Comparative erosion performance of HVOF and LVOF sprayed NiCrSiBCFe-WC-Co coating

Abstract

Thermal spray coatings enhance one or more surface properties of engineering components. In this work, NiCrSiBCFe-WC-Co composite coating powder is deposited over SA213-T12 boiler steel using the high velocity oxy fuel spraying (HVOF) and low velocity oxy fuel spraying (LVOF) thermal spray methods to improve erosion performance. XRD and scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS) were used to examine the surfaces and constituents of as-deposited specimens, whereas SEM was used to investigate the eroded specimens. The erosion behaviours of developed coatings were investigated at 30° and 90° impact angles, 53 m/s and 400°C. XRD analysis of the HVOF coating showed an additional peaks of NiCo2O4, SiC and Ni2B with common peaks Ni, WC, W2C, Cr23C6 and C6(Cr,Co,Ni)23 to that of LVOF coating. HVOF-sprayed coating demonstrated higher microhardness and adhesion strength with lower porosity than LVOF-sprayed coating. The HVOF-sprayed NiCrSiBCFe-WC-Co coating demonstrated comparatively better erosion resistance than LVOF-sprayed NiCrSiBCFe-WC-Co coating, attributed to its superior properties. The mechanism of erosion, concerning the different characteristics of the coatings, is discussed.