Cavitation erosion characteristics of a Fe–Cr–Si–B–Mn coating fabricated by high velocity oxy-fuel (HVOF) thermal spray

Abstract

A Fe–Cr–Si–B–Mn coating was prepared by high velocity oxy-fuel (HVOF) thermal spray on the surface of 1Cr18Ni9Ti stainless steel. Microstructures of the coating were investigated by X-ray diffraction (XRD), optical microscopy (OM) and scanning election microscopy (SEM), and the cavitation erosion resistance of the coating was evaluated using a GB6383-86 standard method in fresh water and compared with hydro-machine material ZG06Cr13Ni5Mo martensite stainless steel. The coating consisted of a Fe–Cr-rich matrix and several kinds of borides, the former comprised both amorphous phase and nanocrystalline grains. The nanocrystalline grains with a size about 10–50 nm further formed into an agglomerate-like structure with an average size of 100–500 nm. The coating had a significantly higher microhardness (HV 0.21008) than the comparing material ZG06Cr13Ni5Mo (HV 0.2260), which resulted in greater weight losses of ZG06Cr13Ni5Mo at the whole cavitation erosion process. It was found that the mass loss began at the edges of the pores or the interface between un-melted or half-melted particles and the matrix in the coating, while the mass loss was initiated at the lath interface of martensite in the ZG06Cr13Ni5Mo. The experimental results indicate that the HVOF thermal spray is a promising method to prepare the cavitation resistance coating.