Mechanical Performance of a Non-weldable Ni-Base Superalloy: Inconel 738 Fabricated by Electron Beam Melting

Additive manufacturing processes are becoming increasingly utilized throughout industry. These technologies enable novel design and manufacture of complex components, reduce material waste streams, and potentially reduce development cycles via rapid prototyping. The high-γ′ Ni-base superalloys are of particular interest to the gas turbine engine industry due their high-temperature resistance. However, as a result of the high γ′ volume fraction, these alloys are traditionally termed non-weldable due to a propensity to crack during welding from a host of mechanisms including hot-tearing and strain-age cracking. These mechanisms are subsequently found in fusion-based additive manufacturing processes. Furthermore, there is a long history of employing traditionally processed components in gas turbine engines, and hence, the performance of materials produced by additive manufacturing needs to be closely investigated. In this work is presented the tensile, high-temperature fatigue, and creep deformation behavior for Inconel 738 fabricated through electron beam melting (EBM) additive manufacturing. Under tensile and fatigue conditions, the material was observed to perform in an isotropic manner when tested parallel and transverse to the build direction. Although under creep conditions, the material exhibited an anisotropy between material tested parallel and transverse to the build direction. With the difference attributed to the fine columnar grain structure observed in the additively manufactured Inconel 738. Ultimately, the EBM material was observed to perform comparably to the conventional cast Inconel 738.