Manufacturing of magnetron sputtering tungsten coatings and irradiation damage behavior under helium plasma exposure

Tungsten coatings with different surface morphologies and microstructures were prepared on a reduced activation ferritic/martensitic steel CLAM by DC magnetron sputtering. The sputtering power during coating deposition was varied from 30 W to 60 W in the experiments. The as-deposited tungsten coatings were subjected to He plasma at a sample temperature of ∼758 K with an ion flux of ∼3.0 × 10 21 m −2 s −1 , an incident ion energy of ∼20 eV, and an ion fluence of ∼5.3 × 10 24 m −2 . The tungsten coating deposited at the sputtering power of 40 W successfully gained a unique needle-like morphology and a uniform grain size of ∼100 nm. The coating combined well with the CLAM steel substrate. The nano-sized microstructure brings in high-density grain boundaries and provides sufficient He release channels. Therefore, this dense structure is preferred as an important sink of irradiation-induced defects and thus exhibits excellent He plasma resistance. The formation of fuzz is correlated with the He plasma fluence. Accordingly, our work focused on the investigation of the damage behavior of tungsten coatings under the variation of He plasma irradiation influence. The surface damage morphology of the W coating exhibited a surface bulge, a localized fibrous structure, and a fuzz structure when the irradiation influence was 5.0 × 10 23 , 2.0 × 10 24 , and 1.0 × 10 25 m −2 , respectively. Many fuzz fiber structures were generated at the He plasma fluence of up to ∼1.0 × 10 25 m −2 . The damage of the tungsten coating increased in severity with the ion fluence until the columnar crystal failed. • Tungsten coatings with different surface morphologies and microstructures were prepared by DC magnetron sputtering. • The tungsten coating deposited at sputtering power of 40 W gained a unique needle-like morphology and showed resistance to helium plasma irradiation. • With increasing He ion fluence, the damage of tungsten coating becomes more severe until the columnar crystal fails.