Thermo mechanical fatigue life prediction of Ni-based superalloy IN738LC

Abstract

The thermo mechanical fatigue (TMF) test is known to most accurately simulate the operational environment of a gas turbine’s substate. However, because the TMF test equipment and methodology are very complex, these tests are difficult to conduct. Some researchers have recently attempted to examine methods for evaluating the TMF lifetime of superalloy materials used in turbine blades by using the results of a low cycle fatigue (LCF) test in which the test equipment and method are relatively simple. However, this research was mainly conducted on specific materials such as M963 and GTD-111, and only a few studies have been conducted on IN738LC, which is a widely used material for commercial gas turbine blades. Therefore, this study examined a method for evaluating the TMF lifetime of an IN738LC material by using LCF rtest results. For that purpose, LCF and TMF tests were conducted, and the TMF lifetime was predicted with the LCF test results, using the Ostergren and Zamrik models. Lifetime prediction of IN738LC using the LCF test results from this study was compared with previous lifetime prediction results on other superalloys such as M963 and GTD-111 to review the cause of the difference in lifetime prediction results.