Processing challenges in additively manufactured single crystal alloys: a process–structure–property relationship approach

Abstract

The single-crystal (SX), formulated from nickel-based compositions and extensively employed in aero engine turbine blades, demonstrates exceptionally higher-temperature properties such as creep, fatigue performance, and resistance to corrosion attack than its equivalent materials like equiaxed conventional cast (CC) or columnar directionally solidified (DS). Therefore, the research interest in advanced nickel-based superalloys particularly suited for the SX requirement has become a focus for aerospace industries. Hence, the chemical formulation of the SX systems has been constantly pursued to enhance the elevated temperature properties for superior performance. Therefore noteworthy chemical compositions were incorporated from first-generation SX superalloys such as CMSX-2 to second-generation SC superalloys such as CMSX-4 and René N5 with 3wt.% of rhenium (Re) targeted for domestic and army engines. Currently, SX superalloys are manufactured by cast route, which involves an expensive molten metal melting system and solidification setup to produce sound, high-quality cast parts like as-cast high-pressure turbine blades. In recent times, metal additive manufacturing (AM) has had great significance in manufacturing intricate and complex geometrical near net-shaped parts without tooling and molding applications. The laser powder deposition (LPD) is an AM technology capable of manufacturing end-used parts from metal powder irradiated by laser source. Therefore, LPD capabilities have been exploited to manufacture the CMSX-4 SX superalloys and have shown promising functional performance. © 2023 Elsevier Inc. All rights reserved.