Improving the resistance to sliding contact damage of zirconia using elastic gradients

Zirconia-based ceramics with high strength have been identified as a material of choice for sliding components in a variety of biomedical and engineering applications. Despite the high flexural strength, zirconia prostheses are still vulnerable to wear and surface damage. We hypothesize that such tribological damage may be substantially mitigated by an engineered grading of elastic modulus at the ceramic surface. In this study, graded structures were fabricated by infiltrating glass into the top and bottom surfaces of zirconia plates, with resulting diminished modulus in the outer surfaces. The plates were then subjected to frictional sliding tests using a hard spherical indenter. Compared with noninfiltrated controls, infiltrated specimens showed a significant increase in the fracture loads, by over a factor of 3. The increase in the sliding contact resistance is attributed to the diminishing tensile stresses at the graded lower modulus surface. The results confirm that suitably graded structures can be highly beneficial in the design of next-generation orthopedic and dental prostheses.