Cyclic deformation behaviour of a superaustenitic stainless steel and the role of embrittling precipitates formed during welding

The monotonic and cyclic deformation behaviour, including the role of grain boundary precipitates, have been studied for a superaustenitic stainless steel with nominal composition Fe-0.01C-24Cr-22Ni-7.3Mo-3Mn-0.5N (wt%). Pronounced planar slip modes, caused by the high N content, were identified as well as indications of persistent slip band formation during cyclic deformation. Cyclic softening at the initial part of the life-time followed by fairly constant saturation stresses was observed. Grain boundary precipitate structures, resembling those found in heat-affected zones of welds, greatly affect the fracture mode in tensile straining but have a minor influence on the flow stress levels and elongation to fracture. Cyclic straining causes an earlier onset of micro cracking in material containing grain boundary precipitates.