The tribological behavior of PVD coated work roll surfaces during rolling of aluminum

The use of PVD coatings for the mitigation of roll wear caused by high friction and adhesion in the roll gap during hot rolling of aluminum has been investigated. A tribo-simulator with a roll-on-block configuration was used for rolling AA1100 blocks at 25 °C and 450 °C under dry and lubricated conditions respectively. Six types of coatings, TiN, TiCN, TiAlN, CrN, Cr and DLC, were applied to M2 steel rolls and their performances compared with an uncoated roll. The CrN coating displayed a good combination of low friction and good aluminum adhesion mitigation behavior. The Cr coating's coefficient of friction (COF) and its surface area fraction covered with transferred aluminum were among the highest. The TiAlN coating had the lowest COF under hot rolling conditions with evidence of an oxide layer that was observed to delaminate from the rest of the coating. The DLC coating displayed the highest COF during hot rolling but the lowest during cold rolling. It had one of the lowest aluminum transfers to its surface under both cold and hot rolling conditions. The high friction was attributed to the transfer of a carbonaceous layer from the DLC coating to the aluminum surface.