Slurry Erosion of WC-Co Cermets and Ceramics

Abstract

Critical components in coal-liquefaction system, like letdown value trim and valve seats, are subject to severe wear from the erosive coal slurries. The slurry-erosion behavior of candidate valve trim and seat materials, like WC-Co cermets and hard ceramics (SiC, B₄C), was studied by measuring the wear rates in a slurry-jet impingement test and by examining the wear craters in a scanning electron microscope. The erosion rates of the WC-Co cermets decreased monotonically with decreasing cobalt volume fraction in the range 36.9 to 5.1 Percent. The mechanism of erosion changed systematically from one involving preferential removal of binder and release of undamaged WC grains in high-binder alloys to a uniform transgranular wear of WC grains in the low-binder alloys. A sintered grade of SiC and a hot-pressed grade of B₄C showed wear rates less than those of the cermets.