Superior high-temperature mechanical properties of crack-free IN738LC superalloy additively manufactured by L-DED via novel self-adjustable baseplate optimization

• Self-adjustable baseplate enables crack-free L-DED of relatively large IN738LC. • In-situ stress regulation converts tensile stresses into compressive states. • Enhanced thermal accumulation promotes in-situ γ′ precipitation (68.68 vol%). • As-built IN738LC exhibits exceptional room- and high-temperature properties. Ni-based superalloy IN738LC is critical for hot-section components of gas turbines and aeroengines due to its high-temperature strength and oxidation resistance, yet its laser directed energy deposition (L-DED) is limited by intrinsic cracking susceptibility. This work introduces a self-adjustable baseplate with movable tenons enabling crack-free L-DED of relatively large IN738LC single-wall builds. Thermo-mechanical simulations show that tenon motion regulates interfacial stress, converting tensile stresses into compressive ones during deposition. Concurrently, the self-adjustable baseplate promotes thermal accumulation, driving in-situ γ′ precipitation, coarsening, and refined distribution. The resulting as-built IN738LC exhibits exceptional high-temperature mechanical performance, with ultimate tensile strengths of 948 MPa at 800 °C, 628 MPa at 900 °C, and 361 MPa at 1000 °C, and corresponding elongations of 18%, 24%, and 21%. These values exceed previously reported data for conventionally processed or additively manufactured IN738LC and constitute the first reliable high-temperature tensile dataset for L-DED IN738LC. Standard post-deposition heat treatment yields a bimodal γ′ morphology with modest ductility improvement. This study provides a process-integrated stress-mitigation strategy combining adaptive mechanical constraint and thermal regulation, offering a practical approach to the direct fabrication of high-performance non-weldable Ni-based superalloys.