The dependence of erosion-corrosion wastage on carbide/metal binder proportion for HVOF carbide-metal cerment coatings

Abstract

A series of erosion-corrosion (E-C) tests was carried out on hypersonic velocity oxygen fuel (HVOF) carbide-metal cement coatings specimens at elevated temperature under conditions that attempted to simulate the errosion conditions found in fossil-fired boilers. The coatings included tungsten carbide, niobium carbide, and titanium carbide with different fractions of metal binder phase. Angular SiO 2 quarts particles were used as the erodent materials for tests at both shallow and steep impact 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 swallow and steep impact angles, peak wastage occurred at an intermediate 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 contents. The effect of carbide size in the coatings was also investigated. Results indicated that E-C wastage reduced with reducing carbide size at both shallow and steep impact angles. The E-C behavior of carbide/metal cement coatings and the dependence of E-C wastage on metal binder content are related to the morphology of the coatings and characteristics of erodent particles.