双组元推力室热防护涂层工艺技术研究

Research on thermal protection coating technique of bipropellant thrust chamber

针对双组元姿轨控发动机推力室铌铪合金材料的高温抗氧化防护进行了涂层工艺技术研究,在合金表面制备了Si-Cr-Ti体系硅化物涂层,通过真空烧结、高温抗氧化和热震试验、显微组织分析,对涂层的成型过程、形貌、组织结构、性能和防护机理进行了分析。结果表明,通过真空烧结形成了过渡/结合层、致密层和疏松层结构的硅化物涂层,过渡层分布均匀,致密层厚实,疏松层相对较薄且成型较好,经过两代工艺优化,涂层在1 700℃下的氧化寿命达到7 h,1 400~8 00℃空冷热震循环寿命达到4 500次,在热试车考核过程中涂层最高工作温度可达到1 350℃,试后涂层依然具有一定厚度的致密层,具有高温防护作用,满足型号对涂层性能的要求。

The coating technology for protecting the Nb - Hf alloy bipropellant thrust chamber of atti- tude and orbital control engine from high - temperature oxidation is studied in this paper. The Si - Cr - Ti system silicide coating was prepared on the surface of Nb - Hf alloy. The forming process, morphology, structure, properties and protective mechanism of the coating were analyzed by vacuum sintering, high - temperature anti- oxidation experiment, thermal shock experiment and microstructure analysis. The re- suhs show that the silicide coating formed by vacuum sinitering consists of transition/bonding layer, （lense layer and loose layer; the distribution of transistion layer is uniform, the dense layer is thick and the loose layer is relatively thin but has a good morphology. With two generation of process optimization, the oxidation life of the coating reaches up to 7 h at 1 700℃ and the air - cooling and ther,nal shock cycle life reaches to 4 000 times at 1 400 - 800℃. During the hot test assessment process, the maximum oper- ating temperature of the coating reached 1 350℃. After the test, the coating still has a certain thickness dense layer. The test result indicates that the silicide coating can provide high - temperature protection and meet the coating performance requirements.