Friction induced oxidation behavior of high velocity arc sprayed Fe-Al coatings during high temperature wear

The friction induced oxidation behavior of Fe-Al intermetallic coating during high temperature sliding wear from room temperature to 650°C is investigated using a ball-on-disc tribotester. The coatings are deposited onto 20 g low carbon steel substrates using high velocity arc spraying and cored wires. The results indicate that the decrease of friction coefficient with the temperature increase is caused by the development of protective oxide layers (composed by Al₂O₃, Fe₃O₄ and Fe₂C₃) on the worn surface during sliding wear, which act as a solid lubricant. And dynamic oxidation and hot pressed thermal sintering of wear particle are formation mechanisms of the protective oxide layers. The splats on the wear track delaminate firstly and turn into wear particles during sliding wear; after wear particle breaking-up, dynamic oxidization, and oxide powders formation under rolling and friction heat, the protective oxide layers are formed by hot pressed thermal sintering and coated on the sliding surface. The Fe₃Al and FeAl intermetallics with higher strength and hardness at elevated temperatures in the coating can effectively resist the pressing-in and micro-plowing of Si₃N₃ ball, thus the protective oxide layers on the worn surface are not easy to scale off.