Effect of die geometry on thermal fatigue of tool steel in aluminium alloy die-casting

Abstract

In this paper, die geometry and its effect on the thermal wear of H13 steel was evaluated during aluminium die-casting. During the investigations, an innovative dipping testing device was used. The process involved a cyclic aluminium alloy-melting die and water-cooling process, which allows a dominated cycle of thermal fatigue. The H13 tool steel was first prepared with different end geometries before been subjected to the cyclic heating and cooling (in a water basin) processes. During the heating and cooling processes, the produced hardness profile, surface cracks, and the microstructure of the samples were regularly analysed after a predetermined number of cycles. The effect of the sample end geometry, sample thickness, material of the sample, and the dipping test parameters on the thermal stress was also investigated. From the metallographic investigation of the sample surface, the thermal fatigue resistance of the sample was observed to be enhanced due to the improved die steel protection from oxidation. Oxides can permeate cracks at the corrosion pits and cause the propagation of cracks through the production of a tensile stress from the increased oxide volume at the crack tip. The improved thermal fatigue resistance of the tool steel was contributed by the ductility and high yield strength of the tool steel.