A fast, stepwise procedure to assess time-temperature equivalence for hydrothermal ageing of zirconia-based materials

Hydrothermal ageing is one lifetime-limiting phenomenon of zirconia-based ceramics and composites for many applications, from biomedical implants to ferrules and watches. Predicting hydrothermal ageing at use-temperature implies a set of accelerated ageing experiments conducted under water vapour at several, high temperatures (usually between 100°C and 140°C). From these data, the activation energy of ageing can be determined, and thus ageing can be predicted at any temperature. However, obtaining precise extrapolations with this procedure requires the use of lower temperatures (70 or 80°C), leading to a rather long procedure (up to a few thousand hours), and should involve at least one specimen for each test temperature. This article presents a new procedure that allows the determination of all ageing parameters and the estimation of kinetics at use-temperatures with the use of a single specimen within a shorter time, accurate enough for fast screening of new materials.