The effect of temperature and sliding distance on coated (CrN, TiAlN) and uncoated nitrided hot-work tool steels against an aluminium alloy

Adhesion and, in particular, the transfer of aluminium alloys to the bearing surface of a die are two of the main reasons for tool failure and the poor surface quality of products, especially at elevated temperatures. The present work was focused on the EN-AW6060 aluminium alloy׳s transfer initiation and the evolution to an AISI H13 hot-work tool steel, as well as CrN and TiAlN coatings in a cross-cylinder, single-pass, dry-sliding contact at room (20 °C) and elevated temperatures (300-500 °C). The contact was investigated in terms of the surface area and volume of the transferred aluminium alloy to the tool steel׳s surface, the topography of the wear trace and the corresponding change in the coefficient of friction. The results show a strong dependence of the tribological properties of the investigated materials on the temperature and only a limited dependence on the sliding distance, especially for the TiAlN coating. At room temperature the lowest coefficient of friction and the smallest amount of material transfer were measured for the TiAlN coating. At higher temperatures both the CrN and TiAlN coatings showed similar friction values and amounts of transferred aluminium alloy, while the nitrided hot-work tool steel exhibited an inferior tribological performance.