Creep–Fatigue Interaction Study on Gas Turbine Engine Alloy

Abstract

Alloy IN 718 is used for manufacturing many critical components of gas turbine engine such as compressor blades, discs, and shafts. During engine operation, these components are subjected to cyclic loading along with steady-state operation at high temperatures. These operating conditions induce damage resulting from interaction of creep and fatigue. In order to predict realistically the life of these components, it is necessary to understand creep–fatigue interaction mechanisms and important to carry out test at conditions simulating engine parameters. Therefore, isothermal LCF tests with and without hold time were conducted at a temperature of 600 °C, strain rate of 10−3 s−1 and total strain amplitude varying from 0.4 to 0.6%. Hold time of 1 and 5 min was inserted at maximum strain amplitude to give tensile dwell condition. In gas turbine engine, the presence of centrifugal force of rotating components leads to sustained tensile load in addition to varying loads; therefore, it was decided to have dwell time at peak tensile strains. The investigation revealed that the fatigue life was adversely affected when hold time was introduced at peak strain. The effect on fatigue life with 1- and 5-min hold is discussed. Deformation mechanism of tested samples was also studied using SEM.