Laser Stimulated Grain Growth in 304 Stainless Steel Anodes for Reduced Hydrogen Outgassing

TL;DR

This study demonstrates that laser surface melting of 304 stainless steel anodes significantly reduces hydrogen outgassing by increasing grain size, thereby decreasing hydrogen trapping sites, which enhances vacuum electronic device performance.

Contribution

It introduces a laser surface melting technique to enlarge grain size in stainless steel anodes, reducing hydrogen outgassing and improving their suitability for vacuum electronics.

Findings

Hydrogen outgassing reduced by ~4 times after laser treatment.

Grain size increased from 40 to 3516 micrometer².

Laser-treated anodes show improved vacuum performance.

Abstract

Metal anodes in high power source (HPS) devices erode during operation due to hydrogen outgassing and plasma formation, both of which are thermally driven phenomena generated by the electron beam impacting the anode s surface. This limits the lowest achievable pressure in an HPS device, which reduces its efficiency. Laser surface melting the 304 stainless steel anodes by a continuous wave fiber laser showed a reduction in hydrogen outgassing by a factor of ~4 under 50 keV electron bombardment, compared to that from untreated stainless steel. This is attributed to an increase in the grain size (from 40 - 3516 micrometer2), which effectively reduces the number of characterized grain boundaries that serve as hydrogen trapping sites, making such laser treated metals excellent candidates for use in vacuum electronics.