Modification of biomedical NiTi shape memory alloy by TiC/Ti films using PIIID

TiC/Ti coatings were deposited on the surface of Ti-50.6 at.% Ni alloy by plasma immersion ion implantation and deposition (PIIID) technique. The microstructure, mechanical properties and hemocompatibility of the samples were investigated by means of XRD, AFM, nanoindentation, and scratch and platelet adhesion tests. The result of XRD analysis shows that the crystalline TiC coating has a preferential orientation of (111) in the normal direction. The surface presents a very smooth and dense microstructure with 1.517 nm root mean square roughness (RMS). The average hardness and modulus values of the TiC coating are much higher than those of the NiTi substrate. In the initial stage of scratching, some obvious transversal cracks and worm-like cracks spreading into the film from both side of the scratch track were observed. At higher normal loads for the scratching test, the film delaminated from the substrate at the margins of the substrate. Platelet adhesion tests demonstrate that the hemocompatibility of the coated sample is improved.