过去,对铸铁件热浸镀铝再微弧氧化仅有少量的研究,且还存在残留铝影响氧化层性能的问题.为此,对球墨铸铁先热浸镀铝后再微弧氧化形成陶瓷层,采用扫描电镜、能谱分析和X射线衍射分析了陶瓷层的相组成及形貌,并探讨了对陶瓷层进行扩散退火处理的可行性.结果表明:球墨铸铁浸镀铝后微弧氧化获得的陶瓷层主要由α-Al_2O_3相和Υ-Al_2O_3相组成;600℃扩散退火时,因陶瓷层与纯铝层之间热膨胀系数不匹配会导致界面处产生热应力,造成陶瓷层与纯铝层的界面处出现明显孔洞;球墨铸件微弧氧化形成的陶瓷层不适合扩散退火处理:对微弧氧化后,热浸镀铝层剩下多少为佳及处理的问题,应进一步研究.
Ceramic coating was prepared on the surface of ductile iron by hot-dip aluminizing in association with micro-arc oxidation. The phase composition and morphology of the ceramic coating were analyzed by means of scanning electron microscopy,energy-dispersive spectrometry and X-ray diffraction. Moreover,the feasibility to conduct diffusion annealing of the ceramic coating was discussed. Results show that the ceramic coating formed on ductile iron after hot-dip aluminizing and micro-are oxidation is mainly composed of α-Al_2O_3 and Y-Al_2O_3. After being diffusion annealed at 600 ℃, thermal stress and pores were generated at the interface of the hot-dip aluminizing layer and micro-are oxidation ceramic layer because of mismatched thermal expansion coefficient. This means that the micro-are oxidation ceramic coating grown on hot-dip aluminizing layer can not be diffusion annealed, otherwise its microstructure and performances will be destructed.
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