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

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