Influence of Cr-Rich oxide scale on sliding wear mechanism of ferritic stainless steel at high temperature

The tribological tests of a ferritic stainless steel (FSS) 445 in contact with high-speed steel (HSS) were performed on a high-temperature pin-on-disc tribometer. Wear exhibited significant difference when the FSS 445 was oxidised with a Cr-rich oxide scale on the surface. The HSS pin displayed adhesive wear when there was no oxide scale on the stainless steel disc, and in the early stages, the coefficient of friction fluctuated significantly, but the level of wear changed as Cr2O3 particles formed. The wear was then reduced, and the coefficient of friction remained stable. The Cr-rich oxide scale which formed on the stainless steel was able to stabilise the coefficient of friction, to reduce the wear rate and to help form a glazed layer on the HSS surface. The abrasive wear of the HSS pin took place at 850 °C, indicating that the hardness of the Cr-rich oxide scale increased as the temperature decreased.