Plasma surface modification of NiTi shape memory alloy

NiTi shape memory alloys are very attractive for orthopaedic and orthodontic implants. However, micro-motion-induced wear and the potential release of toxic ions into the body are major concerns for such applications. In this study, Ti49Ni51 samples were plasma surface alloyed in air at 400 and 500 degrees C. The modified surfaces were characterised by glow discharge spectrometer (GDS), XRD, SEM, scratch and nano-hardness tester. The wear and corrosion properties of the plasma surface alloyed NiTi samples were evaluated, respectively, by a pin-on-disc tribometer under un-lubricated conditions and by anodic polarisation tests in Ring's physiological solution. The experimental results have shown that the PSA treatment can convert the original surface into a TiO2 layer, thus reducing the Ni content in the surface. The surface hardness of the Ti49Ni51 alloy increased from 4.6 GPa to 23.0 GPa following the PSA treatment, and the sliding wear resistance of all the treated samples has been effectively increased. (c) 2006 Elsevier B.V All rights reserved.