POSTWELD SOLUTION ANNEALING EFFECTS ON THE DUCTILITY OF NI-CO-CR-BASEALLOY GAS TUNGSTEN ARC WELDS

The welding characteristics of a commercial wrought alloy with a nomin al composition of Ni-29Co-28Cr-2.75Si were investigated. Gas tungsten are weldments with filler metal matching the chemistry of the alloy we re found to have limited room-temperature ductility in the as-welded c ondition. Since welding is the main fabrication method of this alloy t he welding and postweld heat treatment (PWHT) characteristics were exa mined to provide guidelines for fabrication in the field. Metallograph ic evaluation revealed that the weld metal was characterized by the di stribution of a continuous eutectic phase consisting primarily of (Si, Ti)(x)Ni-y. The continuous eutectic phase in the as-welded deposit, wh ich caused poor ductility of the welds, was successfully reduced or re moved with proper PWHT. The PWHT is necessary if cold forming of a wel dment is required after welding or if adequate joint ductility is a de sign requirement. The recommended PWHT temperature is 1050 degrees C.