Hot erosion behavior of carbide–metal composite coatings

A series of hot erosion tests was carried out on several carbide–metal composite coatings using a nozzle type elevated temperature erosion tester. The coatings included high-velocity oxygen-fuel (HVOF) Cr3C2 cermet system and WC cermet coatings. 1018 low carbon steel and two arc-sprayed iron-base coatings were also tested for references. Bed ashes retrieved from different boilers were used as the erodent materials for tests at both shallow and steep impact angles. The morphology of specimens was examined by light microscopy and scanning electron microscopy (SEM) with EDS. The microhardness of the coatings and ash particles was measured. The erosion mechanism of coatings was also discussed. It was found that the all HVOF carbide cermet coatings showed much higher erosion resistance than 1018 steel and arc-sprayed iron-base coatings. Among the coatings tested the WC–17CrCo coating exhibited the highest erosion resistance. Among the HVOF Cr3C2 cermet system coatings the composite powder sprayed coatings showed higher erosion resistance than the blend powder sprayed coatings. The erosion behavior of the coatings is closely related to their microstructure, composition and the properties of erodent particles.