Near-infrared laser powder bed fusion of pure copper: Post-processing and structure–property relationships

Growing demand for performance-optimized copper components has increased interest in additive manufacturing (AM) to realize complex geometries and internal architectures. Among AM processes, laser powder bed fusion (LPBF) enables fabrication of pure copper. However, with near-infrared (NIR) lasers it suffers from low absorptivity and high thermal conductivity that promote lack-of-fusion (LOF) porosity. In this study, pure-copper coupons were fabricated on an EOS M280 using a design of experiments that varied scan speed, laser power, and hatch spacing at a fixed layer thickness. Post-processing comprised heat treatment (HT, 950 °C, 120 min) and hot isostatic pressing (HIP, 950 °C, 100 MPa, 120 min). Process–structure–property relationships were established through density and electrical conductivity measurements, tensile testing, X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS), and electron backscatter diffraction (EBSD). Scan speed emerged as the dominant parameter governing porosity. HIP increased density only when the as-printed density was already high. XRD indicated single-phase Cu under all conditions, while EBSD showed that post-processing drives recrystallization, grain coarsening, and abundant twins. EDS maps revealed oxygen that appeared diffuse in as-printed material becoming concentrated at residual pore walls after HIP. These microstructural changes reduce electron scattering and enhance ductility. Conductivity increased monotonically from LPBF to LPBF+HT to LPBF+HIP, while ultimate tensile strength (UTS) decreased as expected from Hall–Petch softening. The results provide practical guidance for achieving higher-quality copper on widely available NIR-LPBF systems using standard powders and targeted post-processing.