Tribological Characterization of AlCrN, AlTiN, AlTiON, and AlCrON Coatings on CoCrMo Alloy

CoCrMo alloys are commonly used in artificial joints. However, tribocorrosion phenomena have led to the search for improvements to diminish wear debris and ion release. Engineering of surfaces is an alternative to achieve this purpose. In the present study the tribological effect of AlCrN, AlTiN, AlTiON, and AlCrON coatings deposited on cast CoCr alloy was investigated. The coatings were deposited by the physical vapor deposition (PVD) sputtering technique. Adhesion of the coatings was determined with a scratch tester by identifying critical loads at different failure levels. A ball-on-disc tribometer was used to assess the wear behavior using Ringer's solution as the lubricant. Samples were characterized with metallographic techniques, scanning electronic microscopy (SEM), profilometry to measure roughness (R-a ) and wear, and microhardness tests. In the AlTiON and AlCrON coatings the porosity was diminished and the hardness increased due to the presence of oxygen. However, the tribological performance was poor. The AlTiN coating exhibited high adherence and wear resistance even though it also presented the lowest hardness.