Micro-abrasion/Corrosion Behavior of Pack-Borided AISI 316L Steel and ASTM F1537 CoCrMo Alloy in Ceramic-on-Ceramic Couplings

This study aims to investigate the effect of the presence of a simulated corrosive body fluid (Hank’s solution) on the micro-abrasion and corrosion resistance of two borided biomedical alloys (AISI 316L stainless steel and ASTM F1537 CoCrMo alloy) when in sliding contact with a ceramic countersurface. The materials were subjected to a powder-pack boriding treatment. The modified surfaces were characterized mechanically and physico-chemically. The changes of wear resistance of both borided alloys were determined by means of micro-abrasion tests using a slurry made of the corrosive solution with F-1200 SiC abrasive particles. 25-mm-diameter dielectric glass balls were used as countersurface in the wear tests with the twofold purpose of replicating a ceramic-on-ceramic biomedical contact and avoiding the effect of galvanic corrosion with the metallic samples to be tested. The tests were run in triplicated at 0.1, 0.2 and 0.5N of applied load at constant sliding distance and speed. The wear volumes and wear scar examination were carried out by optical profilometry and microscopy. On the other hand, the corrosion resistance of the materials (before and after boriding treatment) was characterized by potentiodynamic polarization measurements in a closed three-electrode cell using the corrosive fluid. According to the results found, the hardness of the alloys increased significantly between 300 and 400% by boriding. However, the micro-abrasion/corrosion situation was detrimental for both alloys under sliding with the ceramic countersurface in the presence of Hank’s solution, which is opposite to that reported in literature for other abrasion–corrosion conditions investigated.