 has superior and excellent physical properties compared to other modern ceramic materials. Due to its high biocompatibility, ZrO2 ceramics in the ZrO2 - Y2O3 system is widely used as a biomaterial in orthopedic surgery. ZrO2 - Y2O3 ceramics is widely applied in the production of the head of the hip, knee prosthesis, temporary holders, and more. ZrO2 is used for a total hip replacement (THR), for an artificial knee joint as well as for the application and development of other medical devices. In order to use ZrO2Y2O3 ceramics (YSZ) in biomedical substrates, it is necessary to deposit coating layers without defects. For the purpose of the deposition of a ZrO28wt.%Y2O3 ceramic coating with the best structural properties, the ZrO2Y2O3 / ZrO2Y2O3CoNiCrAlY/ CoNiCrAlY coating system was tested. For financial reasons, the deposition was performed on a steel substrate by applying a CoNiCrAlY bond coating, which does not affect the structure and functionality of the ZrO2Y2O3 ceramic layer. The structure of the layers was tested by the method of light microscopy, and the surface of the upper ZrO28wt.%Y2O3 ceramic coating was tested by the method of scanning electron microscopy (SEM). The obtained characteristics showed that the porosity content in the ceramic layer was not high and that micropores were uniformly distributed. The mechanical properties of the layers were assessed by testing microhardness using the method HV03 and tensile bond strength using tensile testing.
ACKNOWLEDGEMENT: The author is thankful for the financial support from the Ministry of Education and Science of the Republic of Serbia (national projects OI 174004).
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The values of the microhardness of the ZrO28wt.%Y2O3 coating were satisfactory as well as the tensile bond strength of the coating system.
Keywords: ZrO2, Y2O3, property, microstructures, mechanical properties, layers, coatings, ceramics, bonding.
Introduction
Zirconium dioxide ZrO2 ceramics has one of the lowest thermal conductivity values, and is therefore widely used as a thermal insulator at elevated temperatures (Mrdak, et al., 2013, pp.559-567), (Mrdak, et al., 2015, pp.337-343), (Mrdak, 2016, pp.411-430). ZrO2Y2O3 ceramic coatings generally have excellent physical characteristics. Due to its stability, high biocompatibility and good physical properties such as high flexural strength of 900-1200 MPa, hardness of 1200 HV and Weibull modulus of 10-12, zirconium dioxide ZrO2 is widely used in the process of manufacturing implants (Piconi, Maccauro, 1999, pp.1-25). In recent years, research efforts have focused on developing the ZrO2-Y2O3 system as a biomaterial in orthopedic surgery for producing hip implant parts, characterized by the microstructure of a metastable tetragonal lattice (Piconi, Maccauro, 1999, pp.1-25). In order to use zirconium dioxide ZrO2 as a functional biomedical coating on substrates, ceramic coating layers must be deposited without defects. The first systems of ZrO2-Y2O3(YSZ) coatings stabilized with Y2O3 were of 12 - 20wt.%Y2O3, which fully stabilized the cubic c - phase. Later, tests showed that better performances can be achieved by reducing the levels of oxides Y2O3 to 8wt.%. The ZrO28%Y2O3 system is now widely used because it is standardized and has the status of an ISO standard for surgical application (ISO standard 13356, 2008, revision of a previous version of 1997). Tests of ZrO28%Y2O3 ceramic coatings have shown that they do not cause any cytotoxicity in living cells; therefore, they are biocompatible (Lang, Mertens, 1990, pp.606-611), (Dion, et al., 1994, pp.18-24). Previous studies and tests relate to the ZrO2Y2O3 system with 8wt.%Y2O3, which is most commonly used in practice, and deposited by APS and VPS depositing processes (Mrdak, 2015, pp.137-159). The coating has a lot of good features, such as a high coefficient of thermal expansion of 11 x 10-6K-1, a low density of 6.4 g/cm3, a low modulus of elasticity and high hardness, which provides better wear resistance. In addition, it has been proven that ZrO2 coatings with 8wt.%Y2O3 are corrosion resistant to body fluids, which makes them bioinert. Compared to other industrial applications, biomedical coatings are a relatively new class of applications (Weidian, 2006), (Wang, 2008),
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(Heimann, 2006, pp.2012-2019), (Hong, et al., 2004, pp.317-326). Types of coatings applied in the artificial knee joint are mainly: hydroxyapatite (HA), zirconium dioxide (ZrO2), aluminum oxide (Al2O3), titanium dioxide (TiO2) and chromium oxide (Cr2O3). Increasing demands for improved efficiency of hydroxyapatite (HA) have influenced the development of many types of multiphase biomedical coatings. Some of the developed coating systems are HA/ZrO2Y2O3(YSZ). Zirconium dioxide ZrO2Y2O3(YSZ) is one of the most important bioinert oxides which is used in manufacturing implants. The results showed that the addition of ZrO2Y2O3(YSZ) from 40 to 60vol.% to hydroxyapatite significantly reduces the decomposition of HA during the powder deposition by plasma spraying. A higher content of zirconium dioxide ZrO2Y2O3(YSZ) increases the proportion of crystalline HA, and reduces the proportion of the amorphous phase in the coating. ZrO2-Y2O3 ceramics reduces the share and size of pores in the coating and increases the coating hardness, wear resistance, adhesion, and cohesive strength when compared to a pure HA coating (Khor, et al., 2000, pp.160-166), (Morks Magdi, Kobayashi, 2007, pp.47-51). Biomedical coatings consist of at least two layers: bond / ceramic or more layers (bond / bond + ceramic / ceramic layer). In order to reduce stresses in the coating and at the interface between the substrate and the coating, three-layer coating systems are often produced.
