Volume 41, Issue 2 (March 2013)
Stress-Relaxation Cracking Test for Welded Joints
Scientific and technological research concerning the underlying damage mechanism and the evaluation of adequate countermeasures of so called strain-age (SAC), stress-relaxation (SRC), or ductility-dip cracking (DDC) of service exposed base materials and welded joints suffers a lack of specialized testing methods, that are able to detect the most cracking susceptible area of the weld and result in a definite “pass or fail” distinction for every single experiment without leaving ambiguity in the interpretation of testing results. For these reasons an advanced four-point-bending technique was developed on the basis of the three-point-bending test established by van Wortel. The proposed method was applied for evaluating the cracking susceptibility of Alloy617B welded joints. The technique proved to be suitable for the base metal as well as for welded joints. All as-welded joints failed by interdentritic fracture within the weld and the site of fracture corresponded well with the maximum hardness location (HV10) evaluated after the bending tests. The proposed testing method distinctively provided evidence for reduced cracking susceptibility of welded joints caused by a post-weld heat treatment (980°C, 3 h, air). All heat treated joints surpassed the bending test without cracking underlining the unambiguity of the proposed testing technique.