Effect of Long-Term Exposure on Microstructure and Hardness of Aged Haynes 282 Alloy

Nickel-based superalloy, Haynes 282, is a promising material for aero and land-based gas turbine applications and advanced ultra-supercritical (AUSC) steam power plants due to its outstanding combination of high thermal stability, high-temperature strength; excellent fatigue, creep and oxidation resistance; remarkable fabricability and weldability. Despite its several budding attributes, the alloy needs further developmental activities to realize material challenges for AUSC applications. In the present study, an attempt was made to investigate the influence of long-term exposure of this alloy at AUSC power plant operating temperature on microstructure and hardness. The alloy was subjected to two-step aging and followed by long-term exposure at 760 °C up to 2000 h. The alloy was also put through single-step aging for comparison purpose. The microstructural characterization of the alloy reveals major phases γ , γ ', M 23 C 6 and M 6 C in single-step and two-step aging and in long-term exposure conditions without any deleterious phases, viz. μ , η , σ phases. The morphology of γ ' precipitate and its volume fraction was evaluated by using electron microscope images. Vickers hardness of the alloy increased from 334 ± 3 HV 10 in two-step aged condition to 372 ± 2 HV 10 upon exposure to 250 h and dropped to 360 ± 2 HV 10 at 500 h and thereafter saturated.