Determination of residual stress state in SAE/AISI 8620 carburized steel by non-destructive testing methods

Kaleli, Tuğçe
Industrial performance of the carburized steels is mainly dependent on the residual stress state in the carburized layer that is controlled by the process parameters such as carburizing temperature and time. Non-destructive evaluation of the material properties and residual stress state has been gained importance for industrial applications due to its advantages such as measurement speed and complete control possibility of the components by automation. The aim of this thesis is to investigate the efficiency of magnetic Barkhausen noise (MBN) method for determining the residual stresses and monitoring variations in residual stress state in AISI/SAE 8620 steel. For this purpose, MBN measurements were performed to observe residual stress state on a series of samples prepared by changing carburizing time and tempering temperature, and then, the results were compared with those of X-ray diffraction methods. Microstructural examinations and micro hardness values were also investigated to analyze the results of the measurements. Increase in the carburizing time up to critical level caused to increase the compressive residual stresses in the carburized layer that is detected as a reduction in MBN emission. Moreover, it was observed that changing tempering temperature causes the change in the martensite morphology and different stress relaxation levels. A clear relationship has been observed between residual stresses and MBN signals. 


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Citation Formats
T. Kaleli, “Determination of residual stress state in SAE/AISI 8620 carburized steel by non-destructive testing methods,” M.S. - Master of Science, Middle East Technical University, 2017.