包埋法制备SiC涂层内残留Si的高温抗氧化作用机制

High temperature anti-oxidation mechanism of residual Si in SiC coating prepared by pack cementation

采用包埋法在C/C基体上制备了SiC涂层,借助X射线衍射仪(XRD)和扫描电镜(SEM)对涂层的相组成及微观形貌进行了观察和分析,研究了涂层在1500℃静态空气中的氧化行为,并进一步阐述了涂层的抗氧化机制。结果显示:包埋法制备的涂层由α-SiC、β-SiC及游离Si组成,经XRD半定量分析得到不同工艺制备的涂层中游离Si含量不同;游离Si含量越高涂层越致密;氧化性能显示涂层中适量的游离Si有利于涂层的抗氧化,当涂层中游离Si质量分数为1.3%和2.9%时其抗氧化性能均较好,在1500℃静态空气中氧化7h失重率分别为0.19%和0.16%。

The SiC coating for C/C composite was prepared by pack cementation technique. The phase composition and microstructure of SiC coating was analysed by XRD and SEM. The oxidation behavior of the composites with SiC coating was investigated at 1500℃ in air. The results show that coatings are mainly composed of α-SiC, β-SiC and free Si, and the XRD semi-quantitative analysis shows the content of free Si is different. The coating is more integrity with the higher content of free Si. The oxidation test shows that appropriate amount of free Si of coating can protect C/C composites better. As the residual Si＇s mass fraction is about 1.3% or 2.9%, the anti-oxidation performance of coating are good. The mass-loss of these SiC coated sample is respectively 0.19 % and 0.16 % after oxidation at 1500℃ in air for 7 h.