采用由喷雾造粒制备的纳米团聚粉末并通过等离子喷涂制备出纳米Al2O3-13wt％ TiO2涂层.研究分析了涂层的相组成、显微结构、硬度及断裂韧性,结果发现,该纳米涂层呈现出由两部分不同区域组成的双态分布结构:一部分为完全熔化后凝固形成的层状结构;另一部分则为部分熔化的粒状结构,其内保留来源于喷涂喂料的纳米或亚微米粒子.涂层中与未熔纳米α-Al2O3粒子含量成比例的部分熔化区百分数可以通过调整关键喷涂工艺参数(CPSP)来控制.纳米涂层所具有的这种混合结构特性,可以被其力学性能的双态分布特征所证实.Weibull统计分析表明,涂层的显微硬度和断裂韧性均呈现出双态分布,部分熔化区的显微硬度及其分散性均比完全熔化区低,而其断裂韧性及其分散性则均比完全熔化区高.
Nanostructured Al2O3-13wt％ TiO2coatings were prepared by plasma spraying agglomerated nanocrystalline powders formed via spray drying method.The phase composition,microstructure,microhardness and fracture toughness of the coatings were investigated.It is found that the nanostructured coatings exhibited a unique bimodal microstructure consisting of two distinct regions:one of the regions is Fully Melted (FM) and solidified as lamellar structure,and the other is Partially Melted (PM) particulate microstructure with embedded nano or sub-micron particles retained from the starting powders.Furthermore,the percentage of PM region,which is proportional to unmelted α-Al2O3 nanoparticles,in the coatings can be controlled by the critical plasma spray parameter.Such a characteristic of blended microstructure of the coatings is clearly confirmed from a bimodal distribution of their mechanical properties.The Weibull statistical analysis shows that the microhardness and fracture toughness of the coatings present a bimodal distribution,the mean value and the dispersity of microhardness of PM region are lower than those of FM region,but the mean value and the dispersity of fracture toughness of PM region are both higher than those of FM region.
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