Influence of laser surface modification on corrosion behavior of stainless steel 316L and Ti-6Al-4V in simulated biofluid

Laser surface engineering has been explored as a possible method for improving the functional surface properties of biomedical materials such as stainless steels and titanium alloys. This study emphasises the influence of laser surface processing, carried out at a range of laser powers from 500 to 1500 W in ambient atmosphere, on the surface microstructure and corrosion behaviour of stainless steel 316L (SS316L) and Ti-6Al-4V, and metal ions released during the corrosion process. A homogeneous surface microstructure includes columnar dendrites and fine grains in the resolidified region of SS316L. A gradual increase in grain size from the processed surface towards the substrate was revealed. The laser processing of Ti-6Al-4V produced a surface full of dendrites followed by acicular martensite in the interface region. The corrosion studies in Ringer's physiological solution showed an increase in the open circuit potential (OCP) as a result of laser surface treatment of both SS316L and Ti-6Al-4V (more noble than untreated). After laser processing, the corrosion properties of SS316L were seen to deteriorate, and those of Ti-6Al-4V to improve, as compared to their respective untreated counterparts. The variation of laser power influenced the corrosion resistance of SS316L, while that of Ti-6Al-4V did not vary significantly. Laser surface treatments at higher powers (>1000 W) reduced the leaching of specific metallic ions from SS316L and Ti-6Al-4V during corrosion in Ringer's physiological solution.