Micromagnetic characterization of residual stresses in vacuum brazed tool steel joints

Abstract

Abstract

Residual stresses have a significant impact on the quality and service life of brazed components. Therefore, a comprehensive understanding and reliable characterization of the residual stress state in brazed joints are essential. X‑ray diffraction (XRD) is regarded as the conventional method for residual stress analysis. However, its application requires specific safety regulations and qualified staff to ensure adequate radiation protection. These requirements make the procedure comparatively complex, time‑consuming, and costly. In this study, two micromagnetic methods, eddy current (EC) testing and magnetic Barkhausen noise (MBN) analysis, were investigated as potential methods for residual stress characterization. Both techniques are sensitive to residual stresses as well as to other material properties and are comparatively simple and rapid measurements. To evaluate their capabilities and limitations, spatially resolved EC and MBN measurements were performed on a vacuum-brazed tool steel specimen and compared with residual stresses determined by XRD using the cos(α) - method. The focus was on the spatial distribution obtained by the different measurement techniques and on the correlation between the micromagnetic signals and the XRD measurements. The EC and MBN measurements revealed distinct spatial variations across the specimen, while the XRD measurements showed less pronounced variations in the residual stress distribution.