Abstract
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.
Highlights
INTRODUCTIONLike Automobiles, heavy duty machines, et., where the machine elements are subjected fatigue loading, Gas carburized and Induction hardened components are used
Reliability demands are stringentIn many applications, like Automobiles, heavy duty machines, et., where the machine elements are subjected fatigue loading, Gas carburized and Induction hardened components are used
The higher hardness resulted from the outer surface is due to the formation of martensite, which is obtained during the diffusion, and phase transformation of surface layers with self-quenching
Summary
Like Automobiles, heavy duty machines, et., where the machine elements are subjected fatigue loading, Gas carburized and Induction hardened components are used. The concept of surface integrity cannot be defined one dimensionally and does embrace the surface hardness, surface roughness, case depth or its geometrical shape, and the characteristics of the surface and the layers directly underneath it. It comprehends the mechanical, physical-chemical, metallurgical and technological properties. If the phase transformation is ferrite to pearlite to martensite the volume increases hindered by the bulk material produces compressive residual stresses. These stresses influence the mechanical properties like fatigue strength depending on their nature, magnitude and distribution across the body. This interest has its importance due to the fact that the presence of the residual stress interferes with the fatigue strength of the Materials [5]
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