For the deposition of the ZrO2Y2O3 coating with functional characteristics, the ZrO28wt.Y2O3(YSZ) powder was deposited in the ZrO2Y2O3 / ZrO2Y2O3CoNiCrAlY / CoNiCrAlY system; because of the economic effect, cheaper substrate and bonding coating were chosen since they do not affect the microstructure of the functional ZrO2Y2O3 coating. The bonding and cermet coatings were deposited by the VPS process, while the ZrO28wt.%Y2O3 ceramic coating was deposited by the APS process. This paper focuses on the testing of microhardness, microscopic and macroscopic defects in ZrO2Y2O3 coatings such as peeling of layers, pores on the coating surface, coarse unmelted particles, coarse pores, micro and macro cracks in the coating layers and on the coating surface, all of which have a negative impact on the mechanical properties of the ZrO2Y2O3 coating. The test results have shown that there are no coarse particles, macro pores, cracks and other defects on the surface of the ZrO2Y2O3 coating. The presence of a certain quantity of micro-pores in the ceramic coating is normal and the content of the pores in the coating was in accordance with the standards of this coating. The layers on the surface of the ZrO2Y2O3 coating show that powder particles are uniformly deformed and smooth and as such can be applied in the field of biomedicine.
Materials and experimental details
To create a three-layer coating, the Sulzer Metco powder types marked AMDRY 9951 and Metco 204F were used. The AMDRY 9951 powder is a superalloy Co32Ni21Cr8Al0.5Y. The powder particles are spherical, which provides a good flow of the plasma jet. Figure 1 shows the scanning electron micrographs (SEM) of the morphology of powder particles. The granulation range of powder particles was from 5 jm to 37 |jm (Material Product Data Sheet, 2011, AMDRY 9951, Cobalt Nickel Chromium Aluminum Yttrium (CoNiCrAlY) Thermal Spray Powders, DSMTS - 0092.1, Sulzer Metco).
Figure 1 - (SEM) Scanning electron micrography of CoNiCrAlY powder particles Рис. 1 - (SEM) Электронная микрография частиц порошка CoNiCrAlY Слика 1 - (SEM) Скенинг електронска микрограф^а честица праха CoNiCrAlY
A mechanical mixture of AMDRY 9951 and Metco 204F powders (35% (Co32Ni21Cr8Al0.5Y) + 65% (ZrO28wt.%Y2C>3)) was used to produce a transitional cermet layer. The upper ceramic coating was produced from Metco 204F (ZrO28wt.%Y2O3) powder. The powder was produced by the method of agglomeration and HOSP granulation from 15 jm to 45 jm. Figure 2 shows the scanning electron micrographs of the morphology of ZrO28wt.%Y2O3 powder particles. The powder particles have a regular spherical shape (Material Product Data Sheet, 2012, Metco 204F, 8% Yttria Stabilized Zirconia Agglomerated and HOSP™ Thermal Spray Powders, DSMTS-0001.2, Sulzer Metco).
