Microstructural development and creep behavior in A286 superalloy

The precipitation-hardened alloy A286 has been characterized as a function of ageing treatment, and the creep behavior has been studied in the temperature range of 600-700 degreesC and at 230-740 MPa. Microhardness tests of samples aged at different temperatures have been performed, and it was observed that the fastest precipitation kinetics of the metastable gamma occurred during ageing at 730 degreesC. Further exposure at this temperature degraded the good mechanical properties of the material because the gamma dissolved, and the stable eta phase formed. Optical and scanning and transmission electron microscopy (SEM and TEM, respectively) characterization of samples in as received state and after ageing were performed to study the microstructural development. In all creep tests, the damage observed was intergranular. The correlation between secondary strain rate and time to failure was shown to be a modified Monkman-Grant, including the elongation to rupture and an exponent different of 1 for the strain rate to obtain a better correlation. T he Larson-Miller parameter has been used to correlate creep stress, temperature and rupture time for the aged material. (C) 2004 Elsevier Inc. All rights reserved.