Advanced functionalisation and numerical simulation of the boundary layer by deformation-induced martensite on bearing rings through bulk metal forming

Abstract

Abstract. The phase transformation of metastable austenitic steels caused by externally superimposed strains during cold forming increases the material strength in addition to strain hardening. Although numerous research papers have described the basic effects of the phase transformation from metastable austenite to martensite, it is not yet applied in the dimensions of common bulk formed components. Thereby the functionalisation of deformation-induced martensite to increase the material strength specifically at heavily loaded surfaces bears potential. However, the amount of deformation-induced martensite formation within a forming process is limited through the occurring strain hardening. In this paper an approach for an advanced functionalisation of this transformation through an adaption of the process is presented. The setup of a forming process is adapted, forming experiments are carried out at low temperatures and the specimens are investigated through hardness measurements (HV1), magnetic inductive testing (Feritscope MP3C) and microstructure analysis. The results were compared to distributions of plastic strain determined through FE simulations and showed a good correlation. It can be shown, that at cryogenic temperatures a significant increase of martensite formation is achieved.