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9SYNTHESIS OF NANOSTRUCTURED COATINGS WITH SIMULTANEOUS SPUTTERING OF
VARIOUS CATHODES AND TARGETS
Yurov V.,
Candidate of Physical and Mathematical Sciences
Associate Professor Karaganda University named after E.A. Buketova Karaganda, Kazakhstan Berdibekov A., Doctor of philosophy (PhD) National Defense University named after the First President of the republic of Kazakhstan - Elbasy Kazakhstan, Nur-Sultan
Belgibekov N.
Master, LLP "Research & Development center "Kazakhstan engineering" Kazakhstan, Nur-Sultan
Abstract
The combined methods of surface treatment for obtaining heat-resistant coatings, proposed by us, consist in a combination of various kinds of influences on the material being processed. For example, the nitriding process is combined with the preliminary activation of the surface by means of an electric discharge in an inert gas medium. This makes it possible to intensify the process of diffusion saturation, to increase the depth of the modified layer and its microhardness. Similar goals are also achieved with a combination of gas nitriding and pretreatment of the product surface with laser radiation. We associate the radiation resistance of the Zn-Al coating with its pronounced globular structure. The presence of such a system of "balls" leads to elastic scattering of argon ions, so that the local deformation turns out to be insignificant.
Keywords: nanostructure, coatings, surface, nitriding, deformation, microhardness, modified layer, nitrogen, argon.
Introduction
In modern conditions, the production of competitive mechanical engineering products and their effective renovation are impossible without the use of strengthening technologies, especially those that allow the formation of layers or coatings on the surface of products, characterized by increased performance characteristics, primarily increased wear resistance.
Let us list these methods [1-4]: heat treatment, cryogenic, cutting, electrochemical polishing, diffusion saturation of a non-metal, diffusion metallization, diffusion saturation with a complex of elements, surface heat treatment, mechanical processing by plastic deformation, electrophysical treatment, surfacing with alloyed metal, spraying, chemical deposition, electrochemical deposition, electrophysical methods, deposition of hard coatings from the vapor phase, processing in a magnetic field. The listed methods belong to the class of hardening treatment [1-4]: hardening by changing the structure of the entire volume of the product, hardening by changing the surface roughness, hardening by changing the chemical composition of the surface layer of the metal, hardening by changing the structure of the surface layer, hardening by applying coatings on the surface, hardening by changing the energy reserve of the surface layer. The combined methods of surface treatment for obtaining heat-resistant
coatings, proposed by us, consist in a combination of various kinds of effects on the processed material [510]. For example, the nitriding process is combined with the preliminary activation of the surface by means of an electric discharge in an inert gas medium. This makes it possible to intensify the process of diffusion saturation, to increase the depth of the modified layer and its microhardness. Similar goals are also achieved with a combination of gas nitriding and pretreatment of the product surface with laser radiation. Preliminary production tests have shown the promise of using a coating formed by Cr-Mn-Si-Cu-Fe-Al+Ti in a nitrogen atmosphere by magnetron sputtering followed by laser treatment.
Synthesis of nanostructured coatings with simultaneous sputtering of various cathodes and targets
We carried out studies of the microstructure of coatings using composite targets of the composition: Cr-Mn-Si-Cu-Fe-Al, Zn-Al, Fe-Al, Zn-Cu-Al, Mn-Fe-Cu-Al and a titanium cathode sprayed by the CIB method. Figures 1 and 2 show an electron microscopic image and XPS of a Cr-Mn-Si-Cu-Fe-Al + Ti coating in an argon atmosphere. Titanium grains with a size from 1 to 10 microns in diameter are clearly visible. Materials with such a grain size are usually called coarse-crystalline [4].
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Figure 1 - SEM coating Cr-Mn-Si-Cu-Fe-Al + Ti in argon
Table 1 shows the results of a quantitative analysis, Al is less than 1 mass. %.
Table 1
Results of quantitative analysis of the Cr-Mn-Si-Cu-Fe-Al + Ti coating in argon at various points on the surface
Figure 2 - XPS coating Cr-Mn-Si-Cu-Fe-Al + Ti in argon
from which it follows that the content of Mn, Si, Cu and
001 002
Element (keV) Mass% Error% Atom% Element (keV) Mass% Error% Atom%
Ti K 4.508 49.45 0.25 52.24 C K 0.277 7.96 0.04 26.69
Cr K 5.411 42.59 0.45 41.45 Ti K 4.508 48.80 0.24 41.03
Fe K 6.398 5.89 0.62 5.33 Cr K 5.411 40.24 0.43 31.16
Ag L 2.983 2.07 0.34 0.97 Ag L 2.983 3.01 0.33 1.12
Total 100.00 100.00 Total 100.00 100.00
003 004
Element (keV) Mass% Error% Atom% Element (keV) Mass% Error% Atom%
C K 0.277 7.17 0.05 23.81 C K 0.277 3.96 0.05 14.56
Ti K 4.508 78.97 0.29 65.72 Ti K 4.508 54.75 0.26 50.50
Cr K 5.411 11.16 0.52 8.55 Cr K 5.411 38.81 0.47 32.98
Fe K *6.398 2.70 0.69 1.92 Fe K 6.398 2.48 0.65 1.96
Total 100.00 100.00 Total 100.00 100.00
In a nitrogen environment, the structure of the coating changes dramatically (Figures 3 and 4), due to the formation of titanium nitride. In this case, the average grain size is (100-150) nm. Such coatings are called submi-crocrystalline [4].
