热处理对聚苯酯铝硅封严涂层硬度的影响

Effect of Heat Treatment on Hardness of AlSi-Polyphenylester Seal Coating

研究了聚苯酯铝硅封严涂层硬度随温度的变化规律及其微观机理。采用显微维氏硬度计对涂层进行硬度测试;通过扫描电镜及能谱分析,研究了Si、Al等元素在基体、Ni5Al过渡层及聚苯酯铝硅涂层内的分布变化,以此对硬度测试结果进行了分析。结果表明:Ni5Al过渡层的硬度随热处理温度的升高而增加;聚苯酯铝硅涂层的硬度随热处理温度的升高整体呈下降趋势,当温度超过200℃以后,其硬度显著降低,400℃时硬度下降为室温下硬度的13.7%。聚苯酯铝硅涂层中Si元素向过渡层方向扩散,并在过渡层内部及与基体结合处聚集,生成SiO_2。温度越高,扩散现象越明显,过渡层硬度增强。此外,随热处理温度的升高,过渡层内部区域Al元素含量增高,也使过渡层硬度增大。当温度升高时,由于聚苯酯与Al Si热膨胀系数不同且聚苯酯发生晶型转变,导致组织疏松甚至形成孔洞,使涂层硬度降低。

The changes of the hardness of AlSi-polyphenylester seal coating with the temperature and its micromechanism were studied. The hardness of the coating was tested by micro Vickers hardness tester. The distribution changes of Si, Al and other elements in the matrix, Ni5Al transition layer and AlSi-polyphenylester coating were studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The hardness test results were analyzed. The results show that the hardness of the Ni5Al transition layer increases with the increase of heat treatment temperature. The hardness of the AlSi- polyphenylester coating decreases slowly with the increase of heat treatment temperature, when the temperature is over 200℃, the hardness of the coating decreases obviously, and the hardness at 400 ℃ decreases to 13.7% of the hardness at room temperature. Si element in the AlSi-polyphenylester coating diffuses into the direction of the transition layer. The Si element accumulates at the interface between the transition layer and the matrix, and then SiO2 forms. The higher the temperature is, the more obvious the diffusion phenomenon is, and the hardness of the transition layer increases. In addition, with the increase of heat treatment temperature, the content of Al in some regions of the transition layer increases, then the hardness of the transition layer increases. When the temperature increases, due to different thermal expansion coefficients of polyphenylester and AlSi, and the crystal transformation of polyphenylester, the microstructure becomes loose or even forms the holes, which can result in the decrease of the hardness of the coating.