The effect of temperature on the unlubricated sliding wear of 5 CrNiMo steel against 40 MnB steel in the range 400–600°C

5 CrNiMo steel is used traditionally as hot forging die material in China. High temperature wear is a common failure mode of the steel. This paper deals with the sliding wear behavior of the steel in the temperature range 400°C to 600°C. The composition and features of the worn surface were analyzed using SEM, EDS and XRD. The oxidation of 5 CrNiMo steel under sliding wear condition at elevated temperature indicated that the oxide transfer layer formed on the sliding surface consisted of Fe₃O₄ and Fe₂O₃. The wear mechanism changed with the test temperature and the oxide transfer layer played an important part in the change in wear mechanism. At lower temperatures, wear was due to abrasive wear. From 500°C to 550°C, the oxide transfer layer presented a relatively compact morphology and the oxidational wear was the principal wear mechanism resulting in low wear rate at 500°C. When the test temperature was at 600°C, adhesive wear was predominant, and the wear rate increased greatly.