Characterization of Carbide Dispersions in Molybdenum Deposits by Laser Powder Bed Fusion

In this paper, we report coupled optical and electron microscopy methods that readily enable quantification of dispersions and their effects on solidification cracking for a laser powder bed fusion deposit of Mo with various concentrations of ZrC particles. Through a jet-polishing procedure, the carbide particles were dislodged allowing pin holes to form in the microstructure that created high contrast features for particle size and distribution quantification. Coupled with this was the use of electron backscattering to identify microstructural defects, including micro-cracks. Through image analysis, the carbide dispersion reduced the anisotropic directional distribution of these linear defects which is explained by the change in the deposited grain size and morphology that accompanies the carbide inclusion. These results highlight how complementary sample preparation methods and imaging can provide a sufficient field-of-view for understanding small-scale features within additive manufactured builds.