Enhancement of corrosion resistance, hardness, and biosafety for martensitic stainless steel via laser thermal processing

A laser thermal processing technique was used to efficiently improve the corrosion resistance of 420J2 martensitic stainless steel. The top layer of the steel plate was melted and immediately solidified by properly controlled laser irradiation. After the processing, the surfaces of the specimens were oxidized. The roughened oxidized layer that formed on the as-processed specimen was removed by grinding to expose the remelted layer. Potentiodynamic anodic polarization measurements confirmed that the remelted layer showed much better corrosion resistance. Furthermore, the hardness of the remelted layer increased to 700 HV. To evaluate the initial cell activity of the processed steel, osteoblast-like cell line (MC3T3-E1) was used. The initial proliferation of the cells was significantly improved on the laser-processed stainless steel. Therefore, laser thermal processing is a useful tool for developing novel materials with a combination of hardness, corrosion resistance, and cytocompatibility.