ON THE TRIBOLOGICAL PERFORMANCE OF HARD ON HARD THR COMBINATIONS

The evaluation of the historically decreasing wear data for ceramic on ceramic and metal on metal combinations is mostly restricted to quantitative measuring methods describing material loss with increasing limitations. For example an about factor 10 improvement for a current quality of a hot isostatically pressed alumina compared to earlier non-hipped alumina materials can be derived from estimations of profilomertical and gravimertical wear data in laboratory tests. Just after the first million of cycles in the joint simulator the detection limits of these methods result “no measurable wear”. In contrast, SEM and EDX show still distinct wear phenomena and in case of metal components additionally a variety of tribochemical reaction products and layers. Otherwise preliminary wear particle characterisations of ceramic debris from the simulator lubricant raise the expectation of a reduction of wear induced limitations of the functional life of total hip replacements. As to the wear performance of 57 collected ceramic retrieval couples the means for a pre-clinical validation seem unsatisfactory. The methods measuring wear directly still seem not to be able to enter a standard on the wear evaluation of hard on hard combinations made of currently available materials.