Tribological performance and corrosion behavior of CoCrMo alloy

The present work focuses on the Tribological properties and corrosion behavior evaluation of sintered CoCrMo alloy. The CoCrMo alloy was elaborated by Powder metallurgy process at various sintering temperatures (1200°C, 1250°C and 1300°C). The structural properties were characterized by X-ray diffraction and scanning electron microscopy. The tribological characteristics were measured using a dry disc-ball tribometer. The corrosion behavior of the samples was studied using different electrochemical tests in a simulated physiological environment (Hank’s solution). The obtained results show that higher sintering temperatures have a positive impact on the tribological behavior as well as the corrosion resistance of CoCrMo alloys. The sintered samples at 1300°C showed a better resistance to friction wear and a lower corrosion rate.

Microstructural Characterization of Borided Co-Cr-Mo Alloy

This study involves the effect of boriding powder composition on the microstructure and hardness of a CoCrMo alloy borided in a solid medium using the powder pack method. To investigate the effect of boriding powder composition, two different commercial boriding agents, Ekabor-HM and Ekabor III, were thoroughly mixed with ferrosilicon powders to form the boriding media. The CoCrMo samples were tightly packed with the Ekabor-HM and Ekabor III boriding powders in stainless steel containers to minimize oxidation. The boriding process was carried out under atmospheric conditions for 9 h in an electrical resistance furnace preheated to 1223 K. X-ray diffraction (XRD) analyses revealed that the surfaces of the borided CoCrMo alloys consisted of a bilayer composed of CoB and Co2B phases and also contained minor amounts of CrB, Mo2B5, and Mo2B. The average thickness of the boride layer in the samples borided with Ekabor HM and Ekabor III powders was 28±4.1 μm and 21±2.3 μm, while the average hardness of the boride layer was 1752±5.3 HV0.1 and 1364±3.8 HV0.1, respectively.

Bio-tribological behavior of articular cartilage based on biological morphology

Artificial hemiarthroplasty is one of the effective methods for the treatment of hip joint diseases, but the wear failure of the interface between the hemi hip joint material and articular cartilage restricts the life of the prosthesis. Therefore, it is important to explore the damage mechanism between the interfaces to prolong the life of the prosthesis and improve the life quality of the prosthesis replacement. In this paper, the creep and bio-tribological properties of cartilage against PEEK, CoCrMo alloy, and ceramic were studied, and the tribological differences between “hard–soft” and “soft–soft” contact were analyzed based on biomorphology. The results showed that with the increase of time in vitro, the thickness of the cartilage membrane decreased, the surface damage was aggravated, and the anti-creep ability of cartilage was weakened. Second, the creep resistance of the soft–soft contact pair was better than that of the hard–soft contact pair. Also, the greater the load and the longer the wear time, the more serious the cartilage damage. Among the three friction pairs, the cartilage in PEEK/articular cartilage was the least damaged, followed by CoCrMo alloy/articular cartilage, and the most damage was found in ceramic/articular, indicating that the soft–soft friction pair inflicted the least damage to the cartilage.