Abstract
Anodes of 304 stainless steel have been processed by a continuous wave Yb fiber laser with a wavelength of 1.064μm and subjected to 50keV electron bombardment in order to determine the extent to which hydrogen outgassing is reduced by the laser surface melting treatment. The results show a reduction in outgassing, by approximately a factor of four compared to that from untreated stainless steel. This is attributed to a reduction in the number of grain boundaries which serve as trapping sites for hydrogen in stainless steel. Such laser treated anodes do not require post-processing to preserve the benefits of the treatment and are excellent candidates for use in high power source devices.
Highlights
High Power Source (HPS) devices are used in numerous applications including vacuum electronics [1,2,3], particle acceleration [4,5], and microwave generation [2,6]
In order to form samples for depth characterization and outgassing evaluation, the stainless steel (SS) samples were processed by raster scanning the laser beam across the surface in a uniform pattern
These features represent areas of the SS surface morphology that were incompletely melted by laser surface melting (LSM) and most likely result from the specific choice of scan parameters for the results shown here
Summary
High Power Source (HPS) devices are used in numerous applications including vacuum electronics [1,2,3], particle acceleration [4,5], and microwave generation [2,6]. Electropolishing has been the method of choice [8,11,15] since it both reduces the surface roughness of anode materials and creates an oxide layer that further reduces hydrogen outgassing. The LSM processing technique entails irradiating a sample with the output of a high energy continuous laser beam, thereby causing melting, flow and resolidification of the material as the laser beam is scanned across the sample surface. This process has the potential of reducing outgassing by forming a more crystalline layer (with fewer grain boundaries), thereby reducing the number of potential sites that can trap hydrogen in the metal [16]. We show here that LSM processing of 304SS does lead to reduced H2 outgassing during electron bombardment
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