[2Ip01-07] Vacuum Science Technology (VST)

[2Ip04] Vacuum firing effect on stainless steel for outgassing reduction

*Junichiro Kamiya¹, Kazuhiro Takano^1,4, Kaoru Wada², Toru Yanagibashi^1,3 (1. Japan Atomic Energy Agency, 2. Tokyo Electronics Co., Ltd., 3. NAT Corp.,, 4. ULVAC TECHNO, Ltd.)

The effect of the vacuum firing on the stainless steel has been evaluated from the vacuum and surface point of view. In the build-up test, the vacuum-fired stainless steel vacuum chamber showed lower outgassing than the non-vacuum-fired chamber. Especially the hydrogen outgassing was well reduced in the vacuum-fired chamber. The TDS showed that the vacuum firing reduced the desorption of H₂, H₂O, CO, and CO₂ with high desorption energy even after air exposure. Especially the reduction of the H₂ desorption was very large. The XPS showed an increase of Fe-oxide and a decrease of Cr-oxide on the outermost surface of the vacuum-fired stainless steel. The XPS also showed that the Cr-oxide was systematically increased by heating at 200℃, 300℃, and 400℃. These results support the outgassing reduction mechanism by vacuum firing that the hydrogen is reduced from the bulk due to the diffusion to the vacuum phase during the vacuum firing. In addition, it is also considered that the reformed surface metal oxides by the air exposure after vacuum firing act as a barrier, which prevents gas molecules from being reabsorbed on the surface or reabsorbed into the bulk.