A Comparative Oxidation Study of Mo5Si3 - Mo5SiB2- MoSi2 Three Phase System and a Composite Include Mo Ductile Phase and Intermetallic Compounds

In this study, the increasing oxidation resistance of Mo-Si-B alloys via intermetallic compounds was investigated. For this purpose, the Mo-Si-B bulk samples were fabricated by using mechanical alloying of 33Mo-57Si-10B and 30Mo-47Si-23B (at. %) powder compounds and subsequent sintering under Ar atmosphere at 1200 􀔨 for 3 h. The sintered samples were subjected to oxidation test in 1000 􀔨. Microstructure properties, phase composition of sintered samples and phase composition of oxide surfaces were investigated using scanning electron microscopy, X-ray diffraction and Energy dispersive spectroscopy. The results showed that more oxidation resistance in the 33Mo 57Si-10B alloy was acquired in comparison with 30Mo-47Si-23B alloy. However, this alloy had more pores. The presence of Mo5SiB2 compound in the microstructure of 33Mo-57Si-10B alloy caused formation of borosilicate protective scale. While, Composite microstructure composed of intermetallic compounds/Mo in 30Mo-47Si-23B alloy did not cause formation of oxidation resistance scale. Weight of this alloy was continuously decreased with 0.7mg/cm2h slope to oxidation test end.