Laser powder-bed fusion of Mo(Si,Al)2 – Based composite for elevated temperature applications

Abstract Mo(Si,Al)2-based composites are promising candidates to be used as heating elements, high temperature coatings and structural materials. In this work, powders mixture of 90 wt% MoSi2 and 10 wt% AlSi10Mg was subjected to a laser powder-bed fusion (LPBF) to produce Mo(Si,Al)2-based composites. The effect of process parameters on morphological features, phase composition, densification, hardness and oxidation resistance were examined in detail, and the optimal process window was defined. Thermodynamic calculations were performed to supplement the experimental data. The primary phase in the solidified material is the C40 hexagonal Mo(Si1−x,Alx)2 and the solubility of aluminum is governed by the applied volumetric energy density of the laser. The microstructure of the top surface of the samples is composed of fine and coarse cellular Mo(Si1−x,Alx)2, enveloped with Al and Si in inter-cellular regions. The materials exhibit hardness in 800–840 HV1 range depending on process conditions. The LPBF-prepared samples displayed a stable thin oxide layer formation after 120 h of oxidation. The glassy layer of oxides, which predominantly grow from inter-cellular regions, serves as a protective layer for further oxidation. The oxidation rate is two-orders of magnitude slower compared to the reference MoSi2 sample.