INFLUENCE OF TANTALUM AND COBALT ON THE WELDABILITY OF NEW HIGH GAMMA PRIME NICKEL BASED SUPERALLOYS FOR REPAIR AND 3D AM OF TURBINE ENGINE COMPONENTS

Abstract

The propensity of high gamma prime Ni-based superalloys to weld cracking is examined with emphasis on the influence of Ta and Co on weldability. This study focuses on the behavior of LW4280 and LW4280W superalloys containing 16 wt.% Co and 32 wt.% Co respectively. The weldability of experimental compositions of LW4280 with Ta ranging between 0.6 and 6.5 wt.% were also studied. LW4280W alloy, with significantly higher Co fraction, showed a reduced propensity to liquation and stress-strain cracking, improving weldability. However, tensile strength of welds above 982°C (1800°F) was reduced relative to LW4280. The optimal level of Ta in LW4280 was found to be in the middle of the range examined, allowing sound laser DED and GTAW welds to be produced at ambient temperature. Higher or lower levels of Ta resulted in weld cracking produced by GTAW-MA. Possible mechanisms by which Ta and Co levels impact weldability are discussed.