KR20020042642A - Light alloy-based composite protective multifunction coating - 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

Multifunctional coating for light alloy composite material protection {LIGHT ALLOY-BASED COMPOSITE PROTECTIVE MULTIFUNCTION COATING}

By using non-ferrous alloy components coated with hardened ceramics instead of components of conventional materials (ceramic, high alloyed steels and cast iron), significant increases in durability and dependence of heavily loaded and rapidly worn components, reduced weight and improved unit dynamics To make it possible.

Currently coating a significant amount of hard ceramics, but they are quite insufficient for use in extreme conditions with insufficient lubrication or no lubrication at all. Thin waterproof coatings such as TiN, TiCN, etc., due to inadequate wettability, often destroy the lubricating film, increasing wear. Due to the nature of this friction wear, relatively thick ceramic coatings are close to sintered ceramics. These are major defects with high coefficients of friction and heat generation at the friction interface, where lubrication is a consequence of the micro-cutting effects of ceramic particles, the consequences of acceleration of separation, micro-chipping and frictional wear. Insufficient and intensive wear of the object. Intensive surface finishing alone solves this problem by bringing the roughness to Ra 0.04-0.06 μm.

Recently, there have been increasing attempts to make general protective coatings for non-ferrous alloy components that can operate in very rough conditions and still have low friction coefficients, high resistance to abrasion and good resistance to active media.

One method of such a coating is to form a coating on the protective component of a porous ceramic coating with pores inserted with many fillers.

Therefore, a process (US Pat. No. 5,487,826A) of forming a composite material layer composed of a porous protective oxide layer in which fluorinated polymer particles are inserted into a cavity is known on Al, Mg and Ti alloys.

A process of forming a porous oxide film by inserting SiO ₂ particles into an air on Al, Mg, and Ti alloys using a sol-gel technique (WO 97/05302) is known.

Also known is a process (RU 2073752) for inserting a silicon-organic oligomer into an oxide layer formed on an aluminum alloy component by continuous heat treatment at 300-500 ° C.

Common drawbacks to all of the above processes are the application limits at high temperatures resulting from operating under extreme conditions when using the components, and the low thermal and electrical conductivity of the coating.

Triboelectric and heat dissipation factors have a significant impact on wear characteristics and formation of wear products in friction pairs. Thus, the thermal and electrical conductivity of the composite material coating can be increased by using metal components or components such as metals in them.

A gas-thermal dusting-on process was applied to the surface to initially form a coarse tungsten carbide layer up to 50-125 μm thick, then 75-150 μm thick until it completely covered the carbide layer. A process for surface treatment of a screw pump rotor involving the formation of a nickel-chromium layer (US Pat. No. 5,645,896A) is known. The rotor is reduced to the required size by final polishing, and the use of the rotor exposes the protective apex of the carbide layer under main load.

In the above process, the rotor is made of steel. However, a gaseous dusting process can be used to apply a coating of virtually any composition to any backing. However, it is difficult to form uniform coatings on complex shaped components by this process. In addition, the coating applied with the gas heat dusting process does not adhere to the substrate sufficiently firmly. Since nonferrous alloys dissipate heat rapidly and form thin oxide films intensively under the influence of plasma jets, these defects become worse when they form a substrate. In addition, aluminum and magnesium alloy surfaces can melt, and overheating of titanium alloys reduces fatigue resistance, so non-ferrous alloys are critically reacted in hot sparging processes.

A process for applying a multifunctional composite coating consisting of ceramic films rich in boride, carbide, nitride, oxynitride and silicides (US Pat. No. 5,364,522A) Known. In the first stage of the process, the hydrogen oxide ceramic layer is electrochemically applied to the backing, and in the second stage, the rich (soaked) ceramic layer with the refractory compound occurs in a gas stream or vapor stream at a temperature of 450-800 ° C. do.

Coatings made in this process are strong, abrasion resistant and resistant to high temperature corrosion. However, using high temperatures in this technique makes it impossible to apply such coatings to compositions made of non-ferrous alloys.

