Potential of near-surface temperature regulation in hybrid additive manufactured forging dies

Recent advances in the field of additive manufacturing (AM) have enabled the utilisation of Laser Powder Bed Fusion (L-PBF) for tool steels under high load conditions. Design elements, such as internal cooling channels, which are not achievable through subtractive manufacturing can therefore be used to functionalise and optimise hot forging tools. Thermal control is crucial for hot forging dies as the performance and endurance of the tools is highly dependent on the input and dissipation of heat in the surface zone during forging. A modified forging tool with conformal internal cooling channels generated through a hybrid L-PBF manufacturing process was developed in prior work [1]. The objective in the presented research is the experimental evaluation of the effect of conformal temperature control in the novel tool concept on the temperature dependent tool deterioration mechanisms in forging conditions. The actively controlled water temperature was varied between room temperature for maximum cooling and 180 degrees C, representing an exemplary base temperature in steady state serial forging. After 1,000 cycles, the tool wear conditions are analysed optically and through destructive microstructure analysis to characterise the effect of the temperature management on the deterioration mechanisms. The results show a significant impact of subsurface temperature control on the wear mechanisms of forging dies. Abrasive wear can be limited to a minimum through internal cooling with major reduction in thermal loads. Increased base temperatures reduce run-in time but increase abrasion.