Influence of the fabrication method on the wear resistance of hot forging dies

Tools used for hot forging are subject to simultaneously acting process-related high mechanical, tribological, chemical and thermal cyclic loads. In comparison to other manufacturing methods, the resulting load spectrum leads to a failure of the form-giving tool components after a short tool life. Wear is the main reason for die failure in hot forging processes, accounting for 70 % of all causes. Other kinds of failures are thermal and mechanical cracks as well as plastic deformation (a result of the loss of hardness due to the high thermal charge). In order to reduce wear, several kinds of wear reducing methods are subject of industrial applications as well as research works. For example, nitriding and optional thin hard coating or overlay welding are effective methods to increase the wear resistance of hot forging dies. Beside the process related stresses during the service, manufacturing of forging tools itself initializes microstructural changes in their subsurface zones. During fabrication, the general influence of the fabrication method on the tool lifetime has not been considered so far. The implementation of the knowledge of this influence into the fabrication process could lead to an increased productivity of hot forging processes without using expensive and complex wear reducing methods.