CoCrMo alloys are often used as the material for metal artificial joint because of their high corrosion resistance and mechanical properties. In this study CoCrMo alloys having different palladium amount of produced by investment casting method. Scanning electron microscopy, X-ray diffraction method and indentation tests were used to examine the mechanical properties of the alloys. Indentation experiments were carried out using Vickers indenter that the loads range from 0.245 to 9.8 N. The alloys exhibit significant load-dependence (i.e., indentation size effect). Meyer's law, proportional specimen resistance model, and Hays-Kendall model were used to analyze the load dependence of the hardness. As a results for load-independent determination of the CoCrMo alloys, the Hays-Kendall model is found to be more effective than the proportional specimen resistance model and microhardness values decreases with increase of the Pd content.

CoCrMo alloys are one of the most commonly used materials for hip arthroplasty, knee and dental because of its mechanical properties, corrosion resistance, wear resistance and biocompatibility. In this study, CoCrMo alloys consisting of 1.68 to 4.33%Pd are produced by investment casting process under argon atmosphere. The microstructures and mechanical properties of CoCrMo alloy were studied using X-ray diffraction, optical microscopy, scanning electron microscopy, Knoop indentation hardness tests, focusing on the influences on the different palladium additives. The measured microhardness values of CoCrMo alloys having different palladium ratio are seen to be load-dependent. The observed load dependence was rationalized using the Hays-Kendall model and it was found that the resultant load-independent hardness decreases with increase of palladium ratios. As a results, microhardness decreases with increase of palladium amount.