INFLUENCE OF PLASMA SPRAYING CONDITIONS ON THE MICROSTRUCTURE AND FUNCTIONAL PROPERTIES OF WC-Cr-Ni METALOCERAMIC LAYERS

The article presents the results of research on the impact of the conditions of plasma spraying on thickness and porosity, as well as the erosion resistance of WC-Cr-Ni metaloceramic coatings. It was shown that the selection of current intensity – 450 A and flow rate H2 = 5 dm /min and Ar = 68 dm/min allows obtaining a coating with a thickness of approx. 177 μm and low porosity <6%. At the same time, this coating is characterised by the greatest hardness – 758 HV0.5, and the best erosion resistance at room and elevated temperature. The analysis of test results indicates that lower current and hydrogen content in the plasma stream do not ensure sufficient melting of the metallic matrix of the powder – Ni and Cr, and thus greater brittleness of the coating and its lower erosion resistance. It was also found that an increase in plasma stream energy due to an increase in torch current or hydrogen flow rate may cause tungsten carbide to decompose in the plasma stream – the phase affecting hardness and abrasion resistance.