HIGH VELOCITY AIR GAS PLASMA SPRAYING OF (Ti, Cr)C–32 wt.% Ni COATED POWDER

Abstract

The influence of air fuel thermal spraying parameters (plasma torch power, spraying distance, plasma gas flow, anode diameter) of (Ti, Cr)C–32 wt.% Ni coated powder on the characteristics of resultant coatings (structure, microhardness, porosity, phase composition) is studied. The experimental procedure is designed using the mathematical planning method. The experimental data are processed to derive regression equations, determining the quantitative dependence of average microhardness and stability of microhardness characteristics on spraying process parameters. It is found that plasma torch power and plasma gas flow have the greatest impact on microhardness of the coatings and ∆X/H^av parameter, which characterizes the reproducibility of coating properties. The spraying distance has hardly any influence on the properties studied within the test range (160–220 mm). The hardness of coatings produced from the (Ti, Cr)C–32 wt.% Ni coated powder (12.15–14.58 GPa) is higher than that of the coatings obtained by air fuel thermal spraying of a mechanical mixture of 75 wt.% (Ti, Cr)C + 25 wt.% NiCr (5.3–12.6 GPa).