Parametric Study on In Situ Laser Powder Bed Fusion of Mo(Si_1-x,Al_x)₂

Mo(Si_1-x,Al_x)₂ composites were produced by a pulsed laser reactive selective laser melting of MoSi₂ and 30 wt.% AlSi10Mg powder mixture. The parametric study, altering the laser power between 100 and 300 W and scan speed between 400 and 1500 mm·s^-1, has been conducted to estimate the effect of processing parameters on printed coupon samples' quality. It was shown that samples prepared at 150-200 W laser power and 400-500 mm·s^-1 scan speed, as well as 250 W laser power along with 700 mm·s^-1 scan speed, provide a relatively good surface finish with 6.5 ± 0.5 µm-10.3 ± 0.8 µm roughness at the top of coupons, and 9.3 ± 0.7 µm-13.2 ± 1.1 µm side surface roughness in addition to a remarkable chemical and microstructural homogeneity. An increase in the laser power and a decrease in the scan speed led to an apparent improvement in the densification behavior resulting in printed coupons of up to 99.8% relative density and hardness of ~600 HV1 or ~560 HV5. The printed parts are composed of epitaxially grown columnar dendritic melt pool cores and coarser dendrites beyond the morphological transition zone in overlapped regions. An increase in the scanning speed at a fixed laser power and a decrease in the power at a fixed scan speed prohibited the complete single displacement reaction between MoSi₂ and aluminum, leading to unreacted MoSi₂ and Al lean hexagonal Mo(Si_1-x,Al_x)₂ phase.