RU2215819C2 - Abrasion-resistant cover for articles with conjugable surfaces - Google Patents

Abstract

FIELD: chemical technology. SUBSTANCE: cover of internal surface of article comprises Ti_xAl_1-xN, wherein value x is in the limits from 0.1 to 0.2. Cover of external surface of article comprises Ti_tAl_1-tN, wherein value t is in the limits from 0.8 to 0.9 and it comprises Zr_yAl_1-yN, additionally wherein value y is in the limits from 0.2 to 0.3. Invention can be used in applying cover on articles forming friction pair by electric arc discharge in atmosphere of chemically inert gases. Invention provides the enhancement of safety in working friction pair using proposed covers. EFFECT: valuable properties of covers. 2 cl, 6 tbl, 1 ex

Description

 The invention relates to the field of coating on machine parts using an electric arc discharge in the atmosphere of chemically active gases and can be used in mechanical engineering, space engineering and automotive.

 It is known that titanium carbide (TiC) -based coatings are applied by chemical vapor deposition (CVD) on a bearing shell, and titanium nitride (TiN) coatings are coated on bearing balls by physical vapor deposition (PVD) (Symposium of the USSR State Committee in Science and Technology, House of Scientific and Technical Propaganda, Moscow and Leibold-Goreus (Germany), under the editorship of Dr. Detlev Repenning, p. 9, 1986).

 However, as production tests have shown, applying a “hollow cylinder” of friction to a titanium carbide coating on a friction pair and titanium nitride coatings to the rod is characterized by a high coefficient of friction and low wear resistance compared to expected.

The reason for the low efficiency of this pair is that the product is hollow cylinder is coated with titanium carbide by vapor deposition. A titanium carbide coating is applied to a steel substrate at a temperature of 1000 ^{° C.} , in this case, iron and chromium diffuse from the substrate into the coating. In addition, the titanium carbide coating has a coarse-grained structure and high surface roughness.

The TiN coating, which is applied to the steel substrate at a temperature of 500 ^{° C.} , has a fine-grained structure. Due to the fact that the titanium carbide coating has high hardness and roughness, as well as iron is present in the coating, the running-in of the friction pair does not occur. High surface roughness and high hardness lead to an increase in the coefficient of friction and wear of the part with a wear-resistant coating having lower microhardness. Known friction pair is characterized by low tribological characteristics and operational properties.

 The closest to the claimed technical solution for the technical purpose and the achieved result is the use of a coating of titanium nitride in the finger-disk system. Studies conducted on the samples show a fairly high performance both in vacuum and in air (the journal "Powder metallurgy", 30, 1987, p. 5).

 However, as production tests showed, the coating of titanium nitride on a friction pair "hollow cylinder" - the rod does not provide the specified performance, due to the following reasons.

 The coating of titanium nitride on the inner surface of the hollow cylinder does not provide the specified coating thickness. In addition, the inner coating layer has insufficient adhesion to the substrate.

 Therefore, when the rod moves along the inner surface of the sleeve due to poor adhesion, the coating is easily removed and friction occurs between the titanium nitride powder exfoliated from the inner surface and the coating applied to the outer surface of the rod.

 In this case, the friction coefficient (μ) increases, and the service life of this pair decreases.

 The objective of the proposed technical solution is to increase the reliability of parts with mating surfaces.

The task is achieved by selecting the optimal combination of coating the outer surfaces and the inner surfaces of the mating parts. For this, it contains Ti _x Al _1-x N as titanium nitride, where x = 0.1 - 0.2, while the outer surface coating contains Ti _t Al _1-t N as titanium nitride, where t = 0.8 - 0.9, and also additionally contains Zr _y Al _1-y N, where y = 0.2 - 0.3. In addition, the coating composition for the outer surfaces of parts with mating surfaces contains input components in the following ratio by weight percent: Ti _t Al _1-t N - 70-80%; Zr _y Al _1-y N - 20-30%.

Since the coating of titanium nitride by an electric arc method on the inner surface of the cylinder is practically impossible, in order to improve adhesion, the coating is applied by simultaneously evaporating titanium and aluminum in a nitrogen environment. In this case, the composition of the coating Ti _x Al _1-x N was experimentally selected, where x = 0.1 - 0.2. The resulting coating has high penetration and provides high adhesion between the coating and the substrate.

