Creep crack growth behavior in the HAZ of weldments of W containing high Cr steel

The creep and creep crack growth properties of W strengthened 11Cr-0.4Mo-2W steel welded joints have been investigated at 923 K. The joints were prepared using gas tungsten arc (GTA) welding and electron beam (EB) welding. Most of the joint specimens were ruptured in their heat affected zone (HAZ), and inevitably resulted in shorter creep lives than those of the base metals. The investigation of creep properties of simulated HAZ specimens showed that fine grains produced by heating around A(c3) were obviously responsible for the degradation of creep strength in welded joints. The creep lives of smooth specimens for EBW joints were about twice longer than those for GTAW joints, however brittle type IV fracture occurred even in the EBW joints with narrower HAZ width for long-term creep test. The FEM analysis used creep data from simulated HAZ specimens and so the experimental results for creep properties of welded joints could be explained. The creep crack growth properties in the HAZ of weldments were investigated using CT specimens. In the pre-cracked CT specimens, the crack initiation time was affected by mechanical constraint, whereas the difference of the crack growth rate between welded joints and base metal was negligible for the present high-strengthened steel. (C) 2002 Elsevier Science Ltd. All rights reserved.