TRIBOCORROSION STUDIES ON SURFACE MODIFIED MEDICAL GRADE STAINLESS STEEL

摘要

Tribocorrosion performance of medical grade AISI 316L stainless steel with and without surface modification has been studied during exposure to an electrolyte. Some of the samples investigated were surface modified by plasma nitriding (at both 400 and 550 °C), and others by a special arc physical vapor deposition to secure a thin layer of a diamond-like carbon (DLC) coating on the surface of the samples. XRD and SEM were used to characterize the homogeneity and microstructure of all samples. Potentiodynamic polarization measurement and tribocorrosion tests were performed multiple times on all groups of samples. It was established that surface treated SS 316L exhibited totally different passive behaviors, which consequently lead different tribocorrosion performance in the electrolyte. It was also established that the DLC coating performed as a solid lubricant in the ball-on-plate tests, and the resulting wear track after the tribocorrosion tests was almost negligible. On the other hand, the untreated and Nitriding 400 °C samples experienced wear accelerated corrosion due to their passive behavior. The results suggest that the DLC coated SS 316L have the best performance at the combined wear and corrosion environment, while the untreated and Nitriding 400 °C samples should be avoided to apply in biological tribocorrosion conditions.