A study on fatigue characteristics of S55Cr carbon steels with induction surface hardening for automotive ball bearings

Abstract

In this study, the effects of induction surface hardening on the fatigue characteristics of S55Cr bearing steel were investigated. The specimens were fabricated with various hardening depth and tested using a rotary bending machine. The S-N behavior and fracture mechanism of induction hardened specimens were investigated with the fractured surface observations. Typical 2-step S-N curves were observed for induction hardened specimens, and it was observed that most failures of lower S-N curves(>106 cycles) were associated with non-metallic inclusions which were introduced during induction hardening process. The fatigue strength of induction hardened specimens for the lower step of S-N curves was estimated by the fracture mechanics-based model based on the projected inclusion size, and it was shown that the fatigue strength of specimens failed with the internal inclusions was accurately estimated. © 2020 Korean Society of Automotive Engineers. All rights reserved.