Optimization of Cooling and Lubrication for Nitrided and Ceramic-Coated Hot Forging Dies

Abstract

In order to enhance the tool life of hot forging dies, increasing the wear resistance of the forming tool surface is of great importance. In addition to thermal and thermo-chemical surface treatments, methods applying thin wear-resistant coatings gain more importance. Therefore, ceramic-based mono- or multilayer hard coatings are used in combination with a supporting nitride layer. Due to their low material-specific thermal conductivity, ceramic coatings have an increased sensitivity to abrupt temperature changes. To avoid such thermal shocks, an adjustment of the cooling behaviour is required. This paper presents the results of laboratory forging tests conducted under different cooling and lubrication conditions on nitrided dies with ceramic coatings. By means of a selective cooling of the forming tool surface and using boron nitride as lubricant the wear behaviour of the forging dies could be improved.