Optimization and erosion wear response of NiCrSiB/WC-Co HVOF coating using Taguchi method

In this work, high velocity oxy-fuel (HVOF) thermal spraying was used to develop 65 wt% NiCrSiB-35 wt% WC-Co coatings on AISI 304 stainless steel substrate. Taguchi method was taken to optimize the spray parameters like oxygen flow rate, fuel flow rate, powder feed rate and standoff distance to obtain better erosion resistance at 90° impact angle. Standoff distance and powder feed rate were identified as the highly contributing parameters on the erosion wear loss. The important sequence of the spray parameter is standoff distance>powder feed rate>fuel flow rate>oxygen flow rate. The combination of 220 lpm of oxygen flow rate, 65 lpm of fuel flow rate, 28 g/min of powder feed rate and 300 mm of standoff distance was identified as the optimum condition for minimum erosion wear loss. The microstructure of the optimized coating was characterized using Scanning Electron Microscope (SEM) equipped with Energy dispersive spectroscopy (EDS), Optical microscope (OM), and X-Ray Diffraction (XRD). The microhardness, porosity and surface roughness of the coating was also measured. Finally, erosion wear testing of the optimized coating was conducted at 30°, 60° and 90° impact angle using hot air jet erosion testing machine. The SEM images of the erodent samples were taken to analyse the erosion mechanism.