VACUUM PLASMA-SPRAYED ZIRCONIUM CARBIDE COATINGS

Zirconium carbide coatings were deposited on graphite substrates using the vacuum plasma spray process. Controlled vacuum spraying of pure c ompound powder was used to maintain the coating purity and to minimize the porosity of the sprayed carbide. Coating optimization studies wer e conducted using a Taguchi statistical fractional-factorial design of experiments. The effects of three plasma processing variables (i.e. g un current, argon primary gas Bow, hydrogen secondary gas flow) were e valuated relative to the coating attributes of thickness, porosity, su perficial hardness, and microhardness. As-sprayed coating qualities ar e discussed with respect to the influence of the processing parameters . In addition, the effect of annealing the carbide samples in an argon atmosphere at 1998 K, 2373 K, and 2673 K for 1 h was studied.