CZ2002572A3 - Protective polyfunctional mixed coating based on light alloys and process for producing thereof - Google Patents

Abstract

A protective multi-functional composite coating on non-ferrous alloys (Al, Mg, Ti, Nb, Al-Ti, Al-Be, Ti-Nb), consisting of a strong, hard, porous oxide-ceramic layer in the form of a matrix, and a functional compounds introduced into the pores of the matrix. The functional compounds are selected from a series of metals (Ni, Cu, Co, Fe, Cr, Mo, Ti, Al, Sb, Ag, Zn, Cd, Pb, Sn, Bi, In, Ga) and/or refractory compounds (carbides, oxides, nitrides, borides and silicides of the metals of groups IVB-VTB of the periodic system of elements). The oxide-ceramic matrix layer is applied by the oxidation of the base by the method of plasma electrolytic oxidation, and has high adhesion to the base. By regulating the parameters of the oxidation process, the required porosity of the oxide layer is achieved. The functional compounds are introduced into the porous structure of the ceramic matrix using any of the following processes: chemical or electrochemical precipitation from solutions, chemical or physical precipitation from the gaseous phase, or the friction-mechanical method (rubbing on). After the introduction of the functional compounds, the composite coating is subjected to finishing treatment with the aim of laying bare the apexes of the ceramic layer capable of taking load. The strongly developed surface of the porous structure of the matrix layer, bonded to the functional compound, creates a new coating with high cohesion strength. The composite coating acquires a combination of increased strength, hardness, wear and corrosion resistance, along with a certain plasticity and resistance to contact dynamic loads and vibrations.

Description

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The protective composite coating on non-ferrous Al, Mg, Ti, Nb, Al-Ti, Al-Be, and Ti-Nb non-ferrous alloys consists of a solid, hard, porous oxide-ceramic layer in matrix form and a functional component introduced into the matrix pores. The functional component is selected from metals Ni, Cu, Co, Fe, Cr, Mo, Ti, Al, Sb, Ag, Zn, Cd, Pb, Sn, Bi, In, Ga, carbides, oxides, nitrides, borides and silicides of metals groups IVB to VIB of the Periodic Table of the Elements. The oxide-ceramic matrix layer is deposited by oxidation of the base by a plasma-electrolytic oxidation method and has high adhesion to the base. By controlling the oxidation process parameters, the desired porosity of the oxide layer is achieved. The functional compounds are introduced into the porous structure of the ceramic matrix using chemical or electrochemical precipitation from solutions, chemical or physical precipitation from the gas phase or friction mechanical process. After incorporation of the functional compounds, the composite coating is subjected to a final treatment to expose the load-bearing tips of the ceramic layer.

and alloys based

Protective multifunctional mixed coating for the method of its production

Technical field

The invention is applicable to various fields of engineering, electronics, medicine and other fields in which non-ferrous metals and their alloys are used. The invention also relates to technology for applying protective coatings to such metals and alloys, as well as to components and articles made therefrom.

BACKGROUND OF THE INVENTION

The use of reinforced ceramic coated non-ferrous alloy parts instead of traditional materials (ceramics, high-alloy steels and cast iron) makes it possible to greatly increase the durability and reliability of high-load and wear parts, reduce weight and improve unit dynamic parameters.

At present, a considerable number of hard ceramic coatings have been formed, but these have very significant drawbacks in their use under extreme conditions with insufficient or no lubrication. Such thin wear-resistant coatings such as TiN, TiCN often destroy the lubricating film due to insufficient wettability, leading to a higher degree of wear, the relatively thick ceramic layers being frictional to the sintered ceramic in terms of wear. Their main drawbacks are the high coefficient of friction, heating of the friction interface where there is a lack of lubricant, intense wear of the counter-body as a result of the micro-cutting effect, breaking and chipping of ceramic particles and their participation in accelerating abrasive wear. Extensive surface finishing operations with a roughness Ra of 0.04 to 0.06 µm only partially solve this problem.

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Recently, there have been numerous attempts to make universal hard extreme alloys on non-ferrous protective coatings capable of operating under conditions and yet have low coefficient of friction, high wear resistance and good resistance to aggressive media.

One way to form such coatings is to form a porous ceramic coating on the protected component into which different fillers are introduced into the pores.

