Creep properties in similar weld joint of a thick-walled P92 steel pipe

Abstract

The creep behaviour of a welded joint of a real thick-walled P92 steel pipe was investigated at 600 and 650°C and a stress ranging of 60–250MPa using uniaxial tensile creep tests. Creep smooth cross-weld specimens were machined from different positions of the weld representing the welding sequence. Following analysis of creep data, all creep tests were performed in the region of power-law creep. The rate-controlling creep deformation mechanism is most probably climb of intergranular mobile dislocations for both the weld and base P92 steel. The creep resistance of the weld joint was lower than that of the base metal. No substantial differences were found in the minimum creep, the time to fracture and creep ductility for creep specimens taken from different locations of the weld. The fracture morphology of the crept welded specimens was found to be a mixture of transgranular ductile and intergranular mode. The fracture locations were found to shift from the weld metal in the higher stress region to the heat affected zone in the lower stress region. Many cavities formed at grain boundaries during creep. It was considered that the coarse precipitates of Laves phase acted as the preferential nucleation sites for cavities.