Processes for applying abrasion resistant non-friction coatings to aluminum and aluminum alloys (WO 91/13625) are known. The aluminum backing is first anodized in 15% sulfuric acid solution. Next, a soft metal layer is applied to the porous anodic oxidation surface, i.e. indium, tin, gallium and their compounds. The thickness of the anodizing coating is 1-500 μm and the thickness of the metal layer is 10-100 μm. At least 80% of the pores of the anode metal must be filled with metal during this process.

The main problem with the above process is the low mechanical strength and instability of the anodized coating of the substrate.

Cathode coatings having a thickness of 10 μm or more have a large number of pores, and they are hydrated to a significant extent (more than 10% moisture content of the coating), and these compositions also contain 10-20% of electrolyte anions formed in the coating structure. . When heated to 120 ° C. or higher, the electrolyte component and moisture are separated from the coating structure, which causes cracking and chipping of the anodic oxide layer and adversely affects the protective properties. In addition, since the anodic oxide layer mainly consists of an amorphous phase of an oxide, strength and fine hardness are not high.

The present invention can be used in a variety of fields such as engineering, electronics, medical, and other non-ferrous metals and their alloys, and more specifically, a technique for applying a protective coating to metals and alloys, components and products prepared therefrom. It is about.

1 is a cross-sectional view of a specimen coated with a composite material and having the same.

2 is a cross-sectional view of a specimen in which finishing (polishing) of the composite material coating is completed.

<Explanation of symbols for main parts of the drawings>

1. Functional material for bonding

2. Public in oxide matrix coating

3. Oxidized Ceramic Matrix Coating

4. Transition layer between base metal and oxide coating

5. Base metal

6. The protrusion of the oxide coating on the working surface

One feature of the present invention relates to the development of composite coatings for non-ferrous alloy components with good abrasion resistance, low coefficient of friction of components during working life, resistance to active media, and the ability to withstand dynamic contact loads and vibrations.

A second aspect of the present invention relates to the development of a compound coating for a non-ferrous alloy component having high abrasion resistance and scratch resistance, corrosion abrasion resistance and operating resistance and corrosion resistance of high temperature friction media.

A third aspect of the invention relates to the development of a biologically stable and relatively inexpensive technique for coating compounds on nonferrous metals that can be used in serial production.

Other features are made in accordance with the present invention by forming a coating in the form of a porous oxide ceramic formed by oxidation of the surface layer of the material protected by plasma electrolytic oxidation. Groups 4B to 6B of Ni, Cu, Co, Fe, Cr, Mo, Ti, Al, Sb, Ag, Zn, Cd, Pb, Sn, Bi, In, Ga and mixtures thereof or Mendelev periodic table Metals such as carbides, oxides, nitrides, borides, silicides and mixtures thereof are inserted.

The inventor of the present invention proposed the formation of a porous oxide ceramic coating on a non-ferrous alloy according to the plasma electrolyte oxidation method in the previous international application PCT / RU97 / 00408 (WO 99/31303).

The adhesion of this coating to the substrate is 5-10 times stronger than the coating adhesion with gas heat dusting, and the strength and fine hardness are 2-5 times larger than the anodization layer.

Oxidation takes place in a weakly alkaline aqueous electrolyte with no biohazard at temperatures of 15-55 ° C. Supply a pulse voltage of 100-1000 V (magnitude) to the component.

The continuous pulse frequency is 50-3000 Hz. The current density is 2-200 A / dm ² .

A microcrystalline oxide layer having a fine hardness of 300-2000 Hv depending on the composition of the alloy substrate is formed on the surface of the nonferrous alloy component under the influence of the plasma chemistry. The thickness of the layer is 1-600 μm.

By changing the electrolytic system and electrolytic composition, significant changes in the physico-mechanical properties of the ceramic oxide layer can occur, in particular significant changes in the size of the open cavities, which can vary from 5-35%.

As a result, when carbides, oxides, nitrides, borides, silicides, and mixtures thereof of the metals described above or metals of Groups 4B to 6B of the Periodic Table are inserted into the pores of such coatings, the coatings It has unique characteristics in strength and hardness along with high resistance, high corrosion resistance and resistance to mechanical contact load and vibration.

The size of the pores varies in diameter from tens of nm to several microns. The pores of 1 μm or more occupy more than 90% of the total pore volume. This mass inserts most of the mass of functional compounds.

