Hardness and failure assessment of a hot extrusion punch during service

Abstract

Abstract To explore the evolution of the microstructure, properties, and failure mechanism of a hot extrusion punch during service, a hot extrusion experiment was carried out on a home-designed testing platform, enabling multiple analyses at an elevated temperature of 950℃. The microstructure was evaluated using optical microscopy, scanning electron microscopy, and other analytical methods. The results showed that the punch could continue working 850 times before it failed. The primary failure mode was ascribed to local plastic deformation, accompanied by apparent oxidation and wear at the bottom and working area. The extended analysis also revealed that the ferrite content in the matrix increased in the entire working zone and that the overall microstructure exhibited a fibrous morphology instead of lath features, where the tiny carbide particles were homogeneously distributed. This suggested that significant plastic deformation occurred during service. Moreover, the carbide particles were further fragmented and well dispersed with plastic deformation.