A method (U.S. Patent No. 5,487,826 A) is known to form a composite layer of Al, Mg and Ti alloys consisting of a porous protective oxide layer with introduction of fluoropolymer particles into its pores.

It is also known (WO 97/05302) to form a porous oxide layer on Al, Mg and Ti alloys by introducing SiO ₂ particles into its pores using sol-gel technology.

It is also known (RU 2 073 752) to introduce silicone organic oligomers into an oxide layer formed on aluminum alloy parts with subsequent heat treatment at 300-500 ° C.

A drawback common to all the above-mentioned methods is the limitation of their applicability at the high temperatures that arise when operating under extreme component use conditions and the low indicators of thermal and electrical conductivity of the coatings.

The factors of triboelectrization and heat emission significantly influence the nature of wear and the formation of wear products in friction pairs. Therefore, an increase in the thermal and electrical conductivity of the composite coatings can be achieved when metallic or behaving components are used therein.

There is a known method (US Patent No. 5,645,896 A) to finish a rotor of a screw pump, comprising first applying a coarse tungsten carbide layer of 50 to 125 μη thickness and then a nickel and chromium layer of thickness 75 to 150 μη until the carbide layer is completely covered. Final polishing reduces the rotor dimensions to its desired dimensions and removes the protective top of the carbide layer that carries the main load when the rotor is in use.

In the described method, the rotor is made of steel, but the gas thermal dusting method can be used to apply coatings of substantially any mixture to any substrate, but it is difficult to form uniform coatings on components having a complex shape in this way. Coatings applied by gas thermal dusting do not bind firmly to the substrate. This defect is worse when the substrate is formed of non-ferrous alloys, as they rapidly dissipate heat and intensively form thin oxide films on them by the action of a plasma jet. Non-ferrous alloys also respond critically to the high temperature of the dusting process, since the surfaces of aluminum and magnesium can melt and overheating of the titanium alloys will reduce their fatigue resistance.

A method (U.S. Patent No. 5,364,522) is known to apply a multifunctional composite coating consisting of ceramic films enriched with borides, carbides, nitrides, oxynitrides, and silicides. In the first stage of the process, the hydroxide ceramic layer is applied electrochemically to the substrate, in the second stage the enrichment (infiltration) of the ceramic layer with refractory compounds takes place in a gas or steam stream at a temperature of 450 to 800 ° C.

Coatings made in this way are strong, wear resistant and resistant to high temperature corrosion, but use • · · · • ·

- 4 high temperatures in this technology make it impossible to apply such coatings to parts made of non-ferrous alloys.

There is a known method (WO 96/13625) of applying wear-resistant anti-friction coatings to aluminum and aluminum alloys. The aluminum substrate is first anodized in a 15% sulfuric acid solution. The soft metal layer, in particular indium, tin, gallium, or a combination thereof, is then applied to the porous anode-oxide surface. The thickness of the anodic oxide coating is 1 to 500 μια and the thickness of the metal layer is 10 to 100 μια. During this process, at least 80% of the anode metal pores should be filled with metal.

The main problem of the described process is the low mechanical strength and instability of the base anode-oxide coating.

Anode coatings having a thickness greater than 10 µm have a large number of pores that are largely hydrated (the water content of the coating exceeds 10%) and their composition also comprises 10 to 20% of the electrolyte anions incorporated into the coating structure. When heated to more than 120 ° C, the electrolyte components and water separate from the coating structure, leading to cracks and lumps in the anode-oxide layer and impair its protective properties. The anode-oxide layers mainly consist of amorphous oxide phases and hence their strength and microhardness are not high.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a composite coating for non-ferrous alloy parts having good wear resistance and low coefficient of friction over the life of the component, resistance to aggressive media and the ability to withstand dynamic contact loads and vibrations.

A second object of the present invention is to provide a composite coating for non-ferrous alloy parts that has high resistance to resistance to corrosion. ·· ·· ····

- 5 wear and scratch resistance, erosion and abrasion resistance at high temperatures, as well as corrosion resistance.

A third object of the present invention is to provide an environmentally safe and comparatively inexpensive technology for applying composite coatings to non-ferrous alloys that can be used in mass production.

