La元素对MoSi_(2)涂层的宽温域氧化行为影响

Effects of La Element on Oxidation Behavior of MoSi_(2) Coatings in Wide Temperature Range

采用包渗法在稀土La2O3掺杂钼合金基体上制备MoSi2涂层,并就La元素对MoSi2涂层宽温域氧化行为的影响机制进行了系统研究。结果表明:钼镧合金基MoSi2涂层组织结构较为致密,主要物相为MoSi2相。不同温度下La元素对MoSi2涂层的抗氧化性能的影响不同,1600℃高温静态氧化条件下,La元素的存在促进了涂层与基体的化学反应,加剧了MoSi2抗氧化主体层的消耗速度,使得MoSi2涂层的高温抗氧化性能有所下降;800℃中温静态氧化条件下,La元素对MoSi2涂层抗氧化性能影响不明显;500℃低温静态氧化条件下,La元素的加入加速了涂层中Si元素的扩散,使得涂层表面能较快形成一层致密的氧化层,"Pest"效应得到抑制,从而显著提升涂层的低温抗氧化性能。

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℃,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℃.Under the static oxidation conditions at 500℃,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.