等离子喷涂未烧结YSZ喷雾造粒粉体涂层中纳米结构特征研究

Characteristics of Nano Zone Structure of the Plasma-sprayed Coatings with Spray Dried YSZ Agglomerates with No Sinter Treatment

目的 解决未烧结纳米结构团聚体颗粒的喷涂问题,通过使用未烧结团聚体粉末使涂层获得更多且与原始粉体尺度相近的纳米颗粒。研究未烧结粉体沉积时,纳米结构特征随电弧电流变化的关系。方法 利用延长喷嘴喷枪实现了未烧结氧化钇稳定氧化锆（YSZ）喷雾造粒粉体的有效沉积。在电流150、200、250 A下分别制备具有不同纳米结构的YSZ涂层,并利用场发射扫描电子显微镜与X射线衍射观察微观结构,尤其是纳米结构特征的变化及相结构。利用德拜谢乐公式计算涂层的平均晶粒尺寸。通过对低载荷下的维氏硬度进行Weibull分析来了解涂层的微观结构。结果 采用延长喷嘴技术,粉末经延长喷嘴处送入等离子射流,未烧结粉沉积效率可达21.2%～40.2%。涂层平均晶粒尺寸约为44～56nm。200 A时涂层中具有紧密且未被周围熔化部分包围的纳米结构,含量约为37%。进一步增加或降低电弧电流得到的涂层中的纳米结构具有不同的特征,这种差异可通过Weibull曲线的比较分析来印证。结论 实验采用的喷枪装置能够有效地喷涂疏松且结合强度较低的未烧结团聚体粉末,涂层平均晶粒尺度显著降低。

Objective To solve the spraying problems of unsintered nanostructured agglomerates, retain more nano particles that resemble to the original powder in size and study the relation between nano structure features and arc current change when unsintered nanostructured agglomerates are deposited. Methods The deposition of unsintered YSZ spray dried agglomerates was carded out by extending the gun barrel. YSZ coatings with different nano structures were fabricated with the current of 150 A, 200 A, 250 A respectively. The microstructure, especially the nano structure feature change and phase structure were in- vestigated via field emission scanning electroscopic and X-ray diffraction method. The average grain size of the as-sprayed coatings was evaluated through Debye-Scherrer formula. The Weibull analysis of Vicker＇s microhardness under lower load was also adopted to analyze the character of the nanostructured coatings. Results Powders entered plasma jet via extended gun barrel and the deposition efficiency of unsintered agglomerates reached 21.2%-40.2%. The average grain size of the as-sprayed coat- ings was evaluated to be 44-56 nm. The content of the compacted and less infiltrated nano-zone reached the peak value of 37% with the arc current of 200 A. The nano zone exhibited different structures when the arc current was further increased or de- creased, the characteristics of which could be further illuminated by Weibull analysis. Conclusion The gun configuration used in this study is effective in spraying unsintered agglomerates which are porous and weak bounded and reducing the average grain size of the as-sprayed coatings.