These and some other objects are solved by the present invention by providing a coating having the form of a porous oxido-ceramic coating formed by oxidation of a surface layer of a material that is protected by a plasma-electrolytic oxidation process into which pores such as Ni, Cu, Co, Fe are introduced. , Cr, Mo, Ti, Al, Sb, Ag, Zn, Cd, Pb, Sn, Bi, In, Ga and mixtures thereof or carbides, oxides, nitrides, borides and silicides of metals of Groups IVB to VIB of Mendeleev's Periodic System and their mixtures.

The formation of porous oxido-ceramic coatings on non-ferrous alloys by the plasma-electrolytic oxidation method was proposed by the inventor in the earlier international application PCT / RU97 / 00408 (publication WO 99/31303).

The adhesion of these coatings to the base is 5 to 10 times stronger than that of gas-thermally dusted coatings and their strength and microhardness are 2 to 5 times greater than those of the anodic oxide layers.

The oxidation takes place in environmentally harmless weakly alkaline aqueous electrolytes at a temperature of 15 to 55 ° C. The components are supplied with a pulse voltage of 100 to 1000 V (amplitude value).

The frequency of successive pulses is 50 to 3000 Hz. The current density is 2 to 200 A / dm ² .

· 4 4 4 4 4 4 4 4 444 44 44 44 4 4 4

A fine crystalline oxide layer with a microhardness of 300 to 2000 Hv, depending on the composition of the aluminum base, is formed on the surfaces of non-ferrous alloy parts by the effect of plasmachemical reactions. The layer thickness may be from 1 to 600 µm.

By varying the electrolysis regimes and the electrolyte composition, significant changes can be made in the physico-mechanical parameters of the oxide-ceramic coatings, and in particular in the size of their open porosity, which can vary from 5 to 35%.

As a result of the studies, the discovery that if the above metals or carbides, oxides, nitrides, borides and silicides of metals of Groups IVB to VIB of the Periodic System and mixtures thereof were introduced into the pores of such a coating, the coating would acquire unique properties plasticity, high wear and scratch resistance, high corrosion resistance and resistance to mechanical contact loads and vibrations.

The pore size varies from a few tens of nm (nanometers) to a few pm (microns) in diameter. Pore sizes larger than 1 µm comprise more than 90% of the volume of all pores. Most of the mass of functional substances is introduced into these pores.

The porous structure of the oxide-ceramic layer serves as a matrix to form a multifunctional composite coating. It should be noted that the porosity of the coating varies with the depth of the coating. It is at its maximum n surface, but is less than two to six times as far as the parent metal. The concentration of functional compounds introduced into the pores corresponds to these parameters - it is at its maximum in the surface layer and decreases exponentially with increasing coating depth. Oxide-ceramic coatings with an open porosity of 10 to 20% form an ideal matrix for forming composite coatings by filling this matrix with compounds having specific

properties and fulfilling specific functions (anti-friction, thermal conductivity, anti-corrosive etc.).

The microhardness of the oxido-ceramic coating, on the other hand, has maximum values close to the parent metal and still decreases towards the outer surface of the coating (by 20-30%).

The firmly developed surface of the porous matrix layer structure provides excellent adhesion of the functional compounds to the oxide coating. This gives the composite coating its high cohesion strength.

The first group of functional compounds introduced into the pores of the oxide layer consists of the soft metals Ni, Cu, Co, Fe, Cr, Mo, Ti, Al, Sb, Ag, Zn, Cd, Pb, Sn, Bi, In, Ga and mixtures thereof .

The metal exerts a plasticizing effect on the composite coating. The specific nature of this coating is given by its deformation behavior under thermomechanical loading. The two-phase ceramic-metal structure provides a five-fold increase in shock viscosity compared to pure ceramics.

Such coatings can also be used as antifriction coatings. After the finishing treatment, the sectors of the oxide-ceramic layer are exposed. These firmer sectors on the frictional surface assume the main load and thus increase the surface bearing capacity.

Furthermore, the softer surface sectors as they wear out create micro-recesses and grooves that serve as lubricant reservoirs and their presence changes the lubrication mode at frictional contact, facilitates removal of the wear products and thus improves the working ability of the surface.

