Strain Hardening of Heat Treated Nanostructured WC-17Co Coatings and Their Sliding Wear Behavior

Grain size, their distribution and geometry are important to study the dislocation behavior and grain boundary sliding of ceramic reinforced metallic composite materials. Grain size reduction has been shown to lead to significant improvements of the wear resistance in nanostructured materials. As the grain size decreases from polycrystalline to nanocrystalline range, abrasive wear resistance increases considerably from the increased hardness and volume loss following Archard’s law of wear. Further, the heat treatment effect on the content of the metallic binder in a ceramic-metallic (cermet) material is thought to increase the hardness with decreasing crystalline size, thereby improving the sliding wear behavior of materials. In this study, the high velocity oxy-fuel (HVOF) thermal spraying of nanostructured WC-17Co coatings with engineered ‘duplex outer coating’ is conducted. The microhardness and sliding wear studies of the coatings and their heat-treated counterparts are performed. The nanostructured coatings showed a significant increase in the microhardness and wear resistance when compared with those of the conventional microstructured coatings of the same composition. It is believed that the improved performance is related with the work hardening as well as dispersion hardening of the nanostructured grains in the deposited coatings.