The material on which the coating layers were deposited was X15Cr13 stainless steel (EN 1.4024) in the untreated condition. The mechanical characteristics of the coating layers were tested in accordance with the Pratt & Whitney standard (Turbojet Engine - Standard Practices
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Manual (PN 582005), 2002, Pratt & Whitney, East Hartford, USA). The substrates on which coatings were sprayed for microhardness testing and evaluation of the microstructure in the deposited condition were made of steel C.4171 (X15Cr13 EN10027) in a thermally unprocessed condition with the dimensions 70x20x1.5mm.
Figure 2 - (SEM) Scanning electron micrography of ZrO2 8%Y2O3 powder particles
Рис. 2 - (SEM) Электронная микрография частиц порошка ZrO2 8%Y2O3 Слика 2 - (SEM) Скенинг електронска микрограф^а честица праха ZrO2 8%Y2O3
The substrates for testing bond strength were made of the same steel in the untreated condition with the dimensions 025x50mm. The microhardness of the layers was tested by the method HV03 and their bond strength by tensile testing.
The microstructure of the deposited layers was examined under a light microscope. The share of micro pores in the coating was analysed by treating 5 photos at 200x magnification. This paper presents the mean values of the share of pores in the coating.
The bonding and cermet coating powders were deposited with the vacuum plasma spray system of the Plasma Technik AG company and with an F - 4 plasma gun, with controlled plasma spray parameters. The powders were deposited with a mixture of plasma gases Ar-H2. Before the deposition of bonding and cermet coating powders, the substrate surface was cleaned with a transferred arc with a mixture of gases Ar-He. The CoNiCrAlY bonding coating powders were deposited with the optimum deposition parameters (Mrdak, 2013, pp.26-47). Table 1 shows the VPS parameters of powder deposition. The bonding layers were deposited with a thickness of 50 jim - 60jim and the cermet layers with a thickness of 100 |jm - 110 |jm.
The deposition of Metro 204F (ZrO28wt.% Y2O3) ceramic powders was performed with an atmospheric plasma spray system of the
Plasmadyne company and with an SG-100 plasma gun, with controlled plasma spray parameters. The SG -100 plasma gun consisted of a cathode type K 1083 - 129, anode type A 1083-165 and a gas injector type GI 1083 - 113. Ar was used as an arc gas in combination with He and the power supply of up to 40 KW.
Table 1 - VPS plasma spray parameters Таблица 1 - VPS параметры плазменного напыления Табела 1 - VPS плазма cnpej параметри
Parameters Values
Cleanin g arc Spraying CoNiCrAlY 35% (CoNiCrAlY) + 65%(ZrO2Y2O3 )
Plasma current, I (A) 500 700 750
Plasma voltage, U (V) 65 60 74
Primary plasma gas flow rate Ar, l/min 50 50 50
Secondary plasma gas flow rate He (1), H2 , l/min 10 (1) 9 (2) 9 (2)
Carrier gas flow rate, l/min -- 3 3
Powder feed rate, g/min -- 40 50
Stand-off distance, mm 270 270 270
Chamber pressure, mbar 25 120 120
Nozzle diameter (mm) 8 8 8
Speed of the gun, mm /s 15 15 15
The plasma spray powder deposition parameters are shown in Table 2. The upper ZrO28wt.% Y2O3 ceramic layers were deposited with a thickness of 250 ^m - 270 ^m.
Table 2 - The parameters of the deposition of the ZrO28wt.%Y2O3 powder Таблица 2 - Параметры напыления порошка ZrO28wt.%Y2O3 Табела 2 - Параметри депозите праха ZrO28wt.%Y2O3
Parameters Metco 204F
Plasma current, I (A) 900
Plasma voltage, U (V) 43
Primary plasma gas flow rate Ar , l/min 47
Secondary plasma gas flow rate He, l/min 32
Carrier gas flow rate Ar, l/min 6
Powder feed rate, g/min 50
Stand-off distance, mm 80
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Results and discussion
The values of the coating system microhardness are shown in Figure 3. The bonding coating - BC (CoNiCrAlY) had microhardness values from 595 to 610HV03. The measured values of the bonding coating microhardness were uniform, which indicates that a small proportion of micropores was present in the coating, also confirmed by an image analysis. The layers of the cermet coating - BC/CC (ZrO2Y2O335 CoNiCrAlY%) had slightly higher values of microhardness due to the content of ceramics; the values were rather uniform and in a range from 620 to 660HV0.3.
