STUDIES ON CREEP STRESS RUPTURE BEHAVIOR OF SUPERALLOY 718 WELDMENTS USED IN GAS-TURBINE APPLICATIONS

Superalloy 718 in the solution-treated condition was welded autogenously by electron beam welding and gas tungsten arc welding processes. The weldments after suitable heat treatment were subjected to creep/stress rupture testing at 650-degrees-C and 690 MPa. The results showed that the Laves phase resulting in the weld metal is detrimental to the creep rupture life of weld metals when present with the continuous morphology found in gas tungsten arc welds. The lower amounts and discontinuous morphology of the Laves phase in electron beam weldments in combination with favourable grain orientation resulted in relatively better rupture properties for these weldments.