Microstructural control and mechanical property enhancement of laser melting deposited inconel 718Plus thin-walls via a hybrid strategy of substrate cooling and gradually decreasing laser power

Laser Melting Deposition (LMD) offers high material utilization, near-net shaping capabilities, and excellent process flexibility, making it promising for additive manufacturing of nickel-based superalloys. Thermal accumulation during deposition causes grain coarsening, texture enhancement, and mechanical anisotropy, limiting its engineering applications. To address these issues, this study proposes a hybrid strategy of substrate cooling and gradually decreasing laser power (CDP), systematically investigating its influence on the microstructure and mechanical properties of Inconel 718Plus alloy thin-walls. The CDP strategy reduces thermal accumulation, increases cooling rates, and suppresses columnar grain growth. Results show that the texture is weakened, yielding an equiaxed grain structure with an average size from 84.1 μm to 98.4 μm. Compared to the uniform laser power strategy, the CDP approach enhances the tensile strength in the top region to 1100 MPa and the yield strength to 731 MPa, representing increases of 38.9 % and 48.9 %. Simultaneously, it also facilitates the uniform dispersion of Laves phases, significantly enhancing hardness and wear resistance. The study demonstrates that the CDP strategy offers substantial advantages in microstructural regulation, texture suppression, and second-phase distribution optimization, while simultaneously enhancing mechanical properties. These improvements provided valuable process guidelines for microstructure tailoring and performance optimization of high-performance LMD alloy components.