Effects of La Element on Oxidation Behavior of MoSi2 Coatings in Wide Temperature Range

MoSi2 coatings were prepared on rare earth La2O3 doped molybdenum alloy substrates by pack cementation method. The effects of La element on the oxidation behavior of MoSi2 coatings in wide temperature range were studied systematically. The results show that the MoSi2 coating exhibits dense microstructure, which is mainly composed of MoSi2 phase. The effects of La element on the oxidation resistance of MoSi2 coating are different at various temperatures. Under the static oxidation conditions at 1600 degrees C, the addition of La element promotes the chemical reactions between the coating and the substrate, and accelerates the consumption rate of MoSi2, which leads to the decrease in the high temperature oxidation resistance of the coating. Meanwhile, La element has little influence on the oxidation resistance of the coating at 800 degrees C. Under the static oxidation conditions at 500 degrees C, La element increases the diffusion rate of Si element in the coating, which favors the formation of a dense oxide layer on the coating surface, and " Pest" effect is inhibited effectively. Therefore, the low temperature oxidation resistance of the coating is improved significantly.