A testbed for investigation of laser powder bed fusion at elevated atmospheric pressure

Abstract

Metal additive manufacturing (AM) by laser powder bed fusion ( L -PBF) builds upon fundamentals established in the field of laser welding which include the influence of gas and plume dynamics on weld depth and quality. L -PBF demands a thorough investigation of the complex thermophysical phenomena that occur where the laser interacts with the metal powder bed. In particular, melt pool turbulence and evaporation are influenced by the ambient gas chemistry and pressure, yet typical L-PBF equipment lacks flexibility to alter the ambient pressure within the process chamber. This paper presents the design and validation of high pressure laser melting (HPLM) testbed. This system accommodates bare metal plate samples as well as manually-coated single powder layers, and operates at up to 300 psig. The open architecture of this testbed allows for full control of all relevant laser parameters in addition to ambient gas pressure and gas flow over the build area. Representative melt tracks and rasters on bare plate and powder are examined in order to validate system performance, and preliminary analysis concludes that pressure has a significant impact on melt pool aspect ratio. The HPLM system thus enables careful study of the effects of pressure on the outcomes of the L-PBF process, and can be applied in the future to materials that are challenging to process by L-PBF under ambient pressure, such as those with high vapor pressures.