Composite coating and method of its manufacture

 

(57) Abstract:

The invention relates to multifunctional materials and can be used to form wear resistant composite coating on friction surfaces of the bearing and slide bearing, guides and other nodes of the machine parts from aluminum and its alloys. Composite coating contains a base of aluminum or its alloy and a layer of pyrolytic chromium, between the base and the layer of pyrolytic chromium placed intermediate layer oxidability. The thickness of the layer of pyrolytic chromium is 5-50 μm, and a layer of oxalacetate 50-300 μm. Method of forming a wear resistant coating includes forming oxide-ceramic layer based on aluminum or its alloy with micro-arc processing and pyrolysis of chromium carbide, with a layer of oxalacetate perform open on the surface porosity 3-10%, and when the pyrolysis mentioned porosity filled with chromium carbide. Effect: increase the load capacity of the coating. 2 S. and 1 C.p. f-crystals, 1 tab., 2 Il.

The invention relates to multifunctional materials and can be used to form wear-resistant composite pin, made of aluminum and its alloy used in engineering and other industries.

It is known that one way to improve the reliability and service life of the parts and components of machines, devices and equipment in conditions of intense friction is the use of wear-resistant coatings. Wear-resistant sliding surface in friction pairs formed by coating on the surface of parts of high-strength coatings using various technologies of their formation, for example, polymers, composite materials, solid lubricants, metal-ceramic materials.

Known wear-resistant composite material and method of manufacture (ed. St. USSR N 221945, class B 22 F 7/04, publ. 1972).

In this technical solution working layer of wear-resistant material applied on the base material, thus to improve communication working layer with the basis cause of the intermediate bonding layer of metal in the manufacture of a composite material is heated in a neutral atmosphere to a temperature above the melting point of the cementing metal. As a result, it melts, providing a secure connection between the working layer and materiamage layer the copper.

A significant disadvantage of this material is the low load capacity of the working layer of tungsten carbide with localized (point or line) loading, as it is placed on the soft copper base, and it has a low hardness. To increase the load capacity requires a significant increase in the thickness of the working layer that with larger working surfaces leads to a significant appreciation of design, technology of its creation and, as a consequence, economic inexpediency of its use. In addition, the method of manufacture described material can not form the intermediate layer of copper on the substrate surface of aluminum and its alloy, the melting point of which is below the melting temperature of copper, which limits the scope.

There is a method of creating a wear-resistant oxide-ceramic coatings by the method of microarc oxidation on the basis of aluminum or its alloy (ed. St. USSR N 1200591, CL C 25 D 11/02, publ. 1989).

A significant drawback of oxide-ceramic coating is a high coefficient of friction in dry and boundary friction characteristic start and stop agennix with oxide-ceramic layer of the surfaces of the part. For this reason it is very important choose the best material and lubrication of the friction surface in contact with the surface of the aluminum oxide, which is not always possible for technological, structural, economic and other reasons, specific details, or the site.

Known analogues of the closest to the technical essence of the present invention is the coating of pyrolytic chromium and method of its manufacture. (Yurchenko A. D. and other Protective coating of pyrolytic chromium: technology, properties, results of testing and application. - Dmitrovgrad, 1994, S. 3-5). In this technical solution working layer of chromium carbide is applied on the basis of aluminum or its alloy by pyrolysis liquids "Burgos" at the temperature of deposition 430. ..450oC, the vapor pressure in the deposition chamber 0,1...1,0 PA.

A significant disadvantage of this coating is a low load capacity when it is applied to aluminum or aluminum alloy, as the layer of pyrolytic chromium, placed on a relatively soft base, pressed at a localized contact or linear loading. However, as the research showed, the increase in thickness deposited on the aluminium to olivosvicente significant internal stresses, promoting delamination of the coating, its destruction and, as a consequence, the loss of functionality of the node.

The objective of the invention is to provide a wear resistant composite coating and its method of preparation, allowing to obtain increased load capacity.

To solve the problem in composite coating on a base of aluminum or its alloy and containing a layer of pyrolytic chromium carbide, according to the invention, between the base and the layer of pyrolytic chromium carbide is placed intermediate layer from oxalacetate. The thickness of the layer of pyrolytic chromium carbide is 5-50 μm, and a layer of oxalacetate 50-300 microns.

