Influence of in-service thermal softening on wear and plastic deformation in remanufactured hot forging dies

Abstract

The need for economic and greener production methods necessitates remanufacturing of used hot forging dies. However, it has been reported from industries that the remanufactured forging dies show higher wear rate, and plastic deformation as compared to new dies. In this work wear and plastic deformation behaviour in new, and remanufactured hot forging dies at different stages of forging cycles are experimentally studied. Die geometry was digitised using three dimensional optical scanner to analyse the wear depth, and plastic deformation. Compared to new dies, significant wear and plastic deformation was found in remanufactured dies. Since in-service microstructural changes are expected to influence wear and plastic deformation behaviour, microhardness tests were conducted on die specimen to measure the variations in hardness from surface to core regions of die. This study reveals that a thermally softened layer grow on the die surface with each forging cycle and in subsequent cycles, this layer gets removed by in-service wear and plastic deformation. In addition, the core hardness in new and remanufactured dies was found to decrease with increasing hot forging test duration. Consequently, remanufactured dies exhibits a lower core hardness, as compared to new dies, which eventually results in higher wear loss and plastic deformation.