INTERPHASE REACTIONS IN FORMING PLASMA COATINGS

Nickel-plated powders and coatings of titanium and chromium carbides a nd borides are studied. Components of the starting powders react betwe en themselves and with oxygen from the atmosphere forming solid soluti ons, intermetallic compounds, and a shielding oxide film. During pulve rization the surface of particles does not lose a plated layer and nic kel metal is always available in the coating. In order to increase the life of coatings it is advisable to use powders with the minimum poss ible amount of oxygen which promotes decomposition of higher carbide. In order to reduce the amount of complex oxides and intermetallic comp ounds in the coating which make a brittle matrix it is recommended to use boride powders in a mechanical mixture with metal (alloy) powders.