镍铬−莫来石复合陶瓷涂层热障及抗热震性能的研究

Research on thermal barrier and thermal shock resistance of NiCr−mullite composite ceramic coating

使用球磨法混制了五组不同比例的镍铬−莫来石复合粉末,利用超音速等离子喷涂技术在45钢基材表面制备相应的镍铬−莫来石复合陶瓷涂层,测定涂层导的热系数和抗热震性能,采用扫描电子显微镜观察涂层表面、截面显微形貌,利用能谱仪分析涂层特征区的组织成分,通过X射线衍射分析涂层组织结构。结果表明,镍铬−莫来石复合涂层以镍铬固溶体为基体,其上均匀分布着莫来石颗粒,莫来石与基体之间形成了扩散相,提高了莫来石与基体之间的润湿性,使莫来石被基体牢固包覆;莫来石颗粒的加入强化了基体,在莫来石体积分数38%~75%范围内,随着莫来石含量的增加,涂层强韧性增加,抗热震性提高,热导率降低。

Five groups of the NiCr−mullite composite powders in various proportions were mixed by ball milling.The NiCr−mullite composite ceramic coatings on the 45 Steel were prepared by the supersonic plasma spraying.The thermal conductivity and thermal shock resistance of the coatings was tested.The microstructures of the coating surface and cross section were observed by the scanning electron microscope(SEM),the chemical composition in the characteristic area of coatings was analyzed by the energy disperse spectroscopy(EDS),and the phase constitution of the coatings was analyzed by X-ray diffraction(XRD).The results show t hat,the NiCr solid solution is the matrix of the NiCr−mullite composite coatings,which is uniformly distributed by the mullite particles.The diffusion phases are formed between the mullite particles and the NiCr matrix to improve the wettability,and the mullite particles can be coated firmly by the diffusion phases and the NiCr matrix.Meanwhile,the NiCr matrix can be reinforced by the mullite particles.The strength toughness and the thermal shock resistance of the coatings increase,and the thermal conductivity reduces with the increase of the mullite volume fraction from 38%to 75%.