Effects of Heat Treatment on Tribological Behaviour of Al–Si Coated 22MnB5 and SKD61 Tool Steels in Hot Stamping

In this study, we investigated the heat treatment effects on tribological behaviour between Al–Si coated 22MnB5 and SKD61 tool steels in hot stamping process using a high temperature tribosystem developed based on a strip drawing method. Heat treatments were conducted at 900 and 930 °C for durations of 220–600 s prior to friction testing. The results indicated that variations in heat treatment significantly impact porosity, oxide formation, and intermetallic compounds, thereby altering wear behaviour. Differences in heat treatment conditions led to variations of the total heat applied to the steel sheets, which influenced the diffusion of Al into the substrate and Fe into the coating. These diffusional differences underlay the distinct porosity, oxide formation, and intermetallic composition observed with each treatment, which in turn impacted wear behaviour. Under conditions of 900 °C for 220 s, unalloyed aluminium remained on the surface, intensifying adhesive wear due to increased adhesion to the tool. In contrast, at 930 °C for 220 s, aluminium alloying was promoted, forming a substantial Fe₂Al₅ phase that increased adhesive wear. Under conditions of 900 °C for 600 s and 930 °C for 600 s, the increased temperature and duration influenced porosity levels, with the higher porosity observed at 930 °C for 600 s, leading to increased debris formation and enhancing adhesive wear. These findings provide the potential to optimise wear behaviour and tool life in hot stamping applications by adjusting heat treatment parameters.