Low Cycle Fatigue Response of Additive Manufactured Advanced Structural Alloys: Insights into High Performance Alloy Fatigue Life

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Abstract
Additive Manufacturing enables the production of intricate geometries and products with improved strength-to-weight ratios, driving its applications in defence, aerospace, and automobile sectors. Maraging steel and Superalloy Inconel 625 are renowned for their excellent mechanical properties and are candidate materials for high performance applications. It is essential to study the fatigue behaviour of additively manufactured samples prior to their deployment in real working environments, as their mechanical properties and fatigue behaviour differ from those of conventionally manufactured materials. In the present study, low cycle fatigue (LCF) behaviour of Maraging steel (M300) and Inconel 625, at different strain amplitudes and heat treatment conditions were evaluated. Fractographic characterization was conducted using scanning electron microscopy (SEM). To understand the effect of build orientation on LCF behaviour, the maraging steel samples were also tested in different build orientations (0 o and 90 o ). It was found that build orientation significantly affected the fatigue life of additive manufactured maraging steel samples. The LCF study was also done at different strain amplitudes for Inconel 625 and results indicated that there was drastic decrease in fatigue life at higher strain amplitudes. It was observed that defects introduced due to layer wise processing of additive samples have adverse effect on fatigue life. Ultrasonic shot peening was also applied to the additively manufactured fatigue samples to examine its impact on fatigue life.