粉末结构对冷喷涂纳米结构WC-Co沉积行为的影响

Influence of Powder Porous Structure on the Deposition Behavior of Cold Sprayed Nano-structured WC-Co Coatings

纳米结构WC–Co具有比常规WC–Co更高的硬度,因此受到了广泛关注。冷喷涂制备纳米结构WC–Co涂层过程中,因粒子温度低于熔点,沉积过程需要依靠WC–Co粒子的塑性变形,然而WC–Co粒子变形能力有限,使得WC–Co涂层难以实现有效沉积。文中从粉末结构角度出发,选用3种不同孔隙结构的WC–12Co粉末,运用扫描电镜研究不同结构WC–12Co单个粒子在基体上的沉积行为,分析了3种粉末在相同喷涂工艺参数下沉积的涂层的组织结构。研究发现,定点喷涂容易实现,沉积的WC–12Co沉积层组织结构致密,硬度接近块材,为粉末的连续沉积制备涂层提供了可能。涂层的连续沉积需要粉末和基体材料均产生一定的变形,具有一定孔隙结构的纳米结构WC–Co粉末,因其多孔结构促进了粉末拟变形的发生,适合于冷喷涂制备纳米结构WC–Co涂层。

Nano-structured WC Co gets more attentions for its higher hardness than conventional WC Co. It is difficult to deposit nano-structured WC-Co by cold spraying for the reason that the depositions mainly depend on the deformation of the powders while the powders have poor deformability with the temperature lower than the melt points during the deposition. Three powders with different porosities were used for this work, the cross-section and surface morphology of the single particles deposition were characterized. The microstructures of the coatings prepared with three powders in the same parameters were examined. It was found that the deposit can be prepared easily at fixed position which provides the possibility of successfully built-up of WC-Co coatings, its microstructure is dense and its hardness can be comparable to the bulk one. Successfully built-up of WC-Co coatings need certain deformations of both substrates and powders. Powder with certain porous structures which could promote powders deformation was suitable for the built-up of WC-Co coatings by cold spraying.