Bio-tribological response of duplex surface engineered SS316L for hip-implant application

Here we report on intelligently planned duplex surface engineering concept that utilizes a combination of plasma nitriding and multi-layering for optimizing cyclic fatigue resistance. This new concept of duplex surface engineering treatment is utilized to achieve improvement in cyclic fatigue as well as bio-tribological response of SS316L (SS) based hip-implants. The samples are SS316L (SS), Ti/TiN multi-layer-coated SS i.e., SSML and Ti/TiN multi-layer-coated plasma nitrided SS i.e., SSPNML. The samples are characterized by XRD, FESEM, TEM, nanoindentation, micro-scratch and sliding wear. In addition, cyclic fatigue behaviour up to 1 million cycles of SS and SSPNML femur heads against UHMWPE acetabular cups are studied using a hip simulator. The results prove that under comparable conditions, the nanohardness, micro-scratch resistance and sliding wear resistance of the SSPNML samples in SBF are much better than those of the corresponding SSML and SS samples. Further, as compared to the SS femoral head, the SSPNML femoral head is found to be much more resistant to cyclic fatigue. These results establish beyond doubt the superiority of the duplex surface engineering treatment utilized in the present work to achieve superb cyclic fatigue resistance in SS based femoral heads for bio-prosthetic hip implants.