| 航空发动机热障涂层存在的问题及其发展方向 |
| 添加时间：2017/12/2 15:45:50 浏览次数： |
| 一、热障涂层应用现状 1. Application status of thermal barrier coatings 要想使航空发动机获得更大的推重比，就必须提高发动机涡轮前的进口温度，因此对航空发动机燃烧室、涡轮叶片等热端部件的抗高温能力的要求相应提高。在基体合金表面涂覆热障涂层（ Thermal Barrier Coating，TBC）是有效提升其抗高温能力的途径之一 。目前在涡轮发动机上获得实际应用的热障涂层均为双层结构： 表层为陶瓷层，主要起隔热作用，此外还起抗腐蚀、冲刷和侵蚀的作用； 内层为金属粘接层，主要起改善金属基体与陶瓷层之间的物理相容性，增强涂层抗高温氧化性能的作用。 In order to make the engine get greater thrust to weight ratio, it is necessary to improve the engine turbine inlet temperature, the combustion chamber, gas turbine engine hot end components of the high temperature tolerance requirements increase. Coating the thermal barrier coating (Thermal Barrier Coating, TBC) on the surface of the matrix alloy is one of the ways to effectively improve its high temperature resistance. Get the current in the turbine engine on the practical application of the thermal barrier coatings are double-layer structures: surface ceramic layer, mainly has the function of thermal insulation, also play a role of corrosion resistance, erosion and erosion; the inner layer is a metal bonding layer, mainly to improve between metal matrix and ceramic layer physical compatibility, enhanced high temperature resistant coating oxidation properties. 迄今为止，应用最广、最成熟的热障涂层是以氧化钇（质量分数 6% ～8% ）部分稳定氧化锆（ YSZ）陶瓷层为面层，MCrAlY合金层为粘接层的双层结构热障涂层体系。 YSZ具有低的热导率和相对较高的热膨胀系数，但是它在使用过程中存在如下问题： So far, the most widely used and most mature thermal barrier coatings are double-layer thermal barrier coatings with yttrium oxide (mass fraction 6% to 8%), partially stabilized zirconia (YSZ) ceramic layer and MCrAlY alloy layer as bonding layer. YSZ has low thermal conductivity and relatively high thermal expansion coefficient, but it has the following problems in the process of use: （1）当工作温度高于 1200 ℃时，随着烧结时间延长，YSZ 的孔隙率和微观裂纹数量逐步减少，从而导热系数上升，隔热效果下降。 (1) when the working temperature is higher than 1200 C, with the prolongation of sintering time, the porosity and the number of micro cracks gradually decrease, and the thermal conductivity increases. The thermal insulation effect of YSZ decreases. （2）高温环境中，热障涂层的面层和粘接层之间会生成以含铝氧化物为主的热生长氧化物（ TGO），同时金属粘接层会产生“贫铝带”，随着热循环次数的增加，贫铝带扩大，富 Ni、Co的尖晶石类氧化物在TGO 中形成，从而使 TGO 内部产生较大的应力，最终诱发裂纹并导致陶瓷面层脱落。 (2) in the high temperature environment, between the thermal barrier coating surface layer and the adhesive layer will generate thermally grown oxide with aluminum oxide (TGO), and the metal bonding layer will have a "poor aluminium belt", with the increase of thermal cycles, poor aluminum spinel oxide expanded, rich in Ni, Co formed in the TGO, so that TGO generated great stress, induce crack and causes the ceramic surface layer off. （3）空气环境中或飞机跑道上的颗粒物进入燃烧室后，在高温作用下形成一种玻璃态沉积物 CMAS（ CaO，MgO，Al2O3，SiO2等硅酸铝盐物质的简称）。 CMAS 附着在发动机叶片上，在毛细管力的作用下沿着 YSZ 涂层孔隙向深度方向渗透，随后 CMAS与YSZ涂层中的 Y2O3发生反应，加速YSZ相变，最终在热化学与热机械的相互作用下，导致YSZ 涂层内部产生裂纹。 (3) when particulate matter in air environment or runway enters the combustion chamber, it forms a glassy sediment CMAS (CaO, MgO, Al2O3, SiO2 and other aluminum silicate substances abbreviation) under the action of high temperature. CMAS attached to the engine blades, the capillary force along the depth direction to YSZ coating pore permeability, then CMAS and YSZ coating reaction of Y2O3 in YSZ, accelerate the transformation, culminating in the interaction with thermochemical thermo mechanical, resulting in YSZ coating cracks. （4） YSZ 陶瓷面层、金属粘接层、TGO 的热膨胀系数存在的差异会引起致YSZ陶瓷面层/TGO界面、TGO/金属粘接层界面上在从工作温度（上千摄氏度） 降到室温的过程中产生应变失配，从而形成热失配应力，最终会导致YSZ 面层脱落。 (4) the differences of YSZ ceramic layer, metal bonding layer, the thermal expansion coefficient of TGO will cause the YSZ ceramic surface layer /TGO interface and TGO/ interface in metal bonding layer from the working temperature (thousand degrees Celsius) down to the misfit strain produced at room temperature in the process of forming thermal mismatch stress that will eventually lead to YSZ face off. 为了改善 YSZ 涂层性能，人们进行了大量的探索和研究。表1是影响 YSZ 涂层服役寿命的常见问题及其改善需求、改善方法。 In order to improve the performance of YSZ coating, a lot of research and research have been carried out. Table 1 is a common problem that affects the service life of the YSZ coating and its improvement requirements and methods. 