THE DEPENDENCE OF EROSION-CORROSION WASTAGE ON CARBIDE METAL BINDER PROPORTION FOR HVOF CARBIDE-METAL CERMET COATINGS/

A series of erosion-corrosion (E-C) tests was carried out on hypersoni c velocity oxygen fuel (HVOF) carbide-metal cermet coatings specimens at elevated temperature under conditions that attempted to simulate th e erosion conditions found in fossil-fired boilers. The coatings inclu ded tungsten carbide, niobium carbide, and titanium carbide with diffe rent fractions of metal binder phase. Angular SiO2 quartz particles we re used as the erodent materials for tests at both shallow and steep i mpact angles. E-C material wastage was determined from thickness loss measurements of the specimens. The morphologies of the specimens were examined by scanning electron microscopy. It was found that at both sh allow and steep impact angles, peak wastage occurred at an intermediat e value of metal binder content. At a shallow impact angle, this peak occurred on the side of higher metal binder contents, while at a steep impact angle the peak occurred on the side of lower metal binder cont ents. The effect of carbide size in the coatings was also investigated . Results indicated that E-C wastage reduced with reducing carbide siz e at both shallow and steep impact angles. The E-C behavior of carbide /metal cermet coatings and the dependence of E-C wastage on metal bind er content are related to the morphology of the coatings and character istics of erodent particles.