Wear studies on plasma sprayed Al_2O_3-40 wt% 8YSZ composite ceramic coating on Ti-6Al-4V alloy used for biomedical applications

摘要

The relative wear resistance of three candidate coatings for titanium alloy-based orthopedic applications was compared using a reciprocating test method. Micrometer-sized powders of the following compositions were plasma sprayed onto Ti-6Al-4V (TAV) alloy: (i) Al_2O_3 (AO), (ii) 8 mol% yttria stabilized zirconia (8YSZ) and (iii) Al_2O_3-40 wt% 8YSZ (A4Z). Deposits were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and porosity measurements. In addition, microindentation hardness measurements and scratch-based adhesive/cohesive strength measurements were also performed. The composite coating (A4Z) had superior wear resistance. Wear track examination suggests two reasons for this improvement. First, the A4Z coating had improved cohesive strength between splats, and second, there was a phase transition toughening mechanism associated with tetragonal zirconia. Results of contact mechanics calculations support the experimental findings.