Bulk metallic glasses (BMG) for biomedical applications—A tribocorrosion investigation of Zr55Cu30Ni5Al10 in simulated body fluid

The acceptability of implants by the human body is a very important requirement in the field of biomaterials. Implants should not cause diseases or other complications to the patients. Further, biomaterials should possess enough mechanical strength, corrosion and wear resistance in order to withstand the harsh conditions of the body environment. If this is not achieved, degradation of the implant occurs and secondary effects take place leading to carcinogenicity, hypersensitivity and inflammation. In the present work a new alloy composition (bulk metallic glass) as potential biomaterial for implant bearing material has been studied. The bulk metallic glass (BMG) is a disordered solid without the long-range order of crystalline materials. This characteristic makes them free of defects such as grain boundaries, dislocations and voids. Knowledge regarding their electrochemical and tribocorrosion performance is very limited. Thus, the assessment of metallic glasses as potentially applicable in situations where wear and corrosion act simultaneously is still premature. The electrochemical and tribocorrosion performance of a Zr-based BMG has been evaluated in different solutions with and without the presence of protein. The results show that the BMG material with amorphous structure has the largest wear rates in all electrolytes tested (NaCl, phosphate buffer solution and phosphate buffer solution with protein). This is due to the passivation character of the alloy leading to wear accelerated corrosion. The amorphous structure of the alloy promotes the formation of an amorphous oxide film. On the other hand, the crystalline structure of the BMG shows negligible wear rate due to a nanocrystallization process or the presence of a new phase (Zr2Cu) leading to lack of passivation and thus minimizing wear accelerated corrosion.