Evaluation of weldability of nickel-base alloy weld materials with high chromium content

Abstract

Nickel (Ni) -base alloy 82 weld material is widely used for the primary reactor components of boiling water reactor (BWR). Although alloy 82 has shown excellent service performance for BWR application in terms of material reliability, several experiences have recently been reported regarding stress corrosion cracking (SCC) in welds associated with alloy 82. The present study aimed at enhancing the SCC resistance of the weld material by developing and evaluating alloy 82 with increased chromium (Cr) content of 30%, 33% and 36%. Weld joint specimens were prepared by tungsten inert gas (TIG) welding with the prototyped wires of alloy 82 with increased Cr content. The mechanical properties and weldability were investigated using the weld joint specimens. For comparison, conventional alloy 82 and alloy 52M were also tested. The mechanical properties of alloy 82 with increased Cr content were equal to or better than those of the conventional alloy 82. The varestraint test and bending test were carried out to determine the weldability. In the varestraint test, the susceptibility to solidification cracking and ductility-dip cracking was evaluated. The temperature ranges of the ductility-dip cracking of the alloy 82 with increased Cr content was about the same as that of the conventional alloy 82. As a result of these tests, it was confirmed that the alloy 82 with increased Cr content has the same weldability as that of the conventional alloy 82 and was applicable for BWR components.

Keywords

• alloy 82
• alloy 52m
• ductility-dip cracking
• solidification cracking
• varestraint test
• weld joint