HVOF sprayed coatings of nano-agglomerated tungsten-carbide/cobalt powders for water droplet erosion application

Water droplet erosion damage is due to the high speed impingement of several hundred micron-sized water droplets on solid surfaces. Thermal sprayed tungsten carbide based coatings show potential to combat such erosion problems. However, there are considerable discrepancies about their erosion performances in the literature. In the present work, the microstructure, phase composition and mechanical properties (micro-hardness and fracture toughness) of WC-Co coatings are studied in relation to their water droplet erosion performance. Coatings were deposited by high velocity oxygen fuel (HVOF) process and they were tested as-sprayed in WDE erosion system. The nano-agglomerated WC-Co powders are in either sintered or non-sintered conditions. The WDE tests were performed using 460 μm water droplets at 250, 300 and 350 m/s impact velocities. The coating with homogeneous microstructure shows up to 7 times less erosion rate than Ti6Al4V, while the coating with heterogeneous microstructure shows worse erosion rate compared to Ti6Al4V.