THE INFLUENCE OF A GLOW-DISCHARGE TREATMENT ON SURFACE MODIFICATION AND OUTGASSING RATE OF STAINLESS-STEEL AND TITANIUM-ALLOYS

The aim of these investigations is to characterize surfaces of metalli c samples modified by different discharge techniques. Outgassing measu rements were carried out and the results were correlated with the resu lts of chemical surface analyses. In first experiments the influence o f an ac gas discharge on the outgassing rates of titanium alloys was s tudied. It was shown that the applied discharge technique had nearly n o influence on the outgassing rate of these alloys. Furthermore we exp osed stainless steel samples to electrons, argon and oxygen ions eithe r in a de glow discharge or ina microwave discharge. If was found that the de glow discharge in an Ar/O-2 mixture had the strongest effect o n the reduction of the outgassing rate in comparison to the other plas ma treatments. The surfaces of the treated samples were investigated w ith respect to the topography and the chemical composition (depth prof ile) by SEM, AES and XPS. At the treatment parameters chosen, the inco rporation of oxygen by the de glow discharge is much more effective in comparison to microwave discharge. It was verified that an oxidation of Fe and Cr appeared under this reactive plasma treatment up to a dep th of 15 nm.