Stress relaxation behavior and dimensional stability of INCONEL® alloy 783

The stress relaxation behavior of a recently developed, low coefficient-of-thermal expansion superalloy, INCONEL® alloy 783,1INCONEL and NIMONIC are trademarks of Special Metals Corporation. been studied in the temperature range from 482 to 649°C and at two different strain levels of 0.1 and 0.2%. These conditions are representative of bolting applications in steam turbines. The initial stress increase, observed at the lower temperatures and stresses, is correlated with dimensional instabilities upon extended exposures at the same temperatures, i.e. the volumetric shrinkage measured in situ in a dilatometer. The experimental results are discussed in the context of creep and transformation strains.