Corrosion and microstructure evolution of He+ plasma irradiated tungsten PFMs

Abstract

The microstructure, composition and surface roughness of W-PFMs were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and atomic force microscopy (AFM) under different He+ plasma irradiating conditions. Apparent roughness(damage) evolution in the surfaces of W-PFMs were studied, revealing the forming process of wavy, step-like and fuzz structures under different irradiation doses. The differences in the corrosion resistance of unirradiated as well as irradiated W-PFMs were investigated respectively, by potentiodynamic polarization curves and neutral salt spray tests (NSS). The experimental results showed that the He+ plasma irradiated materials(W-FZ60) had better corrosion resistance, with 3.79 times of AC impedance value than that of unirradiated tungsten. After 720 h of neutral salt spray test, the surface of unirradiated specimen showed numbers of continuous cracks in the substrate. In contrast, no apparent micro-cracks and other damages were found in the surface of He+ plasma irradiated specimens under the same NSS testing. In this paper, the macro- to micro- bridge had been built to elaborate the damage evolution during irradiating, such as fuzz structure formed in higher irradiations in this study, which played important roles in blocking access to corrosives, further enhancing corrosion resistance of the irradiated W-PFMs.