Characterisation of short-length scale residual stress variations within an electron beam welded P91 Ferritic–Martensitic steel plate

In this research, an electron beam (EB) butt-welded P91 steel plate (~9 mm thick) is selected to measure longitudinal residual stresses (acting in the welding direction) using a promising residual stress measurement technique - the contour method. The EB weld causes short length scale residual stresses within the narrow width of the fusion zone with steep stress gradients lateral to the weld line, which presents a new challenge for the residual stress measurements. The special measures were taken for all main steps of the technique to improve its the spatial resolution, thereby the short length scale residual stresses were captured. The success of the measurement is assessed by comparing the contour method result to the neutron diffraction result, and a good agreement were found in the results of both the techniques. These results also shows that the contour measurement results successfully captured the steep stress gradient on both sides of the weld centre-line (0 mm) with tensile stress peaks situated just 2.8 mm apart. It is one of the best resolutions in residual stress length-scale in this component achieved in contour measurements. The contour method; High energy density welding (HEDW); Electron beam welding (EB); P91 steel; Wire electrical discharge machine (WEDM).