The introduction of a small amount of aluminum into the titanium plasma in a nitrogen medium deposited on the outer surface of the mating parts leads to the formation of Ti _t Al _1-t N, where t = 0.8 - 0.9, with properties similar to those of titanium nitride. However, due to the significant difference between the linear expansion coefficients of the pores of the coating and the substrate, peeling of the coating is possible. This ultimately leads to an increase in the coefficient of friction and a decrease in operational properties. Therefore, in addition to Ti _t Al _1-t N, Zr _y Al _1-y N is also introduced into the coating consisting of titanium nitride, where y = 0.2 - 0.3.

The introduction of the additive Zr _y Al _1-y N by simultaneous evaporation of zirconium and aluminum results in a particularly fine-grained structure with a grain size equal to 50 Nm or 5x10 ^-2 microns. By introducing Zr _y Al _1-y N, the adhesion between the coating and the substrate increases. In addition, the optimal ratio between the additionally introduced Ti _t Al _1-t N and Zr _y Al _1-y N equal to 70-80% (by weight) Ti _t Al _1-t N and 30-20% (by weight) was determined Zr _y Al _1-y N.

 Justification of the claimed physico-chemical composition of the coating for the inner surfaces of the mating parts.

To substantiate the claimed physicochemical composition of the coating, samples of 20 × 20 × 10 mm in size, made, for example, of 12X1810T stainless steel, were coated with 7 different coating compositions with a thickness of 3 to 5 μm. Then, the adhesion strength of the coating to the stainless substrate was determined by sclerometry. The criterion for high-quality coating is a critical normal force of at least 45 N, that is, this is the adhesion value of a Ti _x Al _1-x N coating deposited by physical vapor deposition of the willow gas.

 The test results are presented in table 1.

As can be seen from the data in Table 1, only the coating of the physicochemical composition Ti _x Al _1-x N, where x = 0.1 - 0.2, provides sufficient adhesion, and when these limits are exceeded, the critical normal force decreases, t. e. the adhesion of the coating or adhesion decreases.

 Justification of the claimed physico-chemical composition of the coating for the outer surfaces of parts with mating surfaces.

According to the claimed technical solution, Ti _t Al _1-t N, where t = 0.8 - 0.9, and Zr _y Al _1-y N, where y = 0.2 - are additionally introduced into the coating composition consisting of titanium nitride 0.3.

Initially determined necessary in the composition the content of Ti _t Al _1-t N. To substantiate the claimed physico-chemical composition of the coating on samples measuring 20h20h10 mm, made for example of stainless steel 12X18H10T, 7 different formulations applied coating thickness of 3 to 5 microns . Then, the adhesion strength of the coating to the stainless substrate was determined by sclerometry. The criterion for high-quality coating is a critical normal force of at least 35 N, that is, this is the adhesion value of a Ti _t Al _1-t N coating deposited by physical vapor deposition.

 The test results are presented in table 2.

As can be seen from table 2, the coating, consisting of Ti _t Al _1-t N, where t = 0.8 - 0.9, provides sufficient adhesion for application to the outer surface, but does not provide a given grain size equal to 100-150 microns . Therefore, to obtain a fine-grained structure with a grain size equal to 50 Nm, Zr _y Al _1-y N is additionally introduced into the coating, where y = 0.2 - 0.3, which allows to increase the adhesion strength of the coating to the surface of the part.

Justification of the boundary values of the component Zr _y Al _1-y N, where y = 0.2 - 0.3.

To justify the claimed physicochemical composition of the coating, samples of 20 × 20 × 10 mm in size, made, for example, of stainless steel 12X18H10T, were coated with 7 different coating compositions with a thickness of 3 to 5 μm at t = 0.8 in Ti _t Al _1-t N. Then, the adhesion strength of the coating to the stainless substrate was determined by sclerometry. The criterion for high-quality coating is a critical normal force of at least 42 H, that is, this is the adhesion value of a Ti _t Al _1-t N coating deposited by physical vapor deposition.

 The test results are presented in table 3.

As can be seen from the table, Zr _y Al _1-y N with y = 0.2 - 0.3 added to the coating provides the necessary adhesion of the coating to the substrate, and when the value of "y" exceeds the specified limits, the adhesion of the coating decreases.