The porous structure of the oxide ceramic layer acts as a matrix for forming a multifunctional composite material coating. Note that the porosity of the coating varies with the depth of the coating. The porosity is maximum at the surface, and as it approaches the base metal, the porosity decreases to the left power of 2-6. The concentration of functional compound inserted into the cavity coincides with this property. The concentration is maximum at the subsurface layer and decreases exponentially with increasing coating depth. Oxidized ceramic coatings with 10-20% open porosity fill the matrix with compounds with specific properties and perform specific functions (non-friction, thermal conductivity, non-corrosion, etc.) to form an ideal matrix for producing composite coatings .

On the other hand, the fine hardness of the oxidized ceramic coating has a maximum near the base metal and gradually decreases toward the outer surface of the coating (about 20-30%).

The porous structure surface of the matrix layer researched and developed provides excellent adhesion of the functional compound to the oxide coating. Composite coatings thereby have a high adhesive strength.

The first group of functional composite materials inserted into the pores of the oxide layer are soft metals Ni, Cu, Co, Fe, Cr, Mo, Ti, Al, Sb, Ag, Zn, Cd, Pb, Sn, Bi, In, Ga And mixtures thereof.

Metals exhibit a plastic effect on the composite material coating. The specific nature of these coatings is due to the deformation behavior at thermomechanical loads. Two-phase ceramic-metal structures have a five-fold increase in impact viscosity as opposed to pure ceramics.

Such coatings can also be used as non-frictional coatings. After the treatment, the portion of the ceramic oxide layer is exposed. The stronger part on this frictional surface is subjected to the main load, thereby increasing the resistance of the surface.

In addition, with wear, the soft parts of the surface form fine recesses and grooves, which act as friction reservoirs, alter the friction system during frictional contact, and facilitate the removal of wear products, thus allowing the surface to work. To improve.

Considering the friction scheme in the unit, the lubrication, the condition of the contact surface and the composite coating can be formed to optimally match the particular conditions of use with the optimum porosity and optimum composition of the functional compound in the voids of the composite coating.

The second group of functional compounds inserted into the pores of the oxide layer consists of refractory compounds of Group 4B to Group 6B metals, namely carbides, oxides, nitrides and silicides in Mendelev's Periodic Table of Elements.

When using such compounds separately or in combination with a metal as a functional material embedded in the ceramic matrix of the coating, the composite coating has properties such as high hardness, high strength, resistance to high temperatures and exceptionally high wear resistance. These compounds, located in the vacancy, cure the composite coating and change the thermophysical and mechanical properties.

The aforementioned functional compounds may be prepared from superdisperse powders, chemical or physical precipitates from gaseous or vapor phases, or from aqueous or organic solutions, including using frictional mechanical (frictional) methods using powders, rods, brushes, and the like. It is applied to the porous ceramic matrix layer by known methods of electrolytic or chemical precipitates.

Using this method, the functional compound is inserted into the pores of the oxide ceramic matrix coating to a depth of 1-150 μm depending on the depth of the oxide coating itself and the void volume therein.

Mechanical finishing operations (gloss, lapping, fine grinding, honing and precision finishing) until the working surface is of the size and surface roughness required by the component or the apex of the oxide ceramic coating is exposed (peeled). Do it. This mechanical treatment removes the transient layer of functional compound and evenly distributes the remainder on the surface. Machining also means that there is no need to tame the friction surface.

The following examples are given according to the specific examples of the invention claimed by right. However, it is not intended that the present invention be limited to the specific components contemplated in the given examples.

First Embodiment (Comparative)

Specimens of alloy D16 (AlCu ₄ Mg ₂ ) are in the form of rings with dimensions D = 40 mm, d = 16 mm and h = 12 mm. The outer cylindrical surface is plasma electrolytically oxidized for 120 minutes at 30 ° C phosphate silicate electrode (pH 11). The scheme is anode-cathode, current density is 20A / dm ² , final voltage magnitude is 600V for anode and 190V for cathode. The oxide ceramic coating has a depth of 120 μm, a fine hardness of 1800 Hv, and an open porosity of 20%.

