Synchrotron X-ray diffraction analysis of 2D residual stress distribution in the brazed joint of PCBN ceramic and M42 steel

Residual stress is a critical issue in ceramic/metal composite structure joints, yet reports on residual stresses in ceramic/phase-transforming metal joints remain scarce. In this study, the 2D residual stress distribution in a PCBN ceramic and M42 high-speed steel brazed joint is revealed for the first time using synchrotron XRD. The joint comprises a PCBN ceramic, a CuNi interlayer, and M42 steel. Notably, an abnormal residual stress distribution, with tensile stress present at both the surface and interface of the ceramic, is observed for the first time. The residual tensile stress near the ceramic interface exceeds 1000 MPa, and joint fracture occurs in the region of maximum tensile stress at the ceramic interface. Finite element analysis indicates that shrinkage of the CuNi layer dominates in joints formed below the phase transition temperature, resulting solely in residual compressive stress at the ceramic interface. In contrast, high-temperature XRD analysis and thermal expansion coefficient measurements confirm that the volume expansion caused by the phase transformation of M42 steel is a key factor contributing to the tensile stress at the ceramic interface.