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

The current study investigates the erosion performance of high-velocity oxy-fuel (HVOF) sprayed Alloy718-nanoAl(2)O(3) 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-Al(2)O(3)particles in the AL718 matrix. The highest micro-hardness was found to be1296 +/- 40 HV0.2 for Alloy718%-30%nanoAl(2)O(3) (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 degrees C at both low and high degrees impact angles (30 degrees and 90 degrees). 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 degrees impact angle as wear mechanism. The formation of cracks, craters and pullout was the responsible wear mechanism at 90 degrees impact angle for all deposited coatings. The developed coatings showed mixed behaviour of ductile and brittle mode of failure at 30 degrees impact angle and brittle mode of failure at 90 degrees impact angle for 30N coating.