超音速等离子体喷涂MoSi2涂层工艺研究

Study on process of supersonic plasma spraying MoSi2 coating

涂层技术是C/C复合材料高温抗氧化与抗烧蚀的有效手段,单一的SiC涂层很难为C/C复合材料提供有效的长寿命保护。金属间化合物MoSi2高温时会形成一层致密的SiO2保护膜,具有特别优异的高温抗氧化性能,常作为C/C复合材料的高温抗氧化涂层。本文采用超音速等离子喷涂法在带SiC涂层的C/C复合材料表面制备了MoSi2涂层,主要研究了喷涂功率、主气(Ar)流量对粉料表面温度、飞行速度、沉积率以及对涂层表面微观结构和结合强度的影响。结果表明:喷涂功率在47.5~52.5 kW之间,既能使粒子有较高的速度和温度,还能保证粉末不过熔,在喷涂功率为50 kW时,粉料的沉积率最高,氧化不高,涂层表面致密性好,截面结合紧密,结合强度高;Ar流量为65 L/min时,能够保证MoSi2粉末有较高的表面温度与较快飞行速度,沉积率最高,氧化不高,涂层表面致密,几乎没有孔隙与裂纹。因此,调控超音速等离子体喷涂工艺参数能够在带SiC涂层的C/C复合材料表面得到致密且结合良好的MoSiO2涂层。

Coating technique is an effective method for protecting C/C composites from oxidation and ablation at high temperature.Single SiC coating hardly provides effective long protection for C/C composites.Intermetallic compound MoSi2 forms a dense SiO2 protective film at high temperature,which has particularly excellent high-temperature oxidation resistance and is often used as high-temperature anti-oxidation coating for C/C composites.MoSi2 coating was prepared by supersonic plasma spray on the surface of SiC-coated C/C composites.Effects of spraying power and primary gas(Ar)flux rate on the temperature,velocity,and deposition rate of the MoSi2 powder,and microstructure and bonding strength of the MoSi2 coating were studied.Results show that in the power range from 47.5 kW to 52.5 kW,the spraying powder could maintain high velocity and temperature,and the powder was not excessive melt.When the power was 50 kW,the spraying powder had the highest deposition rate with less amount of spraying powder oxidized.The as-prepared coating was well compacted,and the sections were closely coupled with high bonding strength.When the primary gas(Ar)flux rate was 65 L/min,the spraying powder with high surface temperature and faster velocity had the highest deposition rate and less amount of oxidation,and the surface of the coating was dense with few pores and cracks.Hence,a dense and well-bonded MoSi2 coating on the surface of SiC-coated C/C composites could be obtained by regulating the parameters of supersonic plasma spraying process.