Investigation on the Role of Hot Isostatic Pressure in Tailoring Residual Stresses of Selective Laser Melted Inconel 718 Alloy

Inconel 718 exhibits excellent mechanical properties and superior high-temperature performance, making it a preferred material in aerospace and energy sectors. Selective Laser Melting (SLM) offers superior densification and design flexibility, enabling near-net-shape fabrication of complex Inconel 718 components but also introduces significant residual stresses due to rapid thermal cycles and steep temperature gradients. Hot Isostatic Pressing (HIP) is widely employed to enhance microstructure and eliminate internal defects in SLM parts, yet its effect on residual stress evolution remains insufficiently understood. This study integrates finite element simulations with indentation-based experimental validation to investigate residual stress evolution in SLM-processed Inconel 718 components in both as-built and HIP-treated states. Subsequently, the effects of varying HIP parameters are analyzed to determine optimal post-processing conditions. Results confirm that the SLM process induces highly anisotropic residual stresses with localized concentrations, which can be alleviated and effectively homogenized by HIP. Specifically, increasing isostatic pressure primarily drives plastic flow and omnidirectional stress relaxation. By contrast, varying the temperature within 800-1175 °C (at 160 MPa) plays a subtler role, primarily attenuating spatial gradients with only limited impact on overall magnitudes, while the longitudinal component maintains a persistent tensile dominance. Furthermore, substrate removal promotes residual stress redistribution, particularly at the wall-substrate junction, though longitudinal tensile stress moderately increases due to axial contraction. These findings provide validated insights into how HIP parameters reshape stress anisotropy, offering practical guidance for enhancing the reliability of SLM Inconel 718 components. • SLM induces highly anisotropic and uneven residual stress fields. • HIP at 1175 °C/160 MPa eliminates stress concentrations via plastic flow. • HIP pressure dominates magnitude reduction; temperature promotes stress uniformity. • Substrate removal prior to HIP mitigates constraint-induced stress concentrations.