Relationship Between Deep Case Carburizing and Residual Stress in Rolling Contact Service

The proposition that compressive residual stresses are beneficial in improving the service life of components subject to rolling contact fatigue is well documented. However, the exact nature of the relationship between effective case depth (ECD) and the residual stress state is not well understood for components with deep case depth (>0.050inches, 1.27mm). It is expected that compressive residual stresses will gradually transition to tensile stresses as the case depth increases beyond a threshold value. In addition, the strain-induced transformation of retained austenite and its influence on the residual stress state of components resulting from service will be explored. This study will measure the residual stress state of components prepared with various ECD before and after simulated service with the goal of determining where the compressive to tensile transition occurs. Residual stress and retained austenite measurements will be conducted using X-ray diffraction.