During the last few years there has been a renewed interest on the use of metal-on-metal (MOM), as well as ceramic-on- metal (COM), total hip replacement implants. However,concerns related to metal debris generation and metal ions release, as a result of mechanicalwear and wear-enhanced corrosion, still arise. This directly affects the durability of metallicimplants in vivo, where material degradation predominantly occurs through the combinedaction of wear and corrosion, a process termed tribocorrosion.
One metallic biomaterial isbiomedical grade 316LVM stainless steel which exhibits an excellent corrosion resistanceowing to a self-healing nanometric passive film. Nonetheless, its tribocorrosion performanceis poor, greatly limiting its application. As an attempt to reduce metal debris and release ofmetal ions, two surface treatments were carried out on untreated 316LVM stainless steel(denoted ‘U/T S.S.’); a carburised 316LVM stainless steel (denoted ‘Carburised S.S.
‘)prepared via low temperature carburising which created a carbon diffused layer (known as ‘S-phase’) and a duplex PVD coating, a carburised stainless steel followed by a CoCrMo(C)layer which was subsequently followed by a CrN layer (denoted ‘CrN/S/Carburised’),prepared via magnetron sputtering. Both surface treatments displayed a higher hardness and ahigher mechanical wear resistance than the U/T S.S. The surface treated samples also showeda good corrosion resistance in full strength Ringer’s solution during potentiodynamic testing.The tribocorrosion behaviour of all samples was investigated in full strength Ringer’ssolution at 37 ± 1 o C using a reciprocating sliding tribometer with an alumina (?-Al 2 O 3 )counter-material with an integrated electrochemical cell. Open circuit potential (OCP) andpotentiostatic tests were carried out to explore the mechanical and chemical contributions tothe overall material loss as well as to scrutinize the behaviour and endurance of the surfaceengineered layers. Results showed that the surface treatments inhibited material loss anddisplayed low coefficient of friction.
The duplex treated CrN/S/Carburised was very effectivein reducing the total material loss under all electrochemical conditions, indicating a superiortribocorrosion performance than the other samples. Carburised S.S.
showed a fairly bettertribocorrosion performance under OCP and anodic potentials as opposed to U/T S.S. but onlydisplayed a 12% improvement under cathodic potential conditions.