冷喷涂和低压等离子喷涂Ni-Ti涂层：组织和性能

Cold sprayed and low pressure plasma sprayed Ni-Ti coatings: microstructures and properties

摘要:

采用原子比1：1的Ni和Ti为原料,通过冷喷涂(CS)和低压等离子喷涂(LPPS)制备了Ni-Ti复合涂层,研究喷涂工艺对涂层的组织(孔隙率、相组成和显微组织)和性能(硬度、耐磨性和耐蚀性)的影响。结果表明：两种涂层均未发生明显的氧化,但表现出不同的组织结构。高速碰撞后的颗粒发生严重塑性变形使CS涂层具有低的孔隙率,且XRD未检测到其它的相生成；层片状结构的LPPS涂层内部形成了Ni-Ti金属间化合物相,其表现出高的显微硬度和低的磨损率。此外,LPPS涂层高的腐蚀电位和低的腐蚀电流密度,表明其高的耐蚀性。

Abstract:

In this study, cold spray (CS) and low pressure plasma spray (LPPS) were chosen to fabricate the Ni-Ti composite coatings using a mechanically mixed powder of Ni/Ti at the atomic ratio of 1:1 aiming to avoid the oxidation. Upon utilization CS and LPPS techniques, spray processes played a significant role in the microstructures, phase compositions, mechanical property, and wear and corrosion performances of the two coatings. Results show that no oxidation was characterized in these two coatings. Nevertheless, two very different coating structures were found. CS coating showed a much lower porosity and a mechanical bonding of plastically deformed particles, and XRD denoted no NiTi intermetallic was formed during CS deposition. However, high temperature would lead to the significant differences in the LPPS coating, which exhibited a lamellar structure with the formation of Ni-rich and Ti-rich intermetallics around the interface. The LPPS coating presented the excellent performances due to the element diffusion during LPPS process. For example, it yielded a higher hardness value, which was nearly three times higher than that of CS coating. It was also given that a significant reduction of wear rate. In addition, a much higher corrosion potential and a much lower corrosion current also indicated a better corrosion resistance of LPPS coating.