Analysis of silt cavitation erosion resistance of Cr₃C₂/NiCr coating prepared by high velocity oxy-fuel thermal spraying

A Cr₃C₂/NiCr coating was prepared on 1Cr18Ni9Ti stainless steel by high velocity oxy-fuel (HVOF) thermal spraying. Phases and microstructures of the coating were analyzed by X-ray diffraction (XRD),transmission electron microscope (TEM) and scanning election microscopy (SEM),respectively. The cavitation erosion resistance and silt erosion resistance of the coating were evaluated under two experimental conditions (fresh water and water contained fine silt),and compared with hydro machine material 1Cr18Ni9Ti stainless steel. The result shows that the coating shows a layered structure and contains un-melted particles and some pores. The phases of the coating are composed of Cr₃C₂,Cr₇C₃,Cr₂₃C₆ and NiCr. The 1Cr18Ni9Ti stainless steel produces the work hardening,which results in the resistance to cavitation erosion. The Cr₃C₂/NiCr coating exhibits significantly higher microhardness than 1Cr18Ni9Ti stainless steel,which leads to the resistance to silt erosion of the coating. The mass loss of the coating usually happens at the edges of the pores while the cavitation damage of the 1Cr18Ni9Ti stainless steel happens at the grain boundary and twin boundary.