The rationale for the percentage of Ti _t Al _1-t N and Zr _y Al _1-y N in the claimed physico-chemical composition of the coating.

To justify the claimed physicochemical composition of the coating, samples of 20 × 20 × 10 mm in size, made, for example, of 12Kh18N10T stainless steel, were coated with 7 different coatings of Ti _0.8 Al _0.2 N and Zr _0.3 A1 _0.7 N thick 3-5 microns. Then, the adhesion strength of the coating to the stainless substrate was determined by sclerometry. The criterion for high-quality coating is a critical normal force of at least 42 N, that is, this is the adhesion value of a Ti _t Al _1-t N coating deposited by physical vapor deposition (PVD).

 The test results are shown in table 4.

As can be seen from the results presented in table 4, only the coating composition, consisting of 70-80% Ti _t Al _1-t N and 20-30% Zr _y Al _1-y N, provides the necessary adhesion of the coating to the substrate and when leaving claimed limits the adhesion strength of the coating (adhesion) to the substrate is reduced.

 The rationale for the application of the claimed coating compositions to the external and internal surfaces of the mating parts.

To justify the tribological properties of the coatings of the claimed physicochemical composition, 10 pins with a diameter of 10 mm and 10 disks, for example, made of 12X18ShOT stainless steel, were made. The disk size is: diameter 50 mm, thickness 10 mm. The surface of the disks was coated with the claimed physicochemical composition, namely Ti _0.1 Al _0.9 N, and the pins were coated with 6 coatings of the following composition: TiN, Ti _0.8 Al _0.2 N, Ti _0.6 Al _{0 , 4} N, Ti _0.5 Al _0.5 N, Ti _0.4 Al _0.6 N, Ti _0.3 Al _0.7 N. Then the samples were installed on a friction machine, where the friction coefficient was measured. A criterion satisfying the ability of a friction pair is a friction coefficient μ of 0.2.

 The test results are presented in table 5.

Thus, as can be seen from table 5, when coating Ti _t Al _1-t N, where t = 0.8 - 0.9, on the outer surfaces of the parts with mating surfaces and coating Ti _x Al _1-x N, where x = 0.1 - 0.2, on the inner surface of the part with the mating surfaces of the coefficient of friction μ has a value equal to 0.3. However, this coefficient does not satisfy the required criterion.

To reduce the coefficient of friction of a friction pair in a coating intended for the outer surfaces of the mating parts, in addition according to the claimed technical solution, Zr _y Al _1-y N is introduced, where y = 0.2 - 0.3.

 To test the tribological properties of the coating of the claimed physicochemical composition, 10 pins with a diameter of 10 mm were made, for example, of stainless steel grade 12X18H10T.

The pins were coated with Ti _0.8 Al _0.2 N - 80%, Zr _y Al _1-y N - 20%, and the discs were coated with Ti _0.1 Al _0.9 N. Then, the samples were mounted on a friction machine and measured the coefficient of friction (μ). A criterion that satisfies the performance of a friction pair is a coefficient of friction μ of 0.2.

 The results of the measurements are presented in table 6.

 As can be seen from table 6, only the claimed composition of the coatings applied to the outer surface and the inner surface of the mating parts provides a minimum coefficient of friction equal to 0.2. When going beyond these limits, the coefficient of friction increases.

 An example of a specific implementation.

To determine the reliability of the work of a friction pair of parts with mating surfaces, a hollow cylinder was taken with an internal hole of diameter 60 ^+0.19 mm, made, for example, of stainless steel 12X18H10T and with a surface roughness of 0.04 μm. A rod made, for example, of stainless steel 12X18H10T, having an outer diameter of ^60-0.1 mm, was used as a rod.

 To coat the claimed composition on the mating surfaces of the parts, the Bulat-6 vacuum unit was used.

A rod and a cathode are installed in the chamber of the vacuum unit for coating the composition Ti _t Al _1-t N, where t = 0.8 - 0.9 and Zr _y Al _1-y N, where y = 0.2 - 0.3, and% mass ratio is equal to Ti _t Al _1-t N - 70-80%, Zr _y Al _1-y N - 20-30%, then the vacuum chamber of the Bulat-6 installation is pumped out to a residual pressure of 6 • 10 ^{- 3} mmHg Art. and the parts are heated to a temperature of 300 ^o C. Then, during the ion bombardment, nitrogen is admitted to a pressure of 5 • 10 ^-3 mm Hg. with the simultaneous inclusion of the cathode to obtain the coating of the claimed physico-chemical composition.

