CHARACTERIZATION OF THE RESISTANCE OF PYROLYTIC CARBON TO ABRASIVE WEAR

Si-alloyed pyrolitic carbon (PyC) is currently employed in many biomed ical devices, due to its fairly good biological compatibility and non biodegradeability. For prosthetic heart valve applications, required t o operate safely for many years, the resistance to abrasive wear is on e of the limiting factors which must be accurately evaluated. The pres ent study reports on abrasive wear testing of Ti/PyC and PyC/PyC slidi ng couples. For both couples it was found that the wear behaviour can be shifted from a low wear regime, characterised by very small wear ra tes and reduced scatter, to a high wear regime, characterised by high wear rates and high scatter, due to the presence of particle contamina tion coming from the environment and/or from the specimen polishing pr ocess. Actual biomedical devices, particularly heart valves, should no t experience the high wear regime, due to the absence of any hard part icle contamination source. The wear observed in these items is in fact minimal and may depend on mechanisms other than abrasive wear. In the se conditions the experimental evaluation of the wear behaviour should definetely be performed by tests on actual devices.