Phenomena and degradation mechanisms in the surface layer of die inserts used in the hot forging processes

Abstract The paper presents the results of studies on the analysis of the destructive mechanisms for die inserts used in the first operation of wheel forging process, and the results of laboratory tests obtained on specially constructed research position for testing thermal fatigue and abrasive wear. The results of investigations on the die inserts shown that the dominant destructive mechanisms for these tools are thermal fatigue occurring in the initial the exploitation stage and abrasive wear, which occurs later, and is intensified effects of thermo-mechanical fatigue and oxidation. The observed mechanisms resulting from the extreme conditions prevailing in the hot forging process and are caused by cyclic changes in thermal and mechanical loads. In order to better analysis and knowledge of phenomena associated with these mechanisms, the authors built a special research positions allow for a more complete analysis of each of the mechanisms separately under laboratory conditions, which correspond to the industrial forging processes. A comprehensive analysis of the inserts confirmed by tests on laboratory stands, showed the interaction between the thermal fatigue and abrasive wear, combined with the process of oxidation. The results showed that the thermal fatigue and destruction as a result of oxidation, very often occur together with the mechanism of abrasive wear, creating a synergy effect, causing the acceleration, the most visible and “easily measurable” processes abrasive wear.