THERMAL-STRESS DEVELOPMENT IN A NICKEL-BASED SUPERALLOY DURING WELDABILITY TEST

A finite element model has been developed to quantitatively evaluate t he local thermomechanical conditions for weld metal solidification cra cking in a laboratory weldability test (the Sigmajig test). The loadin g mechanism in the Sigmajig test was simulated by means of nonlinear s pring elements. The effects of weld pool solidification on the thermal and mechanical behaviors of the specimen were considered. An efficien t algorithm was developed to include the solidification effects in the material constitutive relations. Stress/temperature/location diagrams were constructed to reveal the local stress development behind the tr aveling weld pool where solidification cracking occurs. Based on the c oncept of the material resistance to cracking and the mechanical drivi ng force for cracking, the calculated local stress in the solidificati on temperature range was used to explain the experimentally observed c racking initiation behaviors of a nickel-based superalloy single cryst al under different welding and loading conditions.