Development of High-Heat Resistant Materials for Aerospace Use by Means of Gas Tunnel Type Plasma Reactive Spraying

1）采用气体隧道式等离子体反应喷涂技术，在功率为25 kW，时间为5s的条件下，在短时间内获得了厚度为150μm的氮化钛（TiN）涂层。研究了横道数、送粉速率、环境气体等因素对TiN涂层性能的影响，确定了最佳工艺条件。2）TiN涂层横截面硬度均匀，孔隙率随横道数的增加而减小。TiN涂层的结合强度约为14 MPa，随厚度的增加而降低。结果表明，100μm厚的涂层具有较好的机械性能，如耐磨性。3）所得TiN涂层的TiN含量大于95%，且随N_2气体混合比的增加而增加。热处理后，TiN涂层的性能得到改善，没有发生氧化。4）采用气体隧道式等离子喷涂技术制备的高硬度氧化锆（ZrO_2-Al_2O_3）复合涂层具有硬度梯度功能。随着Al_2O_3含量的增加，ZrO_2-Al_2O_3梯度功能复合涂层的性能增强，涂层致密。Al_2O_3的高硬度和ZrO_2的低热导率的结合将有助于高梯度功能陶瓷的发展（热障涂层）。5）等离子体温度在炬出口处为8000 K，并且喷涂颗粒速度为150 m/s，随着等离子体输入功率的增加而增加。6）该研究证明这些涂层可用作航空航天用的高耐热材料，采用气体隧道式等离子喷涂和/或反应喷涂方法。

The results obtained by this study are as follows :1) The titanium nitride (TiN) coatings of 150μm thickness were obtained at P=25kW, t=5s in a short time operation, by means of the gas tunnel type plasma reactive spraying. Some coating characteristics which depend on the traverse number, powder feed rate, the environmental gas, etc. were clarified and the optimum condition was decided.2) The hardness of TiN coating was uniform in the cross section and the porosity was decreased with increase in the traverse number. The adhesion strength of TiN coating was about 14 MPa, and was decreased as the thickness was increased. As the results, 100μm thickness coating had better mechanical properties such as wear resistance.3) The TiN ratio of the obtained TiN coating was more than 95%, and was increased with increased in the mixing ratio of N_2 gas. After heat treatment the property of the TiN coating was improved without oxidation.4) High hardness zirconia (ZrO_2-Al_2O_3) composite coating formed by gas tunnel type plasma spraying had a graded functionality of hardness. With increase in Al_2O_3 mixing ratio, the graded functionality ZrO_2-Al_2O_3 composite coating was enhanced and dense coating was obtained. The combination of high hardness of Al_2O_3 with the low thermal conductivity of ZrO_2 will contribute the development of high functionally graded TBC (thermal barrier coating).5) The plasma temperature was 8000K at the torch exit, and the sprayed particle velocity was 150m/s, which were increased with increase in the plasma input power.6) This study proved that these coatings was available as High-Heat Resistant Materials for Aerospace Use, by using of gas tunnel type plasma spraying and/or reactive spraying method.