Resistance to slurry erosion by WC-10Co-4Cr and Cr3C2 − 25(Ni20Cr) coatings deposited by HVOF stainless steel F6NM

Abstract

Hydroelectric turbine machinery experience extreme wear and tear due to slurry erosion and is one of the leading causes for the unplanned shutdown of hydro power plants. The coatings produced by High-velocity oxy-fuel (HVOF) thermal spray process on different hydro-turbine parts is known for improving wear resistance. In the present study, WC-10Co-4Cr and Cr3C2 − 25(Ni20Cr) coatings were sprayed by HVOF process on F6NM stainless steel of Dul-Hasti hydro-power plant turbine material. The slurry erosive wear studies of developed coatings was performed using high speed slurry erosive wear tester. Sediments collected from Dul-Hasti power plant dam site was taken as erodent material. The effect of four parameters specifically rotational speed (500–1250 rpm), slurry concentration (25–40 wt%), sand particle size (125–425 μm), and test duration (450–900 min) on slurry erosion of coated materials was studied. It was observed that among all the developed three coatings, the WC-10Co-4Cr coated samples has shown superior erosion resistance compared to Cr3C2 − 25(Ni20Cr) coated samples due to its improved micro-hardness. Both the developed coatings were observed to be useful in enhancing the erosion resistance of F6NM steel significantly. Erosion mechanism were studied in detail using SEM. The properties such as hardness and porosity were also examined.