TiAl合金表面热障涂层的高温抗氧化性能研究

High Temperature Oxidation Resistance of Thermal Barrier Coatings on the Surface of TiAl Alloy

利用大气等离子喷涂技术(APS)在TiAl合金基体表面制备TiAl_(3)/Al_(2)O_(3)-13TiO_(2)纳米热障涂层。采用SEM、EDS和XRD技术分析纳米热障涂层在氧化前后的微观组织及相组成,并对其在950℃下的抗氧化性能进行测试。结果表明,TiAl合金表面制备TiAl_(3)/Al_(2)O_(3)-13TiO_(2)纳米热障涂层后高温抗氧化性能显著提高,氧化动力学曲线呈对数变化规律,950℃高温氧化时,氧化速率常数为3.7×10-3 mg2·cm4/s。在高温氧化过程中,TiAl_(3)粘结层与TiAl合金基体之间发生元素扩散,TiAl合金基体与粘结层之间界面消失。在陶瓷层与粘结层之间形成均匀连续的热生长氧化物层(TGO),在TiAl_(3)粘结层完全降解为TiAl_(2)相和三元Ti-Al-O化合物后,TGO对陶瓷层和粘结层仍具有良好的粘附性,减少氧气向内扩散。陶瓷涂层可以延缓氧原子的大量扩散,同时避免粘结层过度氧化。因此,TiAl_(3)/Al_(2)O_(3)-13TiO_(2)纳米热障涂层能够有效地提高TiAl合金基体的高温抗氧化性。

TiAl_(3)/Al_(2)O_(3)-13TiO_(2)nanostructured thermal barrier coating was prepared on the surface of TiAl alloy substrate by atmospheric plasma spraying(APS).The microstructure and phase composition of nanostructured thermal barrier coating before and after oxidation were analyzed by SEM,EDS and XRD,and the high-temperature oxidation resistance at 950℃was characterized.The results indicate that the high-temperature oxidation resistance of TiAl_(3)/Al_(2)O_(3)-13TiO_(2)nanostructured thermal barrier coating on TiAl alloy is significantly improved,and the oxidation kinetic curve presents a logarithmic variation pattern,where the oxidation rate constant is 3.7×10^(-3)mg^(2)·cm^(4)/s at 950℃.During the high temperature oxidation process,elemental diffusion occurs between TiAl_(3)bond layer and TiAl alloy,and the interface between TiAl alloy and bond layer disappears.A uniform and continuous thermally grown oxide layer TGO is formed between ceramic layer and bond layer,which possesses desirable adhesion to the ceramic layer and bond layer even after TiAl_(3)bond layer is completely degraded to TiAl_(2)phase and ternary Ti-Al-O compound,reducing the inward diffusion of oxygen.The ceramic coating can retard the massive diffusion of oxygen atoms while avoiding excessive oxidation of bond layer.Therefore,TiAl_(3)/Al_(2)O_(3)-13TiO_(2)nanostructured thermal barrier coating can effectively enhance high-temperature oxidation resistance of TiAl alloy.