1、改善抗烧结性 1, improve the resistance to sintering （1）提高陶瓷涂层纯度，减少 YSZ 涂层中 SiO2和 Al2O3杂质的含量，可以显著降低涂层的烧结速率，平面收缩倾向减小，从而降低导热系数的增加速率，涂层表现出一定的抗烧结性。 (1) improving the purity of ceramic coatings and reducing the content of SiO2 and Al2O3 impurities in YSZ coating can significantly reduce the sintering rate of the coatings, reduce the tendency of plane shrinkage, thereby decreasing the rate of thermal conductivity increasing, and the coating exhibits certain sintering resistance. （2）在涂层中添加特殊化学元素。例如在镧系锆酸盐体系（ La2Zr2O7）涂层中适量掺杂Hf 、Nd、Gd、Sm 等元素能够有效提升涂层的抗烧结性能。 (2) adding special chemical elements to the coating. For example, some elements such as Hf, Nd, Gd and Sm in the lanthanide Zr system (La2Zr2O7) coating can effectively improve the anti sintering properties of the coating. 2、控制 TGO 的生长 2, control the growth of TGO 航空发动机在高温服役过程中，粘接层Al，Cr，Ni 等金属元素接触氧气发生选择性氧化，会在粘接层（ BC） 和顶层陶瓷层（ TC）表面形成一层热生长氧化物（ TGO） ，进而造成涂层局部膨胀并对 TC 产生张力， 当张力超过了TC的结合力时就会引起裂纹扩展，直至表面涂层的剥落。 Aero engine in high temperature service process, adhesive layer Al, Cr, Ni and other metal elements in contact with oxygen selective oxidation, the adhesive layer (BC) and the top ceramic layer (TC) formed on the surface of a layer of thermal grown oxide (TGO), causing the local expansion and tension on the coating of TC, when combined with the tension force more than TC will cause the crack, until the surface coating spalling. （1）改变粘接层的化学成分。适当掺杂一些活性元素（ 如 Y，Hf，Zr），在这些元素的偏析聚集作用下，降低Al2O3的增长速度，抑制TGO 生长； (1) change the chemical composition of the adhesive layer. Proper doping of some active elements (such as Y, Hf, Zr) can reduce the growth rate of Al2O3 and inhibit the growth of TGO under the segregation of these elements. （2）采用冷喷涂（ CS）、超音速火焰喷涂（ HVOF）等工艺或预先沉积一层富 Al 的PVD “薄夹层”，改善涂层结构，降低氧气扩散系数，从而减缓 TGO 的生长速度。 (2) cold spraying (CS), supersonic flame spraying (HVOF) and other processes or pre deposition of a Al rich PVD "thin interlayer" to improve the coating structure and reduce the oxygen diffusion coefficient, thereby slowing down the growth rate of TGO. 3、改善抗CMAS腐蚀性能 3, improve the corrosion resistance of CMAS 发动机叶片上 CMAS 的形成不仅会造成钇的损耗引起 ZrO2熔融相变产生不稳定相，CMAS 的沉积还会引起涂层应力增大，加速涂层剥蚀，大大降低热障涂层的服役寿命。研究发现从以下几方面可改善涂层抗 CMAS 腐蚀性能： The formation of CMAS on the engine blades will not only cause the loss of yttrium, but also cause the unstable phase of ZrO2 fusion phase transformation, and the deposition of CMAS will also cause the stress increase of the coating, accelerate the coating erosion, and greatly reduce the service life of the thermal barrier coating. It is found that the corrosion resistance of the coating can be improved from the following aspects: the CMAS corrosion resistance of the coating can be improved. （1）改变涂层化学成分。在 YSZ 中添加 Al，Ti，Si等元素可诱导生成一种氧基磷灰石相，从而抑制 CMAS 的向涂层内部侵蚀，降低界面层的浸润性能，增强涂层抗 CMAS 性能。 (1) change the chemical composition of the coating. Adding Al, Ti, Si and other elements in YSZ can induce the formation of an oxygen apatite phase, thereby inhibiting the erosion of CMAS to the coating, reducing the wetting performance of the interface layer, and enhancing the CMAS resistance of the coating. （2） 改变涂层结构。烧绿石结构的 Y2Zr2O7中渗入的 CMAS就比一般结构的 YSZ 少很多。对于“ YSZ 内层 + 稀土锆酸盐（ Ln2Zr2O7） 烧绿石外层”、“YSZ +Sm2Zr2O7 ”和“YSZ +Gd2Zr2O7 ”等双层热障涂层，由于烧绿石外层可以减少 CMAS 的渗入，因此热障涂层的抗 CMAS 侵蚀性得到极大提高。 (2) change the coating structure. Burn into Y2Zr2O7 CMAS pyrochlore structure is much less than the general structure of YSZ. The inner layer of YSZ + rare earth zirconate Pyrochlores layer (Ln2Zr2O7) "and" YSZ +Sm2Zr2O7 "and" YSZ +Gd2Zr2O7 "double layer thermal barrier coatings, the pyrochlore outer layer can reduce CMAS infiltration, so the thermal barrier coating anti CMAS corrosion has been greatly improved. 4、 改善YSZ 面层应变容限 4, improve the strain tolerance of YSZ surface layer 采用EB-PVD 技术、等离子物理气相沉积技术（ PS-PVD）、悬浮液等离子喷涂技术（ SPS）等可制备 “柱状”结构的 YSZ 陶瓷面层，通过柱间纵向开裂释放陶瓷面层/TGO 界面上的热失配应 EB-PVD technology, plasma physical vapor deposition (PS-PVD) and suspension plasma spraying (SPS) technology were used to prepare columnar structure YSZ ceramic surface. The thermal mismatch of ceramic surface layer on /TGO interface was released through longitudinal cracking between columns. |
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