CS252860B1 - The method of forming thin layers of tungsten carbide on an electrically conductive substrate - Google Patents

Abstract

The solution relates to a method of forming thin layers of tungsten carbide on an electrically conductive substrate, which is the cathode in an ion plating system with a stored electric potential relative to the ground of a vacuum chamber. The method of forming the layer is carried out by applying a plasma to the substrate, which is formed by vapors of subliming tungsten hexacarbonyl and ethyne or ethene, at a reduced pressure from the interval ΙΟ"3 Pa to 102 Pa.

Description

The invention relates to a method of forming thin layers of tungsten carbide on an electrically conductive substrate.

At present, there are a number of methods and technological approaches for creating thin layers of tungsten carbide. The most notable is the method of direct evaporation of tungsten carbide and! chemical methods (CVD), methods based on electro-spark mashashi and plasma spraying methods.

The methods used hitherto, including direct evaporation of tungsten carbide, are accompanied by difficulties associated with high evaporation temperatures, low evaporation and deposition rates, as well as difficulties in maintaining the desired ratio of tungsten to carbon in the layer. The chemical processes for the preparation of tungsten carbide layers are known, but very difficult to maintain the required preparation conditions, the layers are of low purity and the waste products are corrosive. The layers prepared by the above ¹ methods are also poorly adherent.

The above-mentioned drawbacks eliminate the process of forming thin layers of tungsten carbide on an electrically conductive substrate, which is based on the fact that on an electrically conductive substrate, which is a cathode on the negative electrode 0-10 kV polteueial tungsten or ethynyl eteint at a pressure of 10 ³ Pa iintervalu to 10 ² Pa.

Preferred methods for forming thin films of tungsten carbide on the electrically conductive substrate IPOD invention is that a layer of tungsten carbide is highly adhesive, dosaihujú the desired purity, the (možnoisťou dosiahnuitia vysofcej growth rate of the layer conceive a inanášamia, iktor depends on the rate of sublimation héxakiarbonylu tungsten ¹ by Another advantage of the method according to the invention is the possibility to influence the composition, structure, and mechanical properties of the layer, namely by the vacuum chamber pressure magnitude, ihexafcarboimyl tungsten sulphimation rate, the amount of ethine or ethene mapping, and the electrical parameters of plasma stimulation. According to the invention, the decomposition products of hexafcairbonyl of tungsten, tungsten and carbon monoxide have not been corrosive to the substrate and to the vacuum devices.

Said spósoib was verified by matting tungsten carbide layers onto high-speed steel and SK substrates. Hexacarhonyl of tungsten sublimated into the plasma space formed by impregnated ethine, resistance heating at pressures in a vacuum chamber 5. 10 ^-1 Pa, and a sublimation rate of 1 g. min ^-1 , negative electrode potential on the substrate versus a grounded vacuum coil of -2.8 kV when stimulating electrical discharge to the auxiliary electrode systems. Under these conditions. which lasted 20 min., tungsten carbide layers of 1.8 µm and microhardness 19 000 N were formed on the surface of the sub-wires. mm ² .

In another case similar to that of the predoalioim, hexaicairibonyl tungsten was sublimed by resistive heating into a plasma screen, which was however formed in ethene at a vacuum chamber pressure of 7.10 ² Pa, a sublimation rate of 0.7 g. min ¹ , and negative electrode potential on a 3 kV bucket steel substrate versus a grounded vacuum chamber. In this case, a 0.8 µm thick layer of microhardness of 18,000 N was formed on the substrate surface. mm ² . The tungsten carbide layer formed by this process has a finer structure compared to the layers of the previous example at a comparable high microhardness and friction coefficient in contrast to the steel.

The method of forming tungsten carbide layers can be used in the preparation of coatings on electrically conductive materials, possibly on materials pretreated with an electrically conductive layer, especially in the field of tools, tribological node components and components subjected to high stresses.

Claims (1)

SUBJECT A method of forming thin layers of tungsten carbide on an electrically conductive substrate that is a cathode in a negative electrical potential! A system characterized in that the electrically conductive substrate is subjected to plasma formed by sublimation vapors of tungsten hexagonal carbonyl and ethine, or ethene at a pressure of 10 -3 Pa to 102 Pa.