Residual stress distributions in a P91 steel-pipe girth weld before and after post weld heat treatment

► Residual stresses in a pipe girth weld in P91 steel have been measured in both the as-welded and PWHT conditions. ► The highest tensile residual stresses coincided with the HAZ boundary and the microstructural region that is prone to type IV cracking. ► Compressive residual stresses were measured in the weld metal, in a location corresponding to the final weld pass. ► The location of the peak compressive stresses can be explained by the effect of solid-state phase transformation.