The deposition of powder particles by the VPS process at low pressure made it possible to produce thicker layers of bonding and cermet coatings with more consistent microhardness values. The ceramic coating - CC (ZrO28% Y2O3) deposited by the APS process at atmospheric pressure had the highest microhardness values in a range from 690 to 760HV03. Due to high melting temperature, ceramic powder particles were semi-molten in the core and, in a collision with a previously deposited layer, they were plastically deformed achieving inter-lamellar contacts followed by the formation of inter lamellar pores, which is characteristic for ceramics. Figure 3 shows the minimun and maximum microhardness values of the ZrO2Y2O3 / ZrO2Y2O3CoNiCrAlY / CoNiCrAlY coating system.
Figure 3 - Microhardness of ZrO2Y2O3 / ZrO2Y2O3CoNiCrAlY / CoNiCrAlY coatings Рис. 3 - Микротвердость покрытия ZrO2Y2O3 / ZrO2Y2O3CoNiCrAlY / CoNiCrAlY Слика 3 - Микротврдо^а ZrO2Y2O3 / ZrO2Y2O3CoNiCrAlY / CoNiCrAlY превлака
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The mean value of the coating system strength was 68 MPa. The application of a transferred arc made the substrate surface clean and reactive with deposited powder particles. Powder particles deposited in vacuum achieve good contact inter-lamellar bonding as well as good bonding with the substrate. The values of microhardness and tensile strength of the coating system were in correlation with the microstructure of the deposited layers. Figures 4 and 5 show the microstructures of the coating layers.
Figure 4 - The microstructure of the ZrO2Y2O3 / ZrC^OaCoNiCrAlY / CoNiCrAlY coating Рис. 4 - Микроструктура покрытия ZrO2Y2O3 / ZrO2Y2O3CoNiCrAlY / CoNiCrAlY Слика 4 - Микроструктура превлаке ZrO2Y2O3 / ZrO2Y2O3CoNiCrAlY / CoNiCrAlY
Figure 5 - The microstructure of the ZrO2Y2O3 / ZrO2Y2O3CoNiCrAlY / CoNiCrAlY coating Рис. 5 - Микроструктура покрытия ZrO2Y2O3 / ZrO2Y2O3NiCoCrAlY / CoNiCrAlY Слика 5 - Микроструктура превлаке ZrO2Y2O3 / ZrO2Y2O3NiCoCrAlY / CoNiCrAlY
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The micrographs clearly show the interfaces between the substrates and the bonding layers, the bonding coating and the cermet coating as well as between the cermet coating and the ceramic coating. A metallographic analysis of the coatings showed that the bond between the bonding coating and the substrate is good without the presence of microcracks and macro cracks in the interface. The bond of the coating with the substrate is uniform without a separation and peeling of the coating from the substrate. The analysis of the micrographs showed that the share of micro pores was less than 1% in the bonding coating layers. The share of micro pores in the cermet coating layers was 2%, and in the ZrO28wt.% Y2O3 ceramic coating layers it was 7%. In the bonding coating layers, lamellae of deposited powder particles cannot be seen due to good melting and good interface between the deposited particles. There are no unmelted particles, precipitates and oxides in the coating since the vacuum plasma spraying process allows the deposition of layers without oxide content. Black micropores smaller than 10 ^m can be seen throughout the bonding coating layers. The CoNiCrAlY coating in the deposited state comprises two phases, y and p. The coating base consists of the y phase which is a solid solution of Co, Ni, Cr and the p (Co,Ni)Al phase (Cheruvu, et al., 2000, pp.50-54), (Mobarra, et al., 2006, pp.22022207), (Mrdak, 2013, pp.26-47), (Poza, Grant, 2006, pp.2887-2896). The middle cermet inter-layer is continuously deposited on the bonding coating. Dark gray ceramic coating lamellae uniformly distributed among light gray lamellae of the bonding coating are clearly visible throughout the cermet layer (Fig.6). Black micro pores up to 10 ^m can be seen in the cermet layer (Fig.5). The upper ceramic layer is deposited uniformly on the cermet layer in which black micro pores can be seen (Fig 4).
Figure 7 shows a SEM micrograph of the surface of a completely molten ZrO28wt.% Y2O3particle. The SEM analysis of the morphology of the surface of a deposited ceramic powder particle shows that it is smooth, indicating that it is completely molten and properly deposited on the previously deposited ceramic layer.
