Comparison of Nondesturctive Stress Measurement Techiques for Determinatuion of Residual Stresses in the Heat Treated Steels

Service life and performance of the case-hardened machine parts are greatly dependent on the residual stress state in the surface layers which directly affects the fatigue behavior. Recently, all industrial sectors have been requested for a fast and non-destructive determination of residual stress. This study aims to monitor of the variations in surface residual stress distributions in the carburized 19CrNi5H steels by means of non-destructive and semi-destructive measurement techniques, Magnetic Barkhausen Noise (MBN), X-Ray Diffraction (XRD), and Electronic Speckle Pattern Interferometry (ESPI) assisted hole drilling. Microstructural investigation by optical and scanning electron microscopy, hardness measurements, and spectroscopy analysis were also conducted. To comprehend the differences in the surface residual stress state, 19CrNi5H steel samples were carburized at 900 degrees C for 8, 10 and 13 hours, and then, tempered in the range of 180 degrees C and 600 degrees C. Residual stress measurements carried out by XRD and ESPI assisted hole drilling showed that the compressive residual stress state exists for the case-hardened samples throughout the case depth regions, and the magnitude of the compressive residual stress decreases as the tempering temperature increases. MBN measurements showed that the BN activity increases with decreasing carburization time and increasing tempering temperature. It was concluded that MBN technique could be used to measure the surface residual stress distributions with a proper calibration operation.