采用压力热处理工艺对金属钨进行表面纳米化处理

Nanocrystallization on Surface Layer of Tungsten Using Pressure-Assisted Heat Treatment Process

摘要:

为进一步提高金属钨工件在高能辐照、电弧烧蚀等工况下的使用寿命，有必要对钨进行表面纳米化处理，提高表层材料的抗疲劳、耐辐照等性能。然而，由于钨的高熔点和高硬度，使其表层材料发生塑性变形或局部熔化十分困难。本工作以纯钨板为原料，对其施加10 MPa压力，在真空中将其加热至900 ℃并保温3 h，采用压力热处理工艺对钨板进行表面纳米化处理。结果显示处理后，在钨板表面形成了厚度2~4 μm的纳米晶层，晶层厚度均匀。纳米晶粒呈等轴状，平均晶粒尺寸普遍小于300 nm。钨板内部依然保持为粗晶组织，表面纳米晶层与基体粗晶组织之间结合牢固，无明显界面。本工作有望为钨等难熔金属表面纳米化探索一种更加高效便捷的技术路径，具有重要的理论意义和实际应用价值。

Abstract:

To further improve the service life of tungsten (W) workpieces under harsh working conditions such as high-energy irradiation and arc erosion, it is necessary to carry out nanocrystallization treatment on the W surface to further improve the fatigue resistance and radiation resistance of surface materials. However, due to the high melting point and high hardness of W, it is very difficult for the surface material of W to undergo plastic deformation or local melting. This research used pure W plate as raw material. The W plate was applied with a pressure of 10 MPa, and then it was heated to 900 ℃ in a vacuum environment and kept at this target temperature for 3 h. The surface of W plate was treated by the pressure-assisted heat treatment process. The results show that for the treated W plate, a nanocrystalline layer with a thickness of 2–4 μm is formed on its surface, and the nanocrystal layer exhibits a uniform thickness. The nanocrystals are equiaxed in shape, with an average grain size generally less than 300 nm. However, the microstructure inside W plate still keeps coarse grains. The nanocrystalline layer is firmly bonded to the internal coarse grains, without any obvious interfaces. This work is potentially to explore a more efficient and convenient technical path for the surface nanocrystallization of refractory metals such as W, which has important theoretical significance and practical application value.