The surface of a completely molten ZrO2Y2O3 particle is circled in red in the SEM micrograph. Because of complete melting, a powder particle formed a regular geometric shape when colliding with the surface. The microstructure shows fine precipitates of irregular shapes up to 10 ^m, circled in yellow. The SEM micrograph clearly shows fine black micro pores, irregularly shaped, up to 5 ^m in size (circled in green).
Figure 6 - The VPS microstructure of the CoNiCrAlY + ZrO2Y2O3 coating Рис. 6 - Микроструктура покрытия VPS CoNiCrAlY + ZrO2Y2O3 Слика 6 - Микроструктура VPS CoNiCrAlY + ZrO2Y2O3 превлаке
Figure 7 - (SEM) Surface morphology of the ZrO2Y2O3 coating Рис. 7 - (SEM) Морфология поверхности покрытия ZrO2Y2O3 Слика 7 - (SEM) Морфологи]а површине ZrO2Y2O3 превлаке
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Conclusion
In this study, the plasma spray process produced a coating system of ZrC^Os / ZrC^OsCoNiCrAlY / CoNiCrAlY. The bonding coating and the cermet coating were deposited by the vacuum plasma spray process. The upper functional ZrO2Y2O3 ceramic coating was deposited by the atmospheric plasma spray process. The paper analyzes the structure and the mechanical properties of the coatings in the deposited state, based on which the following conclusions were made.
The coating system had good mechanical properties with the following microhardness values: the bonding layer from 595 to 610HV03, the transitional cermet layer from 620 to 660HV03 and the upper ceramic layer from 690 to 760HV03. The bonding and cermet coatings had a quite uniform microhardness, allowed by the VPS process at low pressure. The ZrO28% Y2O3 ceramic coating deposited by the APS process at atmospheric pressure had the highest microhardness value with a range of 70HV03. The bond strength of the coating system had a high value of 68MPa. The application of the transferred arc provided a good adhesive bond of molten particles with the substrate and a good cohesive bond between deposited lamellae.
The analysis of the micrographs showed that the share of pores in the bonding coating was less than 1%, in the layers of the cermet coating it was 2%, and in the ZrO28wt.% Y2O3 ceramic coating it was 7%. The microstructure of the bonding coating shows a lamellar structure due to good melting of powder particles and a good interface of deposited particles. The middle cermet layer is continuously deposited on the bonding coatings. Dark gray lamellae of the ceramic coating are clearly visible throughout the cermet coating as well as micropores in black.
The ZrO2Y2O3 ceramic layer is evenly deposited on the cermet layer. In the ZrO2Y2O3 ceramic coating and on the surface there are no defects such as coarse unmelted particles, coarse pores, micro cracks and macro cracks and other defects which have a negative effect on the mechanical properties and functionality of the coating. The surface of the ZrO2Y2O3 coating shows that powder particles are regularly deformed and smooth and as such are suitable for the application in biomedicine.
Based on the obtained mechanical and structural characteristics of the ZrO2Y2O3 coating, it was found that the quality of the coating makes it suitable for use with other materials in creating a system of biomedical coatings.
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МЕХАНИЧЕСКИЕ ХАРАКТЕРИСТИКИ И МИКРОСТРУКТУРА ПОКРЫТИЙ ZrO2Y2O3 / ZrO2Y2O3CoNiCrAlY / CoNiCrAlY, НАНЕСЕННЫХ ВОЗДУШНО-ПЛАЗМЕННЫМ НАПЫЛЕНИЕМ
Михаило Р. Мрдак
Центр исследований и развития А.О. «ИМТЕЛ коммуникации», Белград, Республика Сербия
ОБЛАСТЬ: химические технологии
ВИД СТАТЬИ: оригинальная научная статья
ЯЗЫК СТАТЬИ: английский
Резюме:
Керамика ZrO2 стабилизированная оксидом иттрия Y2O3 обладает наилучшими характеристиками по сравнению с иными современными керамическими материалами. Благодаря высокому проценту биосовместимости, керамика ZrO2 в системе ZrO2-Y2O3 широко применяется в качестве биоматериалов в ортопедической хирургии. Керамика ZrO2 используется в области протезирования, в частности, для изготовления головки бедренной кости, колени, временного протеза и пр. В области медицины ZrO2 широко используется в изготовлении протеза бедра (THR), коленного сустава, и иных медицинских аппаратов. Нанесение керамического покрытия ZrO2Y2O3(YSZ) на биомедицинские субстраты должно быть равномерным, а его слои без изъянов. Для нанесения керамического покрытия ZrO2Y2O3(YSZ), обладающего
наилучшими структурными характеристиками была испытана система покрытий ZrO2Y2O3/ZrO2Y2O3CoNiCrAlY/CoNiCrAlY. В целях экономии, напыление выполнено на стальном субстрате связывающим покрытием CoNiCrAlY, не влияющим на структуру и функциональность керамического слоя ZrO2Y2O3. Структура слоев испытана методом оптической микроскопии, а поверхность ZrO28mas%Y2O3 испытана методом электронной микрографии (SEM). На основании полученных характеристик установлено, что содержание порообразований в керамическом слое достаточно низкое, а микропоры равномерно распределены. Анализ механических характеристик покрытия проведен на основании испытаний микротвердости методом HV03 и прочности соединений методом растяжения. Значения микротвердости ZrO28mas%Y2O3 покрытия соответствуют требованиям, так же как и прочность связи покрытий.
