Development of Ti based coatings using plasma immersion ion implantation assisted deposition techniques and their properties

Various Ti based coatings have been produced by plasma immersion ion implantation assisted deposition (PIIIAD) technique on a wide variety of substrates. In PIIIAD, the substrate is exposed to cathodic arc plasma comprising of metallic ions corresponding to the cathode composition, and the substrate is biased pulsed negative. The pulsed bias of the substrate gives alternate phases of deposition (during the bias off time) and implantation and deposition (during bias on time). Thus the deposition temperature can be controlled and simultaneously the compressive stress can be reduced, enhancing adhesion of the coating with the substrate. The deposition has been carried out in a neutral as well as reactive nitrogen environment, which leads to nitrogen bearing coatings. The coatings investigated are Ti, TiN, TiAl, TiAlN. It has been observed that the TiAl composition on the substrate depends on the bias and is different from the cathode composition. TiN and TiAlN coatings are hard coatings and show an enhanced wear resistance. All the coatings are tested for their suitability as biocompatible coatings on stainless steel substrates, and hence the adherence of osteoblast progenitor cells to these coatings was investigated in correlation with deposition parameters and surface morphology. The results indicate that these coatings can suitably be used as inert wear resistant coatings for orthopaedic implants.