Answer
'Spring Temper' Inconel X-750 achieves its strength primarily through cold work, which provides very high static load capacity but lower thermal stability and potentially lower fatigue life due to the high density of internal defects and residual stresses. 'No. 1 Temper' involves a solution heat treatment at approximately 1150°C followed by a double-aging cycle. This process produces a more stable microstructure with optimized grain size and discrete $\gamma'$ precipitation. For high-cycle fatigue, the No. 1 Temper provides better resistance to crack initiation. While the ultimate tensile strength (UTS) might be lower than spring temper, the endurance limit and stability at temperature are superior, which is critical for wave springs used in aerospace seals.
