Evaluation of molybdenum-based silicides in a combustion and endothermic environment

摘要

Molybdenum-based silicides are being considered for potential high temperature applications due to their high melting points, improved oxidation resistance and high temperature creep strength. Of the molybdenum-silicon compounds, molybdenum disilicide (MoSi_2) has been characterized the most due to its excellent oxidation resistance at temperatures up to 1800°C in air and its proven performance as an industrial heating element. Pentamolybdenum trisilicide (Mo_5Si_3) is also being investigated for high temperature applications due to its improved creep resistance although its oxidation resistance has been shown to be unacceptable for high temperature use in air. Additions of boron to Mo_5Si_3 can improve its oxidation resistance [1,2]. To better understand the stability of molybdenum-based silicides an investigation was performed in a industrial combustion and heat-treating environment to compare the performance of plasma sprayed coatings of MoSi_2 and Mo_5Si_3 to hot pressed MoSi_2 and MoSi_2-based composites. The oxidation behavior of plasma sprayed Mo_5Si_3 was investigated to provide a comparison to plasma sprayed MoSi_2 which typically contains a discontinuous dispersion of Mo_5Si_3 as a result of silicon loss during the high temperature plasma spray operation.