Second embodiment

The specimen of alloy D16 (AlCu ₄ Mg ₂ ) is subjected to the same treatment as in the first embodiment, and has an oxide coating having a depth of 120 µm, a fine hardness of 1800 Hv, and an open porosity of 20%.

The specimen is polished by chemical nickel plating. After polishing, the penetration depth of nickel is about 10 μm. The concentration of nickel is maximum in the surface adjacent layer and decreases exponentially as the depth of the coating increases.

Third embodiment

Specimens of alloy AK4-2 (AlCu ₂ , Mg ₂ Fe Ni) were plasma electrolytically oxidized for 90 minutes in a phosphate silicate electrolyte (pH 11) at 30 ° C. The scheme is anode-cathode, current density is 15A / dm ² , final voltage magnitude is 550V for anode and 120V for cathode. The oxide ceramic coating has a depth of 70 μm, a fine hardness of 1550 Hv, and an open porosity of 16%.

The specimen is coated with a composite material layer consisting of 20% Cr and 80% Cr ₃ C ₂ by chemical precipitation from the gas phase. The specimen is heated to 300 ° C. during precipitation, and then the specimen is polished. The penetration depth of the functional compound Cr-Cr ₃ C ₂ into the porous structure is about 7 μm.

Fourth embodiment

Specimens of alloy VT6 (TiAl ₆ V ₄ ) are oxidized for 20 minutes in 20 ° C. aluminate sulfate electrolyte (pH 9). The scheme is anode, the current density is 50A / dm ² , and the final anode voltage is 300V. The depth of the oxide coating is 15 μm, the fine hardness is 690 Hv, and the open porosity is 12%.

A nickel layer is formed on the specimen by chemical precipitation from the gas phase. The specimen is heated to 200 ° C. during the precipitation process. Thereafter, the cylindrical surface of the specimen is polished. The penetration depth of the nickel compound into the porous structure is 3 μm.

Fifth Embodiment

Specimens of alloy VMD12 (MgZn ₆ MnCu) are oxidized for 40 minutes in a fluorinated aluminate electrolyte (pH 12) at 20 ° C. The scheme is anode-cathode, current density is 8A / dm ² , final voltage magnitude is 350V for anode and 130V for cathode. The oxide ceramic coating has a depth of 30 μm, a fine hardness of 750 Hv, and an open porosity of 25%.

A nickel composite material layer is formed on the specimen by chemical precipitation from the gas phase. During precipitation, the specimen is heated to 200 ° C. Thereafter, the cylindrical surface of the specimen is polished. The penetration depth into the porous structure of the layer of nickel compound is 10 μm.

Sixth embodiment

Specimen of “localloy” type alloy ABM-3 (AlBe ₆ 0Mg ₂ ) was oxidized in a phosphate silicate electrolyte (pH 11) at 30 ° C. for 120 minutes. The scheme is anode-cathode, current density is 15A / dm ² , final voltage magnitude is 480V for anode and 110V for cathode. The oxide ceramic coating has a depth of 100 μm, a fine hardness of 790 Hv, and an open porosity of 18%.

A nickel composite material layer is formed on the specimen by chemical precipitation from the gas phase. The specimen is heated to 200 ° C. during the precipitation process. Thereafter, the cylindrical surface of the specimen is polished. The penetration depth of the nickel compound into the porous structure oxide layer is 8 mu m.

Testing of friction pairs formed from components with different types of coatings of hardened metals and corresponding specimens is done on ordinary friction machines.

Choose a ring cylinder arrangement with intersecting axes for contact contact. Fixed specimens of ShKh15 steel with a hardness of HRC ₃ 58-60 are pressed onto a moving specimen (ring) with a coating for the study application.

The test is carried out in a boundary friction system, and a number of spindle oil droplets are applied to the coated specimen before testing. The slip speed is 2 m / sec at 75 N, the normal load at specimen contact. The test is run for 60 seconds. Ten identical tests are performed on each ring. From these test results, the average value of the properties is calculated.

In addition, studies are conducted to evaluate friction characteristics such as wear resistance, friction coefficient and load capacity. Friction resistance is estimated from wear weight and size by comparing the spot size on the steel specimen and the mass loss of the coated specimen.

