Titanium plasma nitriding intensified by thermionic emission source

摘要

The present invention relates to ion nitriding of pure titanium or titanium-containing alloys at low pressure by intensifying the glow discharge.PPPlasma intensification was produced by thermionic emission in conjunction with a triode glow discharge system. Effective ion nitriding can be achieved by employing the present invention at relatively low temperatures (480° C.) and with significantly enhanced compound layer growth kinetics compared to the conventional nitriding techniques. Processed Ti and Ti-6Al-4V developed a surface layer of TiN followed by a Ti.sub.2 N layer and an interstitial nitrogen diffusion zone. Processed specimens showed a three fold increase in surface hardness. Surface roughness was found to be a function of the degree of plasma intensification. Processing of Ti-6Al-4V resulted in a higher wear, corrosion and wear-corrosion resistance. The present invention indicates that ion nitriding with intensified glow discharge has a great potential as a surface modification method for Ti and Ti alloys. Materials nitriding by the present invention having the properties defined above are suitable for use as orthopaedic implant devices as well as other applications of titanium and titanium alloys requiring resistance to wear and corrosion.