Development and biocompatibility of hard Ti-based coatings using plasma immersion ion implantation assisted deposition

The hard Ti-based coating TiAlN has been produced by plasma immersion ion implantation-assisted deposition (PIIIAD) on austenitic stainless steel. 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 renders alternate phases of deposition (during the bias off time) and implantation and deposition (during bias on time), thereby controlling deposition temperature, reduction of compressive stresses, increase of crystallinity and enhancing adhesion of coating to substrate. The deposition has been carried out in a neutral as well as reactive nitrogen environment, which leads to nitrogen-containing coatings. In addition to TiAlN, also, Ti, TiN and TiAl were produced to investigate the effect of the different elements. All the coatings are tested for their suitability as biocompatible coatings, and hence, the adherence of osteoblast progenitor cells to these coatings was investigated in correlation with deposition parameters and surface morphology. The results identify the coatings that are wear resistant and suitable for orthopaedic implants.