The technical friction test results are given in Table 1 below.

The test results show the efficiency of using composite coatings on various backings compared to conventional oxide-ceramic layers on aluminum alloys. Thus, the coefficient of friction is slightly over half, the wear of the object decreases to the left power of 2-5, and the wear of the ring coating itself decreases to the left power of 10.

The proposed composite coating has unique properties such as high strength and hardness, with specific plasticity, exceptional resistance to abrasion and scratches, and high resistance to corrosion and vibration, so there is an opportunity to apply a wide range of nonferrous metal components.

The durability and dependence of components operating under extreme conditions under the simultaneous influence of different forms of wear (high temperature, active media, dynamic contact loads and frictional wear in vibrations) also increases.

The wide range of metals and refractory compounds used as functional materials embedded in porous ceramic matrices allows the selection of optimal properties of composite coatings in practical use conditions.

The proposed process for producing protective coatings is excellent in terms of biohazards and inexpensiveness and is suitable on an industrial scale in use.

Claims (12)

As a protective composite coating applied to nonferrous metals, alloys and intermetallic compounds thereof, and components prepared therefrom, Porous oxide ceramic matrix coating form, formed by oxidation of the material surface layer protected by plasma electrolytic oxidation method, Ni, Cu, Co, Fe, Cr, Mo, Ti, Al, Sb, Ag, Zn, Cd, Pb, Carbides, oxides, nitrides, borides, and silicides of Sn, Bi, In, Ga, and mixtures thereof, or metals of Groups 4B to 6B of the Mendelev Periodic Table And at least one of the functional compounds selected from compounds such as mixtures thereof is inserted. In claim 1, A composite material coating characterized by being applied to non-ferrous metals of Al, Mg, Ti, Nb and their alloys, and to Al-Ti, Ti-Nb and Al-Be compounds. In claim 1, The ceramic oxide matrix coating has an open porosity of 5-35%, preferably an open porosity of 10-12%, in which the porosity in the coating thickness in the inward direction from the outer layer is reduced, The fine hardness is 300-2000 HV and increases in thickness from the outer layer to the inside, and the total thickness of the ceramic oxide layer is 1-600 μm, preferably 3-150 μm. In claim 3, A composite material coating, wherein said functional compound is inserted into a cavity of said oxide ceramic matrix coating to a depth of 1-150 μm, preferably 2-100 μm. As a method for applying a protective composite coating to nonferrous metals, alloys and intermetallic compounds and components made therefrom, (a) plasma electrooxidizing the surface layer of the material to be protected, (b) Ni, Cu, Co, Fe, Cr, Mo, Ti, Al, Sb, Ag, Zn, Cd, Pb, Sn, Bi, In, Ga and mixtures thereof, and Groups 4B to 6B of Mendelev Periodic Table At least one of the functional compounds selected from compounds such as carbides, oxides, nitrides, borides and silicides of group metals and mixtures thereof is inserted into the pores of the oxide layer produced in step (a), and (c) mechanically finishing the surface of the composite coating Method comprising a. In claim 5, Wherein said plasma electrolytic oxidation occurs at a voltage of 100-1000 V, a current density of 2-200 A / dm ² , and a continuous pulse frequency of 50-3000 Hz in a weakly water-soluble alkaline electrolyte at 10-55 ° C. In claim 5, Incorporating the functional compound into the pores of the coating is effected by electrochemical precipitation from an aqueous or organic solution, including the use of superdispersed powders. In claim 5, Incorporating the functional compound into the pores of the coating is by chemical precipitation from an aqueous or organic solution. In claim 5, Inserting the functional compound into the cavity of the coating is performed by chemical precipitation from the gas phase. In claim 5, Inserting the functional compound into the cavity of the coating is performed with the aid of a physical precipitation method. In claim 5, Inserting the functional compound into the cavity of the coating is done with the aid of friction-mechanical rubbing on using powders, rods and brushes. The method according to any one of claims 5 to 11, The finishing machining of the composite coating is selected from polishing, fine grinding, lapping, honing and precision finishing operations, and the apex of the protrusion of the oxide ceramic matrix layer until the actual size matches the required size (apex) until exposed.