HOT CRACKING STUDY OF HIGH CHROMIUM NICKEL-BASE WELD FILLER METAL 52MSS (ERNiCrFe-13) FOR NUCLEAR APPLICATIONS

High chromium nickel-base weld filler metals 52 (ERNiCrFe-7) and 52M (ERNiCrFe-7A) have in recent years replaced filler metal 82 (ERNiCr-3) for new fabrication and for repair applications in commercial nuclear power plants. Filler metals 52 and 52M are selected because they have excellent resistance to primary water stress corrosion cracking (PWSCC). Unfortunately, filler metals 52 and 52M exhibit a higher susceptibility to ductility-dip cracking (DDC) compared to filler metal 82. Filler metal 52MSS (ERNiCrFe-13) is a new high chromium nickel-base alloy with Nb and Mo added to improve resistance to ductility-dip cracking. Increasing Nb has in previous research been shown to widen the solidification temperature range in nickel-base alloys. A wider solidification temperature range can potentially increase susceptibility to hot cracking. This study investigated the solidification behavior and hot cracking susceptibility of three heats of 52MSS and compared the results to a heat of filler metal 52M and a heat of filler metal 52i. The solidification behavior and hot cracking susceptibility were investigated by an optimized Transvarestraint test and by a next generation Cast Pin Tear Test (CPTT). The solidification temperature range and eutectic transformations were measured by a patented Single Sensor Differential Thermal Analysis (SS-DTA) technique. This study showed that filler metal 52MSS was slightly more susceptible to hot cracking than 52M and 52i. This study also demonstrated that the next generation CPTT and SS-DTA technique are effective methods for evaluating the solidification behavior and hot cracking susceptibility of high chromium nickel-base weld filler metals.