  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. This paper presents the design and validation of high pressure laser
melting (HPLM) testbed; this 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 pressure effects on processing of common
L-PBF materials, and can be applied in the future to materials that are
challenging to process under ambient pressure, such as those with high vapor
pressures.
