CVD沉积工艺对SiC涂层结晶度与耐腐蚀性能的影响

EFFECT OF CVD DEPOSITION PROCESS ON CRYSTALLINITY AND CORROSION RESISTANCE OF SiC COATINGS

通过化学气相沉积(CVD)SiC涂层来提高SiC_(f)/SiC复合材料的耐腐蚀性能,本文以CH_(3)SiCl_(3)(MTS)为源气体,在反应烧结SiC基体上制备SiC涂层,控制沉积温度、炉压及H_(2)/MTS摩尔比等工艺参数,通过X射线衍射实验(XRD)得到不同工艺条件下生成的碳化硅涂层的物相组成和结晶度,通过高温水腐蚀实验检测涂层的耐腐蚀性,并利用扫描电子显微镜(SEM)观察腐蚀前后的表面形貌。结果表明:当沉积时间为8 h,沉积温度从1050℃到1250℃,β-SiC涂层表面平整性提高,沉积厚度由12.97μm急剧增加至71.10μm,SiC晶粒尺寸逐渐增大,最终呈金字塔状;碳化硅涂层腐蚀60 d后,表面呈现针状结构,1250℃下沉积的SiC涂层耐腐蚀性能较好;β-SiC涂层的晶粒尺寸随沉积炉压的增大而增大,结晶度随沉积炉压增大而减小,在200 Pa以下,获得的β-SiC晶粒的结晶度最高(81.08%)、晶粒尺寸最小(13.7 nm);随着H_(2)/MTS摩尔比增加,β-SiC晶粒结晶度迅速下降,当H_(2)/MTS=6.5时,结晶度最高(95.91%)。

The corrosion resistance of SiC_(f)/SiC composites was improved by chemical vapor deposition(CVD)SiC coatings.In this paper,SiC coatings are prepared on reaction sintering SiC matrix with CH_(3)SiCl_(3)(MTS)as the source gas.Surface morphology and corrosion resistance of silicon carbide coatings were related with parameters in CVD such as deposition temperature,furnace pressure and mole ratio of H_(2) and MTS.The phase composition and crystallinity of silicon carbide coating under different process conditions were obtained by X-ray diffraction experi-ment(XRD).The corrosion resistance of the coating was detected by high-temperature water corrosion experiment,and the surface morphology before and after the corrosion was observed by scanning electron microscope(SEM).The results showed that when the deposition time was 8 hours and the deposition temperature was from 1050℃to 1250℃,the surface roughness of SiC coating was improved,the deposition thickness increased sharply from 12.97μm to 71.10μm,and the grain size of SiC gradually increased and finally presented a pyramid shape.After 60 days of corrosion of silicon carbide coating,the surface presents an acicular structure.The SiC coating deposited at 1250℃had better corrosion resistance.With the increase of deposition furnace pressure,the crystallinity ofβ-SiC grains decreased sharply and the grain size increased sharply.The crystallinity ofβ-SiC was the highest(81.08%)and the grain size was smallest(13.7 nm)under 200 Pa.The crystallinity ofβ-SiC grain decreased sharply with the in-crease of the molar ratio of H_(2) and MTS.When the molar ratio of H_(2) and MTS was 6.5,the crystallinity reached its highest point(95.91%).