Taking into account the friction mode in the unit, the presence of lubricant and the condition of the contact surfaces, composite coatings can be formed that optimally match the specific conditions of use with

- 8 optimal porosity and optimal composition of functional compounds in the pores of the composite coating.

The second group of functional compounds that are introduced into the pores of the oxide layer consists of refractory compounds of metals of Groups IVB to VIB in Mendeleyev's periodic system of elements: carbides, oxides, nitrides, borides, and silicides.

The use of these compounds separately or together with metals as functional materials introduced into the ceramic coating matrix imparts to the composite coating such properties as high hardness and strength, high temperature resistance and exceptionally high abrasion resistance. Such compounds, located in the pores, cure the composite coating and alter its thermophysical and mechanical properties.

All of the above functional compounds are applied to the porous ceramic matrix layer by known methods of electrolytic and chemical precipitation from aqueous or organic solutions, including the use of ultra-dispersible powders, chemical or physical precipitation from the gas or vapor phase, or friction mechanical method (spreading) using powders. , sticks, brushes, etc.

Using these methods, the functional compounds are introduced into the pores of the oxide-ceramic matrix coating to a depth of 1 to 150 μπι, depending on the depth of the oxide coating itself and the pore volume therein.

The working surface is subjected to machining (polishing, lapping, fine grinding, honing, superfinishing) until the parts have the required dimensions and surface roughness or until the tops of the oxide-ceramic coating are exposed (exposed). This machining allows to remove excessive layers of functional compounds and distribute the remaining part evenly over the surface.

h · ···· ·· · ·

Machining also means that running-in of friction surfaces is not required.

Overview of the drawings

The attached drawings show the following:

Fig. 1 is a cross-sectional view of a composite-coated sample applied thereto, showing the bonding functional material 1, pores in the oxide matrix coating 2, the oxide-ceramic matrix coating 3, the intermediate layer 4 between the parent metal and the oxide coating and the base metal 5.

Fig. 2 shows a cross-section of the sample after the final surface treatment (polishing) of the composite coating, showing the binding functional material 1, pores in the oxide matrix coating 2, the oxidoceramic matrix coating, the transition layer 4 between the parent metal and the oxide coating, parent metal 5 and projections 6 of the oxide coating on the work surface.

DETAILED DESCRIPTION OF THE INVENTION

The following examples specifically illustrate the claimed invention, but it is to be understood that the invention is not limited to those specific ingredients set forth in these examples.

Example 1 (comparative)

The sample of alloy D16 (AlCu ₄ Mg ₂ ) is in the form of a ring with dimensions D = 40 mm, d = 16 mm and h = 12 mm. The external cylindrical surface is subjected to plasma electrolytic oxidation for 120 min in a fostate-silicate electrolyte (pH 11) at 30 ° C. The mode is anode-cathode, current density is 20 A / dm ² , magnitude (amplitude) of final voltage: anode 600 V, cathode 190 V. The depth of the oxide-ceramic coating is 120 gm, microhardness is 1800 Hv, open porosity is 20%.

Example 2

The sample of alloy D16 (AlCu ₄ Mg ₂ ) is subjected to the same treatment as the sample in Example 1 and has the following parameters: oxide layer depth of 120 μη, microhardness 1800 Hv, open porosity of 20%.

The sample was subjected to chemical nickel plating and then polishing. The depth of nickel penetration after polishing is about 10 μπι. The nickel concentration is at its maximum in the layer near the surface and decreases exponentially as the depth of the coating increases.

Example 3

A sample of the AK4-2 alloy (AlCu ₂ , Mg ₂ Fe Ni) is subjected to plasmoelectrolytic oxidation for 90 minutes in phosphate-silicate electrolyte (pH 11) at 30 ° C. mode is anode-cathode, current density is 15 A / dm ² , final voltage: anode 550 V, cathode 120 V. Depth of oxide-ceramic coating is 70 μπι, microhardness is 1550 Hv, open porosity is 16%.

A composite layer consisting of 20% Cr and 80% Cr ₂ C ₂ is applied to the sample by a chemical precipitation method from the gas phase. The sample was heated to 300 ° C during precipitation. The sample was then polished. The penetration depth of the functional compound CrCr ₃ C ₂ into the porous structure was about 7 µπι.

