镀铝表面改性7YSZ纳米热障涂层热震性能分析

Thermal Shock Analysis of Surface Al-modified 7YSZ Nano-thermal Barrier Coating

为提高7YSZ纳米热障涂层的热震性能,实验中采用超音速火焰喷涂(HVOF)在涡轮叶片模拟工件上制备了粘结层NiCrCrAlYTa,再使用大气等离子喷涂(APS)在粘结层上制备了7YSZ纳米陶瓷层。采用磁控溅射在7YSZ热障涂层样品表面镀铝,并在不同压力下(200、250、300 Pa)对镀铝样品进行热处理表面改性。对喷涂态样品和镀铝改性后样品进行水淬热震实验,1050℃保温10 min+水冷5 min为一个热循环,观察热障涂层镀铝改性前后样品在水淬热循环过程中形貌和结构演变。实验结果表明,镀铝改性后样品表面存在铝薄膜蒸发、凝固后形成的疏松纳米Al晶粒表层以及由Al和ZrO_2原位反应形成的致密α-Al_2O_3底层。在镀铝样品热处理过程中,随着压力升高,疏松层致密度逐渐增加。不同热处理压力下镀铝表面改性后样品经过73次水淬热循环后剥落面积均小于喷涂态样品,显示出良好的抗热震性。

In order to improve the thermal shock resistance of 7YSZ nano-thermal barrier coating （TBC）, bond coating NiCoCrAlYTa was prepared on simulated turbine blade by HVOF （high velocity oxygen flame）. Subsequently, 7YSZ nano-ceramic coating was produced on bond coating as top coating. Al film was deposited on the surface of TBC samples. Then the Al-deposited TBCs were carried out by heat-treatment at different pressures （200, 250, 300 Pa）. After that, the thermal shock tests of as-sprayed and Al-modified 7YSZ nano-TBC were taken from 1050 ℃ to atmospheric water with holding time of 10 and 5 min, respectively. Micrograph and microstructure evolution of the TBC sample were characterized before and after thermal shock. The results show that a loose top layer with Al nano-grains is formed on the TBC surface due to evaporation and condensation of Al film at vacuum pressure. Besides, with increase of heat-treatment pressure, the density of loose layer is increased. A dense Al2O3 layer was in-situ synthesized under the loose layer due to the reaction of Al and ZrO2. The Al-modified 7YSZ nano-TBCs heat-treated at different pressures has less spallation area than the as-sprayed TBCs after withstood 73 thermal shocks, showing better thermal shock resistance.