Influence of Laser Marking on Microstructure and Corrosion Performance of Martensitic Stainless Steel Surfaces for Biomedical Applications

Abstract

Abstract The medical device industry demands unique device identification (UDI) tags on metallic components applied via laser marking. A common issue is that the visual appearance of the marking becomes poorly legible over time due to loss of contrast. Nanosecond pulsed laser irradiation was used to grow an oxide layer on two different martensitic stainless steels AISI 420F mod and 420B to compare the influences of the chemical composition of the steel (with and without S), power density, and energy input. The corrosion behavior was found to depend strongly on laser energy input. The presence of sulfur negatively affected the corrosion resistance and narrowed the applicable window for the laser processing parameters significantly. For the sulfur-containing AISI 420F steel, 3‒5 μm wide craters formed on the surface after laser marking, which is interpreted as thermal degradation of protruding MnS inclusions resulting from the laser marking process. Also, substantial cracking in the oxide layer was observed. The marked specimens suffered from corrosion in a thin zone below the formed oxide layer. This behavior is attributed to Cr-depletion in the zone adjacent to the oxide layer, resulting from providing Cr to the growing oxide layer.