Two-dimensional numerical modelling of radiation transfer in powder beds at selective laser melting

The radiation transfer equation is numerically solved in a layer of homogeneous absorbing scattering medium, which is equivalent to the powder bed, irradiated with a normally incident laser beam of an axially symmetric profile to estimate the spatial distribution of the deposited thermal energy. The scattering and lateral transport of laser radiation is shown to decrease the intensity of the heat source at the axis and to produce its weak tail around the laser spot. This decreases the maximum temperature in the powder bed. Narrowing the laser beam to increase the precision of selective laser melting becomes ineffective when the beam radius approaches the extinction length in the powder because it does not adequately narrow the zone of energy deposition.