【作者】 徐金；

【导师】 李志林；

【作者基本信息】 北京化工大学 ， 材料物理与化学， 2008， 硕士

【摘要】 热障涂层是高温下被应用于热端部件表面的一种涂层,通过在基体合金表面涂覆陶瓷层进行隔热,来提高部件的工作效率及寿命。粘结层是在陶瓷层与金属基体之间的一层改善陶瓷层与基体粘结性的过渡层。在热障涂层工作过程中,粘结层部分元素被氧化,在粘结层与陶瓷层之间生成热增长氧化物（TGO）,实验证明,热障涂层的失效往往发生在陶瓷层与粘结层之间的界面结合处。本文以固体与分子经验电子理论（EET）和改进的TFD理论为基础,从晶体价电子结构和界面电子结构的角度,对热增长氧化物层中α-Al₂O₃的价电子结构进行了分析。计算了不同Al、Y、Cr、Co、Hf含量的粘结层与热增长氧化物层之间的界面结合因子,通过界面结合因子σ（或σ′）,ρ_（hkl）,ρ_（uvw）,△ρ_min,σ_equal,σ_super的计算结果分析得出:1.粘结层中添加铝的含量在2-wt%时,对于界面粘附性是最有利的;在铝含量低于10-wt%时,有利于改善TGO与粘结层之间的界面粘附性,而高于10-wt%是不利于界面结合的。铝含量低于或等于8-wt%时应该是有利于缓解界面的应力的。2.当粘结层的取向为（111）和（100）时,加Y可以改善该界面的界面结合。但当粘结层取向为（110）时,只有Y含量高于0.7-wt%时才能使△ρ_min比无Y时小,在0.7-wt%时达到最小,同时,粘结层的面电子密度ρ也是在0.7-wt%时才比未添加时高,且随着Y含量的增加有下降趋势。综合分析表明,粘结层中Y的含量在0.7-wt%～0.9-wt%有利于粘结层界面结合的稳定。3.不论粘结层处于何种位相,Co的加入都有利于缓解界面应力以及保持界面电子密度的连续性,且在10～14-wt%趋于最佳。当粘结层的表面为（110）时,Co含量的增加有利于提高界面的结合力,而当粘结层的表面为（100）和（111）时,界面的结合力不受Co含量影响。4.当粘结层的取向为（111）和（100）时,加Cr可以改善该界面的界面结合。如能控制工艺因素,使粘结层出现表面为（111）或（100）的织构,则加Cr可以改善TGO/粘结层界面的界面结合。在目前工艺条件控制织构比较困难的情况下,从界面结合考虑,热障涂层粘结层中含Cr量应尽量降低。5.Hf的添加是改善该界面结合的,且在低于1.3-at%（3.9-wt%）Hf含量的范围内,这些界面结合因子都趋向于较佳的状态。可以认为,在满足Ni基粘结层强度、韧性、抗热腐蚀性要求的适当含量的Hf可改善热障涂层的TGO/粘结层的界面结合。更多还原

【Abstract】 Thermal barrier coatings （TBCs） are commonly used to the surface of thermo-parts. TBCs can improve the work efficency and longevity of parts by covering top coat on the surface of alloy substrate. Bond coat is a kind of coating that improved the interface conjunction between the bond coat and the top coat. Some elements of bond coat are oxidized and forms thermally grown oxide （TGO） between bond coat and ceramic top coat during the application of the thermal barrier coatings. It is proved by experiments that the failure of TBCs typically occurs at the interface between the bond coat and the TGO.Based on the Empirical electron theory in solid and molecule （EET） and improved Thomas-Fermi-Dirac （TFD） theory in this thesis, the valence electron structure ofα-Al₂O₃ in the thermally grown oxide （TGO） are analyzed, and that is in view of the valence electron structure and interface electron structure of the crystals. The interface conjunction factor between the bonding layer and ceramic layer of the thermal barrier coatings of different content of Al、Co、Cr、Y、Hf are calculated. The results are as following. Considering the electron density parameters ofρ,△ρ_min,σ,σ_super,σ_equal on the bond-coat/TGO interface, the following conclusion can be obtained:1. Considering the cohesion force of the interface, the most favorable aluminium content of the bond-coat is 2-wt%. The aluminium content beneath 10-wt% is favorable, and the aluminium content over 10-wt% is harmful in this case. The aluminium content of the bond-coat being not more than 8-wt% is considered to decrease the interface stress.2. When the orientation of the bonding layer is （100） or （111）, the addition of Y can improve the interface conjunction. When the orientation is （110）, the electron density parameters of△ρ_min is lower than the one without Y when the Y content is more than 0.7-wt%; Furthermore,△ρ_min is the lowest when the Y content is 0.7-wt%. The electron density with Y content of 0.7-wt% of its （110） crystal plane is higher than without Y, and the interface electron density slightly decreases with the increase of the yttrium content when the yttrium content is higher than 0.7-wt%. Comprehensive analysis indicates that the bond-coat yttrium content of 0.7-wt%-0.9-wt% or a little higher is also suitable for the stability of the interface cohesion of the bond coat.3. No matter what orientation of the bonding layer in, the addition of Co can be in favor of the release of interface stress and keep the continuity of the interface electron density. At the same time, the Co content of 10-wt% -14-wt% is the optimal. While the orientation of the bonding layer is （110）, the increasing of Co content can enhance the interface conjunction. However, when the orientation is （100） or （111）, the content of Co almost has no effect.4. When the orientation of the bonding layer is （100） or （111）, the addition of Cr can improve the interface conjunction of the interface. If the factors of techniques can be controlled and formed orientation of being （111）, （100） in the bonding layer, the addition of Cr can improve the interface conjunction between the bond coat and the TGO. Therefore, in the situation when the texture in the bonding layer is controlled with difficulty, considering the interface conjunction, the content of Cr of Ni-based bonding layer should be reduced as low as possible.5. The additional of Hf is beneficial for the interface conjunction. Furthermore, these interface conjunction factors tend to the better estate beneath the Hf content of 1.3-at% （3.9-wt%）. It is thought that the suitability Hf content can improve the interface conjunction between the bond coat and the TGO at the condition of meeting the intensity, toughness and anti-thermo -causticity of Ni-based bond coat.更多还原