Abstract
A good corrosion resistance in combination with a relatively high strength make the nitrogen alloyed duplex steel 1.4462 (X2CrNiMoN22-5-3) favorable for the applications in chemical industry, paper and cellulose production, food industry and sea water piping. The stainless steel is therefore a very good choice for structural applications, where innovative joining processes such as laser beam welding are required. In case of 1.4462 steel welds show higher strength in comparison to that of the base material. In spite of usually acceptable static strength level, fatigue and damage tolerance characteristics of the laser beam welded 1.4462 joints are relatively poor due to inherent welding-induced defects, which are inevitable results of the laser beam welding process. The detrimental effect of defects is further enhanced by the formation of hard and notch-sensitive dendritic two-phase microstructure within the welding seam. In the current work, the quality of laser beam welded joints was characterized in terms of weld morphology, microstructure and mechanical properties. A particular emphasis of the present study is placed on investigating the effect of various welding defects on the high-cycle-fatigue performance of laser beam welded joints. Furthermore, a model to predict the fatigue properties in the high cycle fatigue regime is proposed. The fatigue-life assessment model has been developed for internally flawed materials based on the fracture-mechanics approach, which takes into account the short-crack effect.
