工業用純チタンの腐食挙動に及ぼすN₂⁺イオン注入の影響

抄録

N₂⁺ ions were implanted into commercially supplied pure titanium with different doses ranging from 5×10¹⁶ to 1×10¹⁸ions/cm², and the corrosion behavior was investigated in 70% sulphuric acid solution. Anodic polarization curves show that the peak anodic current density, passivation current density, and corrosion potential increase with increase in implantation dose when the dose is less than 1×10¹⁷ions/cm². When the implanted dose is 5×10¹⁷ions/cm², the corrosion resistance decreases though it is still larger than no implanted titanium. X-ray diffraction analysis shows the formation of titanium nitride on the implanted surface, i.e., Ti₂N is found when the implanted dose is larger than 5×10¹⁶ions/cm² and both Ti₂N and TiN when the implanted dose is 1×10¹⁸ions/cm². The aging at 673K after ion implantation largely increases the corrosion resistance, which corresponds to the enhanced precipitation of Ti₂N and TiN. AFM observation shows fine particles of titanium nitrides on the implanted surface. It is considered that the precipitation of Ti₂N or TiN decreases the effective corrosion area to make the corrosion resistance higher.