Thus, a coating of Ti _0.1 Al _0.9 N - 80% and Zr _0.2 Al _0.8 N - 20% with a thickness of 3-5 μm on the rod was applied. After coating, the product was removed from the camera installation "Bulat-6".

Then, a hollow cylinder is installed in the vacuum chamber of the Bulat-6 installation and pumped out to a residual pressure equal to 6 • 10 ^-3 mm Hg. After that, the parts are heated to a temperature of 300 ^o C in the process of ion bombardment, then nitrogen is puffed up to a partial pressure equal to 6 • 10 ^-3 mm Hg. with simultaneous coating of Ti _x Al _1-x N on the inner surface of the hollow cylinder, where x = 0.1 - 0.2.

Thus, a coating of Ti _0.1 Al _0.2 N with a thickness of 3-5 mm was applied to the inner surface of the hollow cylinder.

Test the friction pair was carried out at a temperature of 100 ^o C and an air humidity of 80%.

For testing, the rod was installed inside the hollow sleeve. Then the rod made 4-6 double strokes with a speed equal to 5 mm / min, and after that it was stopped for 24 hours. Thus, 20 cycles were carried out. The reliability criterion for the friction pair was the lack of delay in the movement of the rod, while the roughness of the coating was 30-50 nm, and the microhardness of the coating was H _μ = 2900 kg / mm ² .

 Despite the presence of aluminum in the coatings on both mating parts, adhesion of the interacting materials does not occur. The mating surfaces of the parts are well rubbed. The friction coefficient is wounded 0.1. All of the above factors indicate the reliability of the friction unit.

 Analysis of the materiality of the differences.

When analyzing the significance of differences among the known technical solutions, it was found that coatings of a given physicochemical composition were obtained, for example, Ti _0.4 A1 _0.6 N, Ti _0.5 Al _0.5 N, Ti _0.15 Al _0.85 N ( see Properties of Ti _x Al _x N cooting tools by the catthodic arc ion playtting method American Vacuum Society).

This article presents the facts of studying known coating compositions in order to increase the service life of a cutting tool made of stainless steel, consisting of 18% chromium, 10% nickel, the rest is iron. The coating composition for the inner surfaces of parts with mating surfaces Ti _x Al _1-x N, where x = 0.1 - 0.2, and the coating composition for the outer surfaces of parts with mating surfaces made of Ti _t Al _1-t N, where t = 0 , 8 - 0.9, and Zr _for Al _1-y N, where y = 0.2 - 0.3, and the% mass ratio is Ti _t Al _1-t N - 70-80%, Zi _y Al _{1- y} N 20-30%, was chosen experimentally and technical literature known to the authors is not described.

 Thus, the known technical solution neither for the purpose nor for the achieved result does not coincide with the claimed technical solution, therefore, meets the criterion of "significant differences".

 The use of the claimed technical solution for parts with mating surfaces has certain advantages. So, the service life of a friction pair is increased by 2 times. In addition, the use of the proposed technical solution ensures the reliability of the friction pair.

Sources of information
1. Symposium of the USSR State Committee on Science and Technology, House of Scientific and Technical Propaganda, Moscow, and Leibold-Hereus (Germany), ed. Dr. Detlev Repenning, p. 9, 1986

 2. "Powder metallurgy" 30, 1987, p. 5).

3. Properties of Ti _x Al _1-x N cooting tools by the catthodic arc ion playtting method American Vacuum Society. J. Vac Sci, Technol. A 10 (4) Jul / Aug 1992. American Vacuum Society.

Claims (2)

1. Wear-resistant coating of parts with mating surfaces, containing titanium nitride, characterized in that the coating of the inner surface of the part contains titanium nitride Ti _x Al _1-x N, where x = 0.1-0.2, while the coating of the outer surface details contains as titanium nitride Ti _t Al _1-t N, where t = 0.8-0.9, and also additionally contains Zr _y Al _1-y N, where y = 0.2-0.3. 2. The wear-resistant coating according to claim 1, characterized in that it contains coating components of the outer surface of the part in the following ratio: Ti _t Al _1-t N - 70-80%, Zr _y Al _1-y N - 20-30%.

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