Creep fracture at stress concentrations in type 316 stainless steel weld metal

A comparative study of the creep fracture behaviour of as-deposited type 316 stainless steel weld metal and parent type 316 steel demonstrates that acceptable creep rupture properties can be obtained in this weld metal at 625 and 5500C. Using notched specimens it has been shown that the displacements required to initiate creep crack propagation decrease with decreasing applied stress. The associated incubation period required for crack initiation appears to increase with decreasing stress and then to attain a constant value. This observation probably relates to microstructural transformations occurring with increasing thermal exposure. Steady state creep crack growth rates in weld metal are comparable in magnitude with those in the parent material. The crack propagation behaviour can be related in detail to the microstructural features of the weld deposits in that the local ductility is deleteriously affected by second-phase precipitation, with cracking occurring preferentially along delta ferrite-austenite boundaries. (Auth.)