Evaluation of weld metal 82 and weld metal 152 stress corrosion cracking susceptibility

Welds are often an area of concern in steam generators (SG) because of the different materials in the welds, the residual stresses which result from the welding process and subsequent operational stresses. In general a weld is composed of a base metal, weld metal and the heat affected zone (HAZ). This study investigated the corrosion performance of welds connecting the divider plate to the weld buildup in a welded-in divider plate (WIDP) design. The materials of interest were Alloy 690 plate, Weld Metals (WM) 82 and WM 152. Weld test samples were fabricated in a manner that is consistent with SG fabrication practices in which WM 152 is used to attach the Alloy 690 plate to the WM 82 weld buildup. Round tensile specimens were used to evaluate WIDP welds. Specimens were manufactured parallel to the weld fusion lines, hence, the gauge length of each specimen contained either the base metal or a metal and a HAZ. Use of specimens of this orientation permitted evaluation of all the materials contained in the specimen for stress corrosion cracking (SCC) susceptibility, not just the weakest materials. Constant extension rate tests were performed in Pressurized Water Reactor (PWR) primary water chemistry and faulted primary water chemistry at 343 C and a strain rate of 1 x 10-6 sec-1. No SCC was found in any specimen in either environment