Development of selective laser melting technology using focused infrared heating

Abstract

Metal additive manufacturing is widely employed in various industry sectors. In conventional power bed fusion, supports that serve as a fastening structure to fix three-dimensional (3D) printed parts to the base plate are fabricated to prevent their movement and/or thermal deformation. However, those supports are difficult or often impossible to remove from the printed part, which does not only reduce the process efficiency but also limits the shape design freedom. In Part A of this thesis, a novel technology that enables support-free, or so called “free-standing”, metal additive manufacturing has been developed. The proposed process combines the solid-state sintering process using focused infrared (IR) heating with the typical laser (liquid-state) sintering process. The IR-sintered body with weak bonding between powder particles acts as a supporting structure, which can be removed easily from the printed part after printing with no post-processing. Successful support-free 3D printing with several metal alloys, including Ti-6Al-4V, was demonstrated. In the second part (Part B), it was also demonstrated that the proposed process could modify/enhance the properties of printed alloy structures because the high-temperature IR heating lowered the temperature gradient around the melt pool significantly. In particular, this study developed a technology that controls the microstructure by changing the temperature gradient and solidification rate through high-temperature IR heating and high-speed scanning.