等离子喷涂及真空热处理过程中MoSi_2涂层的相演变

Phases evolution of molybnenum silicide coating in plasma spraying and heat treatment process

分别采用MoSi2,Mo-66.7%Si和Mo-70%Si(摩尔分数)粉末为原料,在45钢上大气等离子喷涂MoSi2涂层,对喷涂前后相以及真空热处理对涂层相和组织的影响进行了研究。结果表明,以MoSi2为原料喷涂后,涂层主要是由MoSi2和Mo5Si3相组成,MoSi2由亚稳定的MoSi2(h)六方结构和稳定的MoSi2(t)四方晶体结构组成。而Mo-66.7%Si和Mo-70%Si两种粉末喷涂后,涂层均由Mo,Si单质粉组成,喷涂过程没有形成硅化物。Mo-66.7%Si涂层在1050,1200℃热处理1h后,涂层中主相是Mo5Si3,次相为MoSi2。Mo-70%Si涂层在800,1 000℃热处理30min后,生成了少量的MoSi2,Mo5Si3和Mo3Si。在1 050℃热处理时,随着时间的延长,MoSi2相含量相对增多,当热处理时间为30,45min时,由于Mo,Si和Fe之间的反应扩散,还生成了FeMoSi和Fe3Si相。

Silicide molybdenum coating was deposited on 45 steel sbustrate with MoSi2, Mo-66.7mol%Si and Mo-70 mol%Si by air plasma spraying and vacuum heat treatment. The influence of air plasma spraying and vacuum heat treatment on phase and structure evolution were studied. The results show that the phase of the coating is MoSi2 and Mo5Si3 sprayed with MoSi2 as raw material powder. The MoSi2 phase were made of metastable MoSi2(h) and steady MoSi2(t). However, the phases of coatings are made of simple Mo and Si phases sprayed with Mo-66.7mol%Si and Mo-70mol%Si as powder respectively. The silicide molybdenum coating was not formed during plasma spraying process. The major phase is Mo5Si3 and minor phase is MoSi2 after vacuum heat treatment at 1 050 ℃ and 1 200 ℃ for 1 h. Mo-70mol%Si coating formed a small amount of MoSi2, Mo5Si3 and Mo3Si phases treated at 1 050 ℃ and 1 200 ℃ for 30 min. At 1 050 ℃, with the increasing time,the relative content of MoSi2 gradually increased. The diffusion reaction among Mo, Si and Fe formed FeMoSi and Fe3Si phases with heat treatmeat for 30 or 45 min.