Evaluation of erosion resistance for metal–ceramic composites and cermets using a water-jet testing apparatus

High-speed centrifugal water pumps sometimes suffer severe erosion when the cavity generated by the inlet stream collapses. Use of materials with improved fracture toughness and material hardness, such as metal–ceramic composites or ceramic materials, results in a high resistance to cavitation erosion. In the present study, water droplet impingement erosion tests were conducted to evaluate the cavitation-erosion resistance of hard materials, as the process that occurs during water droplet impingement erosion is analogous to that of cavitation. A water-jet testing apparatus, which created robust and reliable testing conditions, was used in the present study. The incubation period and damage-depth rate were used to evaluate the erosion resistance of both metal–ceramic composites, which were generated by precipitation hardening of stainless steel and TiC particles, and WC cermet materials. The metal–ceramic composite showed two phases of erosion damage. The damage-depth rate in the first damage phase was low due to the removal of debris from the TiC particles and the metal substrate. The higher damage-depth rate in the second region was attributed to the removal of either ceramic particles or grains from the surface. Some of the cermet materials showed immediate and remarkable damage with no incubation period due to corrosion of the metallic binder by tap water. Consequently, the erosion resistances of the metal–ceramic composites and the cermets, as evaluated based on the incubation period and the damage-depth rate, were related to the average material hardness in a logarithmic scale. The high erosion resistance was attributed to the increased hardness of the composites and the cermets.