Abstract

Air plasma spray coatings of three different WC-12%Co powders based on the powder manufacturing methods were conducted. S&F (Sintered and Crushed) WC-12%Co and NiCrSiB mixed powder with different ratio were also sprayed. The best wear resistance of S&F WC-12%Co coating was mainly due to its high hardness related with large amount of homogeneously and uniformly distributed retained carbides. The wear resistance of blend coatings increased with increasing WC-12%Co weight percent which was associated with the fact that the wear resistance of all coatings increased with increasing hardness and decreasing friction coefficient. But the exact relation of wear resistance with cohesive bond strength could not be found. The dominant wear mechanisms of WC-12%Co coatings were adhesive wear, tribo-film formation by material transfer, fatigue crack, particle (splat) fracture and delamination (spallation of coating layers). In the case of blend coatings, when the weight percent of WC-12%Co was small plastic deformation and abrasive mark (or scratching ) by asperity and/or hard particle were observed. with increased weight percent of WC-12%Co the wear mechanism was closer to that of WC-12%Co coatings where no plastic deformation and abrasive mark was observed.

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