In the method of forming a wear resistant coating including deposition of chromium carbide by pyrolysis on the basis of aluminum or its alloy according to the invention, prior to deposition of chromium carbide on the basis of aluminum or its alloy using microarc oxidation to form a layer of oxalacetate with open porosity 3-10%, which when the pyrolysis is filled with chromium carbide.

The best combination of physical and mechanical properties of adjacent materials in the coating provides a low coefficient of tridecylamine due to its inherent high strength and high (up to 300 microns) thickness. Low coefficient of friction provides a surface that is relatively thin working layer of chromium carbide. Due to the small thickness of this layer has a low level of residual stresses, and its penetration into the pores of oxalacetate not only provides high adhesion and high strength properties of the composite coatings due to the reinforcement of oxalacetate chromium carbide. When this reached the load capacity of the composite coating significantly exceeds the load capacity of its components separately (pyrolytic chromium carbide and oxidability).

Reinforcement carbide chrome oxalacetate with the formation of strong boundary layer is provided by performing oxalacetate overlooking its outdoor surface then occupying 3-10% of the surface and having a diameter of 1 to 5 μm, and maintaining during the pyrolysis of ORGANOMETALLIC compounds (liquid "Burgos") vapour pressure 2-8 PA.

High adhesion between the layer of oxalacetate and a substrate of aluminum or its alloy is immediate formation of the substrate material.

The above values of the parameters of the coating layers, and the method of their formation is cytokeratine 50-300 microns attributable to the following. When the thickness of the layer oxidability less than 50 microns are open on the surface of the pores extend to considerable depth (40-60% of the thickness of the coating) and the local loading of oxalacetate rasklinivanie chromium carbide and prolamines at relatively low contact pressures. The creation of the thicknesses of the oxide-ceramic layers more than 300 μm is not economically feasible due to the sharp increase in the cost of their formation.

Rational layer thickness of oxalacetate are selected in the range of 50-300 μm based on the loading conditions of a certain part in the operation.

In Fig. 1 shows the microstructure of the composite coating.

In Fig. 2 shows the microstructure of the boundary layer between oxidability and chromium carbide layer.

Composite coating consists of oxalacetate Al2O3(mainly because of Al2O3and-Al2O3particles) formed directly from the substrate material (aluminum or its alloy) and a deposited layer of pyrolytic chromium carbide (Cr-CrC) (Fig. 1). The outer pores oxidability filled with chromium carbide (Fig. 2), which generally provides increased load capacity of the composite coating.

On the outer layer of the sample material from aluminum formed using microarc oxidation layer oxidability Al2O3( basically-Al2O3and-Al2O3particles) with a thickness 40, 50, 100, 150, 200, 250 and 300 μm, with 7. . .9% open on the surface of pores with a diameter of 1.5-3 μm. The formation of the coating was carried out in the electrolyte based on the distilled water with the addition of 3 g/l solution of liquid glass with module 3 and a density of 1.5 g/cm and the addition of 2 g/l of sodium hydroxide NaOH at a voltage of 420 V and a current density of 20 A/DM2. Then on the layer oxalacetate was coated with the layer of chromium carbide by pyrolysis liquids "Burgos", which is a mixture of bissenova derivatives of chromium, mostly baatil and ethylbenzothiazolium. This liquid "Burgos" contains an additive to 3.5% of the volume of dimensional ether (C6H5CH2)2O. the Process of deposition of particles of chromium carbide on the surface of the heated parts produced under the following conditions:

- temperature vapor - 260oC;

- vapor pressure in the chamber of the deposition - 7 PA;

- the temperature of the substrate 430oC.

Options include layers of composite coatings and the results of comparative assessment of their prochnosti the implementation and the method of manufacturing a wear-resistant composite coatings provide increased load capacity.

1. Composite coating on a base of aluminum or its alloy and containing a layer of pyrolytic chromium carbide, characterized in that between the base and the layer of pyrolytic chromium carbide is placed intermediate layer from oxalacetate.

2. The floor under item 1, characterized in that the thickness of the layer of pyrolytic chromium carbide is 5 to 50 μm, and a layer of oxalacetate 50 to 300 μm.

3. A method of manufacturing a composite coating comprising precipitation of chromium carbide by pyrolysis on the basis of aluminum or its alloy, characterized in that prior to deposition on the basis of aluminum or its alloy using microarc oxidation to form a layer of oxalacetate with an open porosity of 3 to 10%, which when the pyrolysis is filled with chromium carbide.

 

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