NANOMECHANICAL CHARACTERIZATION OF ZIRCONIA THIN FILMS DEPOSITED ON UHMWPE BY PULSED PLASMA DEPOSITION

Plastic deformation and wear of the ultra-high molecular weight polyethylene (UHMWPE) insert have been pointed out as major issues relating to the long-term stability of an orthopaedic implant. The deposition of protective hard, tough and well-adhered zirconia (ZrO2) thin films directly on the surface of the UHMWPE component via the Pulsed Plasma Deposition (PPD) technique has been already demonstrated to be a feasible way to approach this problem. In the current study, the tribo-mechanical properties of ZrO2-coated UHMWPE with respect to pristine UHMWPE were investigated in detail. Specifically, strength to local plastic deformation, indentation work portioning and creep behavior were evaluated through nanoindentation and micro-scratch tests. Further, preliminary wear data (i.e., rate and volume) were obtained by tribology tests mating coated and pristine UHMWPE with an alumina ball under dry conditions. The results of the mechanical tests evidenced a strong reduction of plastic deformation under both normal and tangential local loads and a drop of the 80% of the creep phenomenon for coated UHMWPE compared to pristine UHMWPE. Despite tribological tests showed similar wear data for coated and pristine UHMWPE, a different wear mechanism was detected between the two groups. The reported results supported the possibility to pursue this novel approach of depositing ZrO2 thin film to protect the UHWMPE insert and enhance the long-term stability of the orthopaedic implants.