Example 4

A sample of the VT6 alloy (TiAl ₆ V ₄ ) was oxidized in aluminum sulfate as the electrolyte (pH 9) for 20 minutes at 20 ° C. Mode: anode, current density 50 A / dm ² , final anode voltage 300 V. Oxide coating depth 15 μπι, microhardness 690 Hv, open porosity 12%.

The nickel layer was deposited on the sample by a method of chemical precipitation from the gas phase. During precipitation the sample was • · «·

- 11 heated to 200 ° C. Then the cylindrical surface of the sample was polished. The penetration depth of the nickel compound into the porous structure was 3 μια.

Example 5

A sample of the VMD12 alloy (MgZn ₆ MnCu) was oxidized in aluminum fluoride as an electrolyte (pH 12) for 40 minutes at 20 ° C. Mode: anode-cathode, current density 8A / dm ² , size of final voltage: anode 350 V, cathode 130 V. Depth of oxide-ceramic coating 30 μη, microhardness 750 Hv, open porosity 25%.

The nickel composite layer was applied to the sample by a chemical precipitation method from the gas phase. During precipitation, the sample was heated to 200 ° C. Then the cylindrical surface of the sample was polished. The penetration depth of the nickel compound into the porous layer structure was 10 μη.

Example 6

A localloy type ABM-3 (AlBe ₆ oMg2) sample was oxidized in phosphate-silicate electrolyte (pH 11) for 120 minutes at 30 ° C. Anode-cathode mode, current density 15 A / dm ² , terminal voltage: 480 V anode, 110 V cathode. Oxidic-ceramic coating depth 100 μπι, microhardness 790 Hv, open porosity 18%.

The nickel composite layer was applied to the sample by a chemical precipitation method from the gas phase. During precipitation, the sample was heated to 200 ° C. Then the cylindrical surface of the sample was polished. The penetration depth of the nickel compound into the porous structure of the oxide layer was 8 μια.

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Tests of friction pairs, made up of components with different types of coating and hardened steel counterparts, were carried out on a universal friction machine.

A ring-cylinder arrangement with intersecting axes for point contact was selected. The fastened steel sample ShKhl5, hardness HRC3 5860, was pressed into the moving sample (ring) on which the coating to be examined was formed.

The tests were carried out in a friction friction mode in which several drops of spindle oil were applied to the coated sample prior to testing. The slip speed was 2 m / s, the normal contact load was 75 N. The test lasted 60 s. Ten identical tests were performed with each ring. The mean values for the parameters were calculated from the results of these tests.

Studies have also served to evaluate friction parameters such as wear resistance, friction coefficient and load capacity. The wear resistance was assessed from wear and weight by comparing the dimensions of the locations on the steel sample and the weight loss of the coated sample.

The results of the technical friction tests are given in Table 1.

The test results show the effectiveness of using composite coatings on a variety of substrates as compared to a conventional oxide-ceramic coating on an aluminum alloy. The coefficient of friction is slightly more than half, the wear of the counter-body decreases

2 to 5 times, and wear of the ring coating itself up to 10 times.

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- 13 Table 1

Number tested sample (Number example) Wear sample with coating [mg] Wear area on steel counterpart [mm ² ] Coefficient friction 1 1, 96 2.83 0, 439 2 0, 25 1.18 0, 202 3 0.16 1.46 0.232 4 0, 63 0, 74 0, 185 5 0, 75 0, 55 0.171 6 0, 19 1,23 0, 225

Industrial applicability

Because the proposed composite coating has such exceptional properties as high strength and hardness combined with some plasticity, excellent wear and scratch resistance, and high corrosion and vibration resistance, we have the opportunity to significantly expand the use of non-ferrous metal components.

It also increases the durability and reliability of components operating under extreme conditions with various forms of wear (abrasive wear at high temperatures and aggressive media, dynamic contact loads and vibrations).

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The wide range of metals and ceramic compounds used as functional materials introduced into the porous ceramic matrix makes it possible to select the optimal parameters of the composite coatings for the actual conditions of use.

The proposed process for the production of protective coatings is distinguished in that it is environmentally friendly and requires low costs and is suitable for use on an industrial scale.

