Comparative Study of Cavitation Resistant Coatings Produced by High-Velocity Oxy-Fuel

In many countries, hydropower is one of the main energy sources for electricity generation, e.g. China produces more than 17% (> 542 GW) of the hydropower of the world; in Brazil, more than 60% (> 114 GW) of its energy is produced by hydropower plants; Canada and the United States have also been huge hydropower plants. Hydropower works by converting the water flow into electricity in a generator unit or turbine. This work directly compares various HVOF coating materials regarding their characteristics, properties, and cavitation performance. Two cermets, WC and Cr3C2, with a sort of binders, are compared to three FeMnCrSi alloy compositions, as with carbon steel and CA6NM stainless steel benchmarks, the most employed materials for casting hydro runners. The materials deposited were different commercial carbides and experimental FeMnCrSi alloys. The cermets were WC and Cr3C2 commercial powders with different matrix and content. Comparing the groups, FeMnCrSi had the best performance, and WC had worse cavitation resistance, with Cr3C2 in between them. Since the cavitation erosion mechanism does not generate a homogenous volume loss of the hard grains and the binder but prefers eroding the binder low-resistant phase, surrounding the hard grains until detaching them completely.