Analysis of microstructure and mechanical properties in alloy 690 weldments using filler metals I-82 and I-52

This work investigated the weldability and mechanical properties of weldmen ts made with Inconel filler metals I-52 and I-82 in the welding of Inconel alloy 690. Gas tungsten are welding was used with different multipass seque nces. The microstructures of the fusion and heat affected zones were examin ed and weldment properties were compared by tensile, hardness, and impact t ests. Fracture surfaces were examined by scanning electron microscopy. Expe riment results indicate that the subgrain structure near the fusion zone ce ntreline was dominated be equiaxed dendrites in I-82 weldments hilt by colu mnar dendrites in I-52 weldments. In addition, the 1-82 weldments had a fin er subgrain structure near the fusion zone centreline and smaller cellular spacing near the fusion line than I-52 weldments. Mechanical test results d emonstrate that the I-82 weldments had higher tensile strength (622-630 MPa ) with rupture occurring in the base metal. In comparison, the I-52 weldmen ts had lower tensile strength (565-578 MPa) and rupture occurred in the fus ion zone. Filler metal I-52 showed better welding performance and greater i mpact toughness with only slight sensitivity to the number Of passes. Howev er, a gradual increase in the hardness of the weld was observed as the numb er of passes increased.