The sintering kinetics of CoCrMo powders is investigated by dilatometry. Pre-alloyed spherical powders were axially compacted and sintered between 1300°C and 1375°C. SEM images coupled to an EDS analysis are used to assess the microstructure of sintered samples. Microhardness of the sintered samples was also evaluated. Densification is carried out in both solid and semi-solid states. The final densification is dominated by the appearance of liquid, which fills the remaining pores. The dominant diffusion mechanisms are volume diffusion and viscous flux diffusion for the intermediate and last stages of sintering. Hardness increased as the temperature did it, too. Intermetallic compounds formed due to the liquid reaction were determined to be reached in molybdenum. The increment in hardness is attributed to densification and stresses generated by the solidification of eutectic liquid. It is concluded that the sintering of CoCrMo powders should performed between 1350 and 1375°C to obtain better mechanical properties.

This study investigates the impact of in situ boron reinforcement on a biocompatible Ti-30Zr-10Ta alloy produced by powder metallurgy for biomedical applications. This research focused on understanding the influence of boron content (0 to 5 wt.%) on the microstructure, mechanical properties, and tribological behavior of the alloy. The main results showed that increasing boron additions progressively decreased the relative density of the sintered samples. Microstructural analysis via X-ray diffraction (XRD) revealed that the base Ti-30Zr-10Ta alloy exhibited a dominant β-Ti phase with the presence of orthorhombic α″ martensite. The addition of boron led to the in situ precipitation of various borides, specifically TiB, TiB₂, TaB, and TaB₂. Further characterization revealed that the microhardness was enhanced up to 19.6% with lower boron additions, maintaining the elastic modulus of the alloys. Tribological tests demonstrated a significant improvement of 25.7% in wear resistance because of the reinforcement with lower amounts of boride particles. However, higher amounts of boron resulted in a reduction in hardness and elastic modulus at the surface level of 47.2 and 49.3%, respectively, an increase in porosity, and the formation of three-body particles, which contributed to more severe wear and decreased more than twice the wear resistance of the alloy. This research successfully determined the threshold value in a maximum of 0.5 wt.% of boron additions for in situ reinforcement of a biocompatible Ti-30Zr-10Ta alloy suitable for load-bearing applications.

This study aims to develop CoCrMo/xCu composites through liquid phase sintering. The primary focus is on investigating how the addition of copper influences sintering kinetics, microstructure, and mechanical properties. The copper volume fraction ranged from 10 to 25 wt.% relative to CoCrMo. Sintering was conducted at 1150 °C under an argon atmosphere. Characterization methods included scanning electron microscopy, computed microtomography, and X-ray diffraction analysis. It was observed that molten copper, which forms upon reaching its melting temperature, can fill the interparticle spaces left by CoCrMo particles in the green compacts. During sintering, densification is further enhanced by the dissolution of CoCrMo, resulting in the formation of intermetallic phases enriched in Cr and Mo, as well as a ternary Co-Cr-Cu compound. Both densification and intermetallic formation contribute to increased microhardness as Cu content rises. It is concluded that the CoCrMo/25Cu composite exhibits the best mechanical and corrosion properties because its densification was improved by the Cu liquid.