Functionally Graded Tungsten Carbide Cobalt Coatings Fabricated by Detonation Gun

Abstract

Fabrication of two different types of functionally graded tungsten carbide cobalt (WC-Co) coatings has been tried by using detonation gun to enhance both the hardness in the surface region and the toughness of the coating. Five layers with a continuous compositional change of 75 to 92 wt.% of WC were sprayed to obtain ‘layer-structured gradient’ coatings. Each layer was controlled to have both minimum porosity and minimum phase decomposition of WC. New types of ‘continuously graded’ coatings were also fabricated to eliminate any obvious interfaces between layers by the ‘shot control method’ of detonation gun spraying. The wear resistance of these coatings was measured and compared to that of conventional WC-Co coatings by using dry sand abrasion tests under the condition of 20kg load and 200rpm rotating wheel. Present functionally graded coatings revealed more improved wear resistance than that of conventional coatings.