INFLUENCE OF VELOCITY, CONCENTRATION, AND SIZE OF SILT PARTICLES ON EROSION OF THERMAL SPRAYED Ni/TiO2/Al2O3 COATINGS

Abstract

The presence of silt sediments in the flowing river is the primary reason for the severe failure of hydro-power turbine components. This study insights the effect of erosion parameters on the performance of two multi-dimensional novel compositions (namely Ni-40TiO2 and Ni-20TiO2-20Al2O3) developed on the CA6NM turbine steel by high velocity flame spray (HVFS) method. The Ni-40TiO2 coating with lower porosity, higher fracture toughness, and microhardness, showed the highest slurry erosion resistance than the other counterparts. This outstanding performance is attributed to the uniform distribution of the multi-dimensional TiO2 grains in the coating, which effectively reduces the material loss rate during slurry erosion. The Ni-40TiO2 coating indicated a mixed mechanism of material removal, while the brittle mechanism was observed in the case of Ni-20TiO2-20Al2O3 coating. A model has been proposed to estimate the erosion rate of these proposed coatings.