Abstract
Mo(Si1−x,Alx)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(Si1−x,Alx)2 phase.
Highlights
The research interests for metal silicides have continuously revolved around the development of a composite material with sufficient operating temperatures thresholds employable in applications across the lucrative aerospace and energy production sectors [1]
In our previous work [28], we reported the in situ preparation of Mo(Si,Al)2 -based composite bulks by selective laser melting of a MoSi2 -30 wt.% AlSi10Mg powder mixture covering the powder characteristics, printability, and phase composition of the produced bulks
It was shown that the samples produced at 150–200 W laser power and 400–500 mm·s−1 scanning speed, as well as at 250 W laser power and 700 mm·s−1 scanning speed, possess an admissible surface finish and the notable chemical and microstructural homogeneity
Summary
The research interests for metal silicides have continuously revolved around the development of a composite material with sufficient operating temperatures thresholds employable in applications across the lucrative aerospace and energy production sectors [1]. MoSi2 is an attractive transition metal silicide for structural applications at elevated temperatures as it possesses an outstanding oxidation resistance up to 1700 ◦ C [2], increasing with temperature electrical resistivity, which makes the material to be considered as a promising heating element [3]. Aluminum is one of the alloying elements negating the pest oxidation of MoSi2 through the formation of alumina (or mullite) due to the development of the Mo(Si,Al) compound [8,9,10]. Mo(Si,Al) composites into bulks is a challenging task with the conventional press and/or sintering methods; additive manufacturing techniques, which offer flexible fabrication, are prone to overcome many obstacles.
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