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

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.