Erosion behaviour of HVOF sprayed Alloy718-nano Al2O3 composite coatings on grey cast iron at elevated temperature conditions

Abstract

The current study investigates the erosion performance of high-velocity oxy-fuel (HVOF) sprayed Alloy718-nanoAl2O3 composite coatings on cast iron. The effect of the addition of nano-Al2O3 reinforcement in the Alloy718(AL718) matrix was studied by varying the nano-Al2O3 content from 10wt% to 30wt%. Initially, the microstructural and phase analysis of the developed coatings was conducted. The as-deposited coating in the AL718matrix showed the well-scattered nano-Al2O3particles in the AL718 matrix. The highest micro-hardness was found to be1296 ± 40 HV0.2 for Alloy718%-30%nanoAl2O3 (30N) coating, which is around 3.56 times higher than the grey cast iron (GCI) substrate. The air-jet erosion test was conducted at 900 °C at both low and high degrees impact angles (30° and 90°). The 30N coating showed the maximum erosion resistance due to the higher micro-hardness and fracture toughness amongst all the deposited coatings. The increased nano-Al2O3 content enhanced the erosion resistance of the coatings by providing dispersion strengthening to the matrix. The formation of cavities, ploughing, lip formation and micro-cutting were observed in all deposited coatings at 30° impact angle as wear mechanism. The formation of cracks, craters and pullout was the responsible wear mechanism at 90° impact angle for all deposited coatings. The developed coatings showed mixed behaviour of ductile and brittle mode of failure at 30° impact angle and brittle mode of failure at 90° impact angle for 30N coating.