Ключевые слова: ZrO2, Y2O3, свойства, микроструктура, механические характеристики, слои, покрытие, керамика, соединения.
МЕХАНИЧКЕ ОСОБИНЕ И МИКРОСТРУКТУРА ПЛАЗМА НАПРСКАНЕ ПРЕВЛАКЕ ZrO2Y2O3 / ZrO2Y2O3CoNiCrAlY / CoNiCrAlY
Михаило Р. Мрдак
Истраживачки и разверни центар ИМТЕЛ Комуникаци]е а. д., Београд, Република Срби]а
ОБЛАСТ: хеми]ске технологи]е
ВРСТА ЧЛАНКА: оригинални научни чланак
JЕЗИК ЧЛАНКА: енглески
Сажетак:
Керамика ZrO2 стабилизована са Y2O3, има супериорна и одлична физичка сво}ства у поре^ек>у са другим савременим керамичким матерщалима. Због високе биокомпатибилности она у систему ZrO2-Y2O3 има широку примену као биоматери}ал у ортопедскоj хирурги]и. Керамика ZrO2-Y2O3 на]чешЬе се примере за израду глава кука, протеза колена, привремених држача итд. ZrO2 jе у клиничко] употреби као укупна замена кука (THR), у зглобу вештачких колена, али се користи за примену и развоj других медицинских уре^а]а. Да би се керамика ZrO2Y2O3(YSZ) користила на биомедицинским субстратима, неопходно jе депоновати сло}еве превлаке без дефеката. Ради депозици}е керамичке превлаке ZrO28теж%Y2O3 са на]бол>им структурним сво}ствима, испитан }е систем превлака ZrO2Y2O3/ZrO2Y2O3CoNiCrAlY/CoNiCrAlY. Због економичности депозици}а jе извршена на челичном супстрату уз примену везне превлаке CoNiCrAlY, што не утиче на структуру и
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функционалност керамичког сло]а ZrO2Y2O3. Структура сло]ева испитана je методом светлосне микроскопце, а површина гор^е керамичке превлаке ZrO28мас%Y2O3 методом скенинг електронске микроскопи]е (SEM). На основу доби}ених карактеристика утвр^ено jе да садржаj порозности у керамичком сло}у ни]е био висок и да су микропоре равномерно распоре^ене. Процена механичких особина сло}ева ура^ена jе испитива^ем микротврдоЯе методом HV03 и затезне чврстоЬе спо]а испитива^ем на затеза^е. Вредности микротврдоЬе ZrO28мас%Y2O3 превлаке биле су задоволава]уПе и затезна чврстоЬа спо]а система превлака.
К^учне речи: ZrO2, Y2O3, сво}ство, микроструктуре, механичка сво}ства, сло}еви, превлаке, керамике, везива^е.
Paper received on / Дата получения работы / Датум приема чланка: 28. 03. 2016. Manuscript corrections submitted on / Дата получения исправленной версии работы / Датум достав^а^а исправки рукописа: 02. 04. 2016.
Paper accepted for publishing on / Дата окончательного согласования работы / Датум коначног прихвата^а чланка за об]ав^ива^е: 04. 04. 2016.
© 2017 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/).
© 2017 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/).
© 2017 Аутор. Обjавио Воjнотехнички гласник / Vojnotehnicki glasnik / Military Technical Courier (www.vtg.mod.gov.rs, втг.мо.упр.срб). Ово jе чланак отвореног приступа и дистрибуира се у складу са Creative Commons licencom (http://creativecommons.org/licenses/by/3.0/rs/).
