Thermal desorption from stailess steel sample coated with TiN and oxide layers

The effectiveness of some different kinds of surface coatings on austenitic stainless steel samples is discussed on the basis of their effects on the outgassing flowrates in vacuum and at high temperature. Special attention is given to the reduction of molecular hydrogen diffusion from the bulk. The effects of TiN thin films and oxide layer were studied through total and partial pressure measurements in a known-conductance system in which the dynamic method is applied; gas analysis was performed by a mass spectrometer, using the TDS technique (Thermal Desorption Spectroscopy). The results show that TiN thin films can produce a drastic reduction of the total outgassing flowrate from stainless steel (more than 50%); in the particular case of the oxide layer there is even a 70% reduction in comparison with the case of simply polished stainless steel. As far as hydrogen outgassing flowrate, the decrease is equal to about 80% in the case of TiN thin films and to 90% in the case of oxide coating.