レーザマーキングが医療用チタン合金の微細組織に及ぼす影響

抄録

To thoroughly manage information such as medical accident and Product Liability Act, medical products are obliged to display product number directly. Main indication methods are marking using laser. However, fracture with the laser marking part as a starting point has been reported. Laser marking parts which are subjected to thermal influences can be inferred to locally change the surface texture, microstructure, and mechanical properties, but their investigation has not been done sufficiently. In this study, continuous laser irradiation was applied to medical titanium alloys. The laser irradiated surface and cross section was observed in detail using a scanning electron microscope (SEM). With respect to the cross section, polishing was sequentially performed from emery paper #800 to #4000, then mirror-finished using Al₂O₃ particles (0.3μm) and subjected to etching treatment. The quantitative ratio of α phase and β phase in the heat affected zone of the laser irradiated part was analyzed by electron backscatter diffraction (EBSD) method. As a result, the height of the laser-irradiated surface was reduced by dissolution. On the other hand, the end of the irradiation trace width was raised by solidification. Also, the amount of oxygen on the surface oxidized at high temperature by laser irradiation increased and the hardness increased. In addition, the crystal structure (α+β) was changed by laser irradiation from the observation of the microstructure of the cross section of the laser irradiation part.