复合溶胶-凝胶法制备TiAl合金表面防护涂层及其高温抗氧化性能

Preparation and high-temperature anti-oxidation property of protection coatings onγ-TiAl alloys by composite sol-gel method

采用复合溶胶-凝胶法在γ-TiAl合金表面制备一种致密均匀的新型复合陶瓷涂层。通过1000℃等温氧化和循环氧化实验研究涂层对γ-TiAl基体高温氧化行为的影响,并初步探讨涂层的抗氧化机制,利用扫描电镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)分析涂层氧化产物的表面形貌、组织结构及相组成。结果表明:涂层对TiAl基体具有良好的高温防护作用,能显著降低TiAl合金的高温氧化速率;涂层氧化产物Y_3Al_5O_(12)和Y_2(Ti_2O_7)的热膨胀系数与TiAl基体的非常接近,提高涂层和基体之间的相容性,从而避免涂层在氧化过程中的剥落。BSE和EDS分析表明,在涂层与基体界面处形成一层致密的Al_2O_3保护膜,有效地防止合金基体的高温氧化。

A new compact and uniform composite ceramics coating was prepared on γ-TiAl alloys by composite sol-gel method, using the composite sol constituted of Y sol as binder and TiAl3/TiN as nano-powders. The effect of coatings on the high-temperature oxidation behavior of TiAl alloys and its anti-oxidation mechanism were discussed based on isothermal and cyclic oxidation experiments at 1 000 ℃. The surface morphology, microstructure and phases of the coating after oxidation were investigated by scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS） and X-ray diffractometry （XRD）, respectively. The results show that the coating can obviously decrease the oxidation rate of TiAl alloys and effectively avoid cracking and spallation of the oxidation layer during oxidation because the thermal expansive coefficient of Y3Al5O12 and Y2（Ti2O7） is similar to that of TiAl substrate. SEM and EDS analysis indicates that a compact Al2O3 film forms at the substrate/coating interface during oxidation, which can effectively prevent the oxidation of TiAl substrate due to oxygen diffusion.