Effect of Defects and Inclusions on High Cycle Fatigue Fracture of Inconel 718 Fabricated by Selective Laser Melting

Abstract

Inconel 718, a kind of Ni-based superalloy, shows high mechanical properties even in high temperatures up to 700℃. However, Inconel 718 causes severe wear of machining tools because it is a difficult-to-cut material. Fabricating Inconel 718 by using selective laser melting, a kind of additive manufacturing, is therefore expected as the most promising way to deal with this problem. Fatigue properties of parts fabricated by selective laser melting are inferior to parts fabricated by conventional ways. Revealing the fatigue fracture is necessary to improve fatigue properties. In this study, fatigue test was conducted with Inconel 718 fabricated by selective laser melting and the fatigue fracture surface was observed. Fatigue fracture origins shifted from the surface of specimensto the internal part of specimens by hot isostatic pressing. In specimens with hot isostatic pressing, TiN inclusions were found in fatigue fracture origins. To raise fatigue properties of parts fabricated by selective laser melting needs to remove these TiN inclusions.