The effects of temperature on friction and wear mechanisms during direct press hardening of Al-Si coated ultra-high strength steel

The COF is found to be temperature dependent during initial sliding against a virgin tool surface. Whereas, for 10 consecutive strip draws, COF is only temperature dependent for the first samples over the temperature range from 400 °C to 750 °C. This would be due to the tribolayers which form in the tool-sheet contact during the test series. Conversely, the wear mechanisms active in this temperature range are temperature dependent: at higher temperatures (> 600 °C) an area of severe abrasive wear is found that precedes a thick layer of compaction galling while at lower temperatures, (< 600 °C) adhesive wear is dominant. Furthermore, the results show that particles leading to compaction galling are predominantly generated from the Al-Si coating and their size depends on temperature and are related to the fracture of the Al-Si coating.