An assessment of the mechanical characteristics and optimum welding condition of Ni-based super alloy

Abstract

In this study, the TIG welding process for the super alloy (Alloy 617), which is a heat- and corrosion-resistant material, was optimized. The mechanical properties of the weld of Alloy 617 also were assessed on the basis of reliability. The results yield following conclusions: 1) it is effective to use Ar+2.6%H2 gas as a shield gas for the TIG welding of Alloy 617(base metal)+Tissen 617 (filler metal). 2) when welding under the optimized welding condition, the base metal and the HAZ do not show large differences in the metallurgicalmicro-structure and composition but the weld metal zone does show coarse grain compared to the base metal and HAZ. 3) the yield strength ratio of weld/base metal is 0.96, the tensile strength ration is 0.89 at R.T, the yield strength ratio is 0.71, and the tensile strength ratio is 0.86 at 700oC. 4) the bending strength ratio of the weld at 700oC/R.T is assessed to be 0.89.