Claims (13)

PATENT CLAIMS (MODIFIED) A protective composite coating applied to non-ferrous metals, their alloys and intermetallic compounds, as well as components made thereof, wherein the composite coating is in the form of a first porous oxide-ceramic matrix coating formed by plasma by electrolytic oxidation of the surface layer of the material being protected and a second a coating formed by introducing at least one functional component selected from the group consisting of Ni, Cu, Co, Fe, Cr, Mo, Ti, Al, Sb, Ag, Zn, Cd, Pb, Sn, Bi, In, Ga and mixtures thereof, carbides, the oxides, nitrides, borides and silicides of metals of Groups IVB to VIB of the Mendeleyev Periodic Table of the Elements, and mixtures thereof into the pores of the first matrix coating, characterized in that the surface portions of the first matrix coating project from below. Protective composite coating according to claim 1, characterized in that it is applied to the non-ferrous metals Al, Mg, Ti, Nb and their alloys as well as the compounds AlTi, Ti-Nb and Al-Be. Protective composite coating according to claim 1 or 2, characterized in that the oxido-ceramic matrix coating has an open porosity of 5 to 35%, porosity decreasing along the coating thickness inwards from the outer layer, wherein the microhardness of the oxido-ceramic coating is 300 to 2000 HV and increases through the thickness inwards from the outer layer, and the total thickness of the oxide-ceramic layer is 1 to 600 μπι, preferably 3 to 150 μη. 4 · 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 44 ·· 4444 -> 3 - Λ <» The protective composite coating according to claim 3, characterized in that the oxide-ceramic matrix coating has an open porosity of 10 to 12%. Protective composite coating according to claims 1 to 4, characterized in that the functional components are introduced into the pores of the oxide-ceramic matrix coating to a depth of 1 to 150 µm, preferably 2 to 100 µη. 6. A method of applying a protective composite coating to non-ferrous metals, their alloys and intermetallic compounds, as well as to compounds made thereof, comprising the following phases: a) plasma-electrolytic oxidation of the surface layer of the material to be protected, wherein the operating voltage and current density are controlled so as to produce a first oxide-ceramic matrix coating with a predetermined porosity, b) introducing into the pores of the first oxido-ceramic matrix coating formed in phase a) at least one functional compound selected from the group consisting of Ni, Cu, Co, Fe, Cr, Mo, Ti, Al, Sb, Ag, Zn, Cd, Pb , Sn, Bi, In, Ga and mixtures thereof, carbides, oxides, nitrides, borides and silicides of the metals of Groups IVB to VIB of Mendeleev's Periodic System of Elements, and mixtures thereof, so as to form a second coating, and c) finishing the surface of the composite coating so that the surface portions of the first matrix coating penetrate from below the second coating. 99 * ·· * 99 99 9 9 9 9 9 9 9 9 9 9 9 9 9 9 99 99 Ί. Application method according to claim 6, characterized in that the plasma electrolytic oxidation takes place at a voltage of 100 to 1000 V, a current density of 2 to 200 A / dm ² . Coating method according to claim 6 or 7, characterized in that the plasma electrolytic oxidation takes place at a temperature of 10 to 55 ° C. Application method according to claims 6 to 8, characterized in that the introduction of the functional compounds into the pores of the first matrix coating is carried out by electrochemical precipitation from aqueous or organic solutions including the use of ultradisperse powders. Coating method according to claims 6 to 8, characterized in that the introduction of the functional components into the pores of the first matrix coating is carried out by chemical precipitation from an aqueous or organic solution. Deposition method according to Claims 6 to 8, characterized in that the introduction of the functional components into the pores of the first matrix coating is carried out by chemical precipitation from the gas phase. Application method according to Claims 6 to 8, characterized in that the introduction of the functional components into the pores of the first 9 • · ·· «t · 9 9 9 9 9 9 9 9 9 9 The rf matrix coating is performed using physical precipitation methods. Application method according to claims 6 to 8, characterized in that the introduction of the functional components into the pores of the first matrix coating is carried out by means of frictional mechanical rubbing, using powders, rods or brushes. Coating method according to claims 6 to 13, characterized in that the finishing of the composite coating is selected from the following operations: polishing, fine grinding, lapping, honing and superfinishing.