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    Vacuum Science & Technology Wednesday Sessions
       Session VST-WeM

Paper VST-WeM7
Thermal Desorption Study of Austenitic Stainless Steels

Wednesday, October 31, 2001, 10:20 am, Room 125

Session: Gas Sorption Phenomena I
Presenter: P. Chiggiato, CERN, Switzerland
Authors: J.-P. Bacher, CERN, Switzerland
C. Benvenuti, CERN, Switzerland
P. Chiggiato, CERN, Switzerland
M.-P. Reinert, CERN, Switzerland
S. Sgobba, CERN, Switzerland
A.-M. Brass, Université Paris-Sud, France
Correspondent: Click to Email
Residual hydrogen in stainless steel results in a steady outgassing from vacuum chamber walls, hindering the achievement of UHV conditions. The total content, the binding states and the diffusivity of residual hydrogen in austenitic stainless steels, which together define the room temperature hydrogen outgassing rate, have been investigated by Thermal Desorption Spectroscopy (TDS). Eight different steel types have been studied by means of two different TDS systems. The study has been extended to the effects of various post-production treatments, aimed at reducing the hydrogen content and/or outgassing, namely vacuum firing and bakeout both in air and under vacuum. A large variety of hydrogen desorption peaks has been observed, which have been attributed to diffusible hydrogen, hydrogen trapping in the surface oxides or in lattice defects induced by precipitates, and steel recrystallisation. The hydrogen depletion effectiveness of vacuum baking at different temperatures has been quantified, and the consequences of air baking have been clarified, leading to practical guide-lines for technological applications.