Corrosion performance of medical grade NiTi after laser processing

Laser processing of shape memory alloys (SMAs) has great potential to enable the multi-functionality required for complex applications. Achieving this improved functionality often requires laser processing of the SMA's with a high-energy pulse coupled with an observable decrease in the corrosion resistance, however there are discrepancies in the post-processing corrosion performance. The current study conducts a systematic investigation of Ni-44.2wt% Ti SMA with differing numbers of laser pulses and post-process surface treatments. The localized electrochemical characteristics were investigated by scanning electrochemical microscopy. X-ray photoelectron spectroscopy and Raman spectroscopy was used to determine surface composition and oxide crystallinity, while oxide stability was determined via potentiodynamic cyclic polarization. Results showed that fewer pulses were not significantly detrimental to the corrosion performance. However, increasing the number of pulses had a significant impact on oxide stability in the heat affected zone due to increased crystallinity. The post-process surface treatments restored corrosion performance to pre-processed capabilities; however, further optimization is required to achieve maximum corrosion resistance.