Effect of tool coating on interfacial heat transfer coefficient in hot stamping of AA7075 aluminium alloys

Chromium carbonitride coatings have been gaining importance in the hot stamping industry due to their excellent wear and corrosion resistances that extend the lifetime of tools they are applied to. However, their effect on the heat transfer between materials being formed and the tools in a hot stamping process has yet to be studied. In the present research, the interfacial heat transfer coefficient values between a hot AA7075 workpiece and cold chromium carbonitride-coated tools were experimentally determined under different contact pressure conditions. A mechanism-based interfacial heat transfer coefficient model was subsequently developed for precise finite element simulations of the temperature evolution and cooling rate of the components being formed. The model enables the selection of the tool coatings to be optimized based on the requirements of the hot stamping process, with the thermal conductivity of the coating material determining its thermal performance and effect on interfacial heat transfer coefficient. (C) 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of the 17th International Conference on Metal Forming.