Oxidation and Ablation Behaviors of Mo-Si-B Alloys and Mo-Si-B-Ag Alloys

Since Mo based alloys exhibit superior mechanical properties at high temperatures and have a high melting point of similar to 2500 degrees C, many studies have been carried out in order to use the alloy system in high temperature applications. Especially, since the Mo rich area in Mo-Si-B system shows a thermodynamic equilibrium of ductile Mo (solid solution) and a ternary phase (Mo5SiB2), the alloy system is a potential material for high temperature applications. In the current study, Mo-Si-B alloys and Mo-Si-B-Ag alloys have been investigated. The fabricated alloys were oxidized via heating with laboratory furnace at 800, 1100 and 1300 degrees C in air. At the same time, ablation tests were performed using a gas torch with a mixture of LPG and oxygen. When 5 at% of Ag was added to the alloy, the alloy exhibited an enhanced oxidation resistance, but the flame ablation resistance did not show a significant difference. The oxidation mechanism for the alloy systems with and without Ag additions are discussed in terms of microstructural observations and weight changes.