Abstract
Internal frictions (damping capacities or logarithmic decrements) of nickel-based superalloys were measured under various temperatures using the inverted torsion pendulum apparatus. This report presents logarithmic decrements of the polycrystalline Inconel 718 together with those of the single crystal alloy CMSX-4. The temperature dependence of the logarithmic decrements were investigated from room temperature to elevated temperatures (up to 948 K in Inconel 718 and 1223K in CMSX-4). At temperatures below 700 K, logarithmic decrements of Inconel 718 are smaller than those of CMSX-4. However, Inconel 718 is much larger in the logarithmic decrement than CMSX-4 at temperatures above 700-800K. Further, Inconel 718, at temperatures above approximately 600-700K, increases steeply in its logarithmic decrement with the temperature. On the other hand, the logarithmic decrements of CMSX-4 at temperatures less than approximately 1000K scarcely depend on the temperature and increase gradually with the temperature at higher temperatures. It seems that Inconel 718 has a peak in its damping capacity at approximately 920K.