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Figure 3 - SEM coating Cr-Mn-Si-Cu-Fe-Al + Ti in nitrogen
Table 2 shows the results of quantitative analysis of Cr-Mn-Si-Cu-Fe-Al + Ti in nitrogen at various points on the surface, from which it follows that the content of chromium, titanium and nitrogen are close to each other. This suggests that, in addition to the for-
Figure 4 - XPS coating Cr-Mn-Si-Cu-Fe-Al + Ti in nitrogen
mation of titanium nitride, chromium nitride is also being formed. Figure 3 shows that microcrystallites of titanium and chromium nitrides have an orientation (presumably in the (200) direction), which is also different from the spherical symmetry of microcrystallites of pure titanium.
Table 2
The results of the analysis of the Cr-Mn-Si-Cu-Fe-Al + Ti coating in a nitrogen atmosphere
022 023
Element (keV) Mass% Error% Atom% Element (keV) Mass% Error% Atom%
C K 0.277 10.07 0.04 20.74 C K 0.277 8.44 0.05 17.89
N K 0.392 27.20 0.19 48.04 N K 0.392 26.93 0.20 48.94
Ti K 4.508 33.90 0.26 17.51 Ti K 4.508 36.46 0.29 19.38
Cr K 5.411 28.83 0.45 13.72 Cr K 5.411 28.16 0.50 13.79
Total 100.00 100.00 Total 100.00 100.00
024
Element (keV) Mass% Error% Atom%
C K 0.277 9.31 0.04 18.52 -
N K 0.392 30.84 0.18 52.62
Ti K 4.508 34.69 0.25 17.31
Cr K 5.411 25.16 0.45 11.56
Total 100.00 100.00
The structure of the coating can be changed using ion bombardment. Figures 5 and 6 show the electron microscopic image and XPS of the Cr-Mn-Si-Cu-Fe-Al + Ti coating in argon after ion bombardment. The irradiation of the coatings with argon ions was carried out using a multi-ampere ion source with a hollow cathode. The current in the arc was 1 A, and the potential on the
substrate was maintained at 300 V. In this case, the grain size is less than 100 nm and such a structure is usually called nano-crystalline [4]. Ion bombardment offers great opportunities for regulating the structure and properties of coatings and is often used to create various combined deposition methods.
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Figure 5 - SEM coating Cr-Mn-Si-Cu-Fe-Al + Ti in argon after ion bombardment
Figure 6 - XPS coating Cr-Mn-Si-Cu-Fe-Al + Ti in argon after ion bombardment
In the case of binary cathodes, the situation is somewhat different (Figures 7-10). The average size of the titanium phase in the Fe-Al + Ti coating in argon is smaller than in the coating Cr-Mn-Si-Cu-Fe-Al+Ti. In a nitrogen environment, smaller sizes of titanium nitride crystallites are also observed.
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Figure 7 - SEM coating Fe-Al + Ti in argon environment
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Figure 8 - XPS coating Fe-Al + Ti in argon
Figure 9 - SEM coating Fe-Al + Ti in nitrogen environment
Figure 10 - XPS coating Fe-Al + Ti in nitrogen
For the Zn-Al + Ti coating, large grain sizes of crystallites are observed (Figures 11-12).
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Figure 11 - SEM coating Zn-Al + Ti in argon environment
Figure 12 - SEM coating Zn-Al + Ti in nitrogen atmosphere
In general, the structure of the Fe-Al and Zn-Al coatings at the nanoscale is significantly different (Figures 13 and 14). In the first case, an open dissipative structure is observed, and in the second, a globular structure.
Figure 13
AFM image of the surface of the Fe-Al coating
Ionic bombardment of the Fe-Al + Ti and Zn-Al + Ti coatings does not lead to a crushing of the grain structure, as is observed for the Cr-Mn-Si-Cu-Fe-Al +
Figure 15 - AFM image of the Fe-Al coating surface after irradiation with argon ions
Figure 14
AFM image of the surface of the Zn-Al coating
Ti coating. It's related with the fact that ion irradiation has little effect on the coatings Fe-Al and Zn-Al. This is clearly seen from Figures 15 and 16.
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Figure 16 - AFM image of the surface of the Zn-Al coating after irradiation with argon ions
We associate the radiation resistance of the Zn-Al coating with its pronounced globular structure (Figure 14). The presence of such a system of "balls" leads to elastic scattering of argon ions, so that the local deformation turns out to be insignificant. This is reflected in the behavior of Young's modulus, which does not change during irradiation, and in the roughness parameter. The radiation resistance of the Fe-Al coating is associated with the disorder of its structure. The presence of strong "amorphization" of the coating makes it radiation-insensitive.
It should be noted that a decrease in the thickness of the coating to nanosize strongly affects the thermal and time stability of their properties. For example, it was shown in [11] that relaxation processes in nanostructured multilayer TiN-ZrN films proceed even at room temperature, which manifested itself in a significant decrease in hardness after long-term storage. Single-layer nanostructured condensates obtained under conditions of ion bombardment also have low stability. Ion bombardment leads not only to grain refinement, but also to an increase in the density of defects (dislocations, etc.), the formation of compressive stresses [4].
Further research prospects are as follows
At present, it is nanocomposites that are the most promising materials for creating stable nanostructures. In the future, high-quality nanostructured coatings can be obtained by optimizing the coating composition by adjusting the energy of the deposited ions, the substrate temperature, the composition and pressure of the working gas, and other technological parameters of the deposition process. However, even greater efforts are to be made in this direction.
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