A Comparative Study On WC Powder And Coatings Deposited By Detonation Spray

Detonation sprayed tungsten carbide coatings have been widely used due to its high quality wear resistance. With different process technology, WC powders feedstock differs in grain fineness distribution, wrap condition, etc. The characteristics of powder feedstock have an influence on decarburization of powder itself, decarburization of coatings, adhesion between the splats in coatings, and finally have an effect on the structure and mechanical properties of the coatings.WC coatings were prepared by DNB-3detonation system using two kinds of WC powder feedstock. First, grain fineness distribution, structure and phase composition were studied; then, two coatings were prepared and their structure, porosity, microhardness, elastic modulus, and wear resistance were compared; finally, characteristics of undeposited powder of original powder were studied to confirm the change of powder in the process of detonation spray. Coating is prepared using undeposited powder. The structure and mechanical property of the coating were studied to see if the undeposited powder feedstock can be reused. The main conclusions are as follows:(1) Powders with smaller size have a larger degree of decarburization during spray. With high percentage of adhesion phase and better wrap condition in the surface, the powder will have less decarburization. And if the wrap is uncompleted and WC directly exposed to air, the powders will suffer a serious decarburization.(2) If the percent of adhesion phase is higher and the wrap condition is better, the bond strength between the splats will be higher and the porosity of the coating is lower, the hardness and elastic modulus higher, the wear resistance better.(3) Not all the power will deposit to form coatings during the process of spray. Some part of the undeposited powder hit the substrate and broke into pieces; while some of them fly directly into the air.(4) After a simple process of undeposited powder, coating is deposited using detonation spray. And the mechanical property of the coating is comparable to the coating deposited with original powder, so the undeposited powder can be recycled.