Residual Stresses in Case Hardened Materials

Fatigue behavior of case hardened parts depend to a great extent on the type of residual stresses developed in the components. Topography and metallurgical effects were the two elements which contribute much to surface integrity. Micro hardness of the gas carburized (EN 33 and EN 36) and Induction hardened (AISI 1040 and AISI 6150) specimens obtained during experiments, showed that there was gradual decrease of hardness from surface to sub-surface. Results also showed that more the hardness and case depth, the more was the residual stress. The optimum results gave the maximum compressive residual stress in both the gas carburizing and Induction hardening process irrespective of the mechanisms involved in the process. The X-ray diffraction test showed that the distribution of residual stress was uniform both on the surface and beneath the surface. The magnitude and distribution of residual stress obtained from the experiment agreed with the FEM results found in literatures.