Parametric optimisation of high-velocity oxy-fuel nickel-chromium-silicon-boron and aluminium-oxide coating to improve erosion wear resistance

Nickel (Ni) based alloy coatings are gaining momentum due to its superior mechanical properties contributed by the dispersion of hard carbides and borides, which is substantially influenced by the processing technique. Accordingly, this work investigates High-Velocity Oxy-Fuel (HVOF) thermal spraying of Nickel-Chromium-Silicon-Boron (NiCrSiB) and Aluminium Oxide (Al2O3) at a 60:40 (wt%) ratio on AISI304 stainless steel substrate. The influence of HVOF spray parameters such as oxygen, fuel, and powder feed rate in addition to standoff distance on the erosion resistance was studied. The parametric model identified the rate of powder feed and standoff distance as the two most significant parameters affecting the erosion behaviour. The optimum parametric values for oxygen, fuel and powder feed rate was identified as 260 lpm, 65 lpm and 28 g min−1 respectively at a standoff distance of 250 mm for the highest wear resistance. The results of this study show that that NiCrSiB-Al2O3 HVOF coating features a ductile erosion behaviour and offers 1.6 times more wear resistance at a 90° impact angle in comparison to 30°.