Revealing residual stress and high-temperature mechanical performance of laser-welded P91 steel for fusion power plant components
The extreme working conditions of the in-vessel components in nuclear fusion reactors require remote laser-welding for maintenance. However, this process induces heterogeneous residual stress, which can interact with microstructures, degrading mechanical properties. Involving the high-temperature operating environment can further sophisticate the degradation. Here, the residual stress distribution of laser-welded P91 joints was evaluated, where the peak residual tensile stress (~ 150 MPa) is observed at the fusion zone and heat affected zone (FZ/HAZ) interface, whereas the highest compressive stress (~550 MPa) is located at HAZ and base material interface. The correlation between microstructures, fractography, residual stresses and mechanical properties was established to investigate deformation mechanism at room and high temperatures. While the microstructural strengthening phenomenon is overwhelming in tension, residual stress effect in micro-hardness is much identical. The results provide insight into maintaining structural integrity for this critical engineering challenge.