Experimental analysis and simulation of the melt pool behaviour in laser powder bed fusion of pure tungsten

The processing parameters used in additive manufacturing directly affect the final properties of the product. This study has used single-track formations to study how parameters affect localised regions of molten tungsten when selectively melting pure tungsten powder. A sequence of individual track experiments was performed and the results compared to numerical simulations using OpenFOAMTM. Tungsten melt tracks were produced using laser focus offsets of 0 and 1 mm, corresponding to beam diameters of 50 and 43 μm at the surface, respectively. The beam diameter is defined by the radial distance from the centre of the beam where the intensity has dropped to 0.135 of peak intensity. 200W laser power was used during experiments and simulation. The laser was scanned at 50, 138, 225, 313 and 400 mm/s, resulting in different melt formations. The laser energy densities correlated with the experimental melt widths ranging from 89 to 208 µm and with simulated melt volume fractions ranging from 0.39 and 0.79. Comparisons of the experimental and simulation results yielded correlation coefficients (R2) values ranging from 0.958 to 0.988. The numerical model was assessed and its suitability for tungsten laser melting discussed.