Oxidation behaviour of D-gun sprayed Al2O3-3 wt% SiC coating

Thermally sprayed coatings are often used to protect metallic components from high operating temperature. The oxidation of such components exposed to high temperature decreases their life and performance. In this study, the high temperature oxidation behaviour of bare AISI 1020 steel, D-gun sprayed pure Al2O3 coated steel and Dgun sprayed Al2O3-3 wt% SiC coated steel are studied. The study is carried out at 900 degrees C temperature for 50 cycles in a muffle furnace. The phase and microstructure of the oxidized samples are studied by XRD and SEM methods respectively. Both the coated samples show improved oxidation resistance properties compared to the same of bare AISI 1020 steel. Between the two coated samples Al2O3-3 wt% SiC is found to have higher resistance against oxidation. In order to obtain hardness and fracture toughness properties of the oxidized samples Vickers micro-hardness and scratch test are performed respectively. Al2O3-3 wt% SiC coated sample is found to retain maximum amount of mechanical properties at elevated temperature. The formation of large number of cracks within the oxidized pure alumina coating is the main reason for the decrease in its mechanical properties.