Influence of laser wavelength on the powder bed fusion of pure copper

Abstract

In the current work, and for the first time, two 1 kW continuous wave (CW) lasers, with green and infrared (IR) wavelengths, were used to manufacture pure copper with the laser powder bed fusion (LPBF) process. Copper is among the most complex materials to build with LPBF because of its high conductivity and high reflectance under IR irradiation, preventing easy densification. Various aspects were investigated: (1) the stability domain of single LPBF tracks vs (laser power, scan speed) conditions, (2) the porosity rate of 3D samples, (3) the induced microstructures, and (4) the electrical properties of as-built and heat-treated samples. Densification levels of more than 99.5% could be obtained either with an IR Gaussian laser or with green top-hat laser irradiation, but with a wider process parameter window for the green conditions, and higher productivity. The obtained as-built microstructures were mostly columnar and oriented toward the build direction, with a < 110 > main texture. The as-built copper also exhibits a ~ 1015 m−2 dislocation density determined through the X-ray diffraction peak broadening analysis. Finally, up to 95% IACS (international annealed copper standard) electrical conductivities were measured on LPBF test specimens. Such results provide new and useful information on choosing an adequate laser wavelength to optimize the LPBF process on pure copper.