Impact of Chromium and Molybdenum Content On Cobalt-Based Alloys

Cobalt chromium molybdenum alloy systems are widely used in orthopedic implants due to their excellent metallic properties. However, their practical applicability is severely hampered by the inability to maintain mechanical and tribological properties without compromising corrosion resistance.

Impact of Chromium and Molybdenum Content On Cobalt-Based Alloys​​​​​​​

​​​​​​​Study: Effect of chromium and molybdenum increment on the crystal structure, nanoindentation and corrosion properties of cobalt based alloys. Image Credit: RHJPhtotos/Shutterstock.com

An accepted paper from the journal Physica Status Solidi A tackles this issue by investigating the impact of chromium and molybdenum concentration in a cobalt chromium molybdenum alloy system. The study mainly focused on the structural, physicochemical, and nanoindentation characteristics of the cobalt chromium molybdenum alloy systems.

Cobalt-Chromium Molybdenum Alloys: Overview and Significance

Many research groups are currently focused on creating new alloys and metals that can enhance the effectiveness of orthopedic implants, notably in young and more active patients.

Cobalt chromium molybdenum alloy systems are a significant alloy group in this regard because of their exceptional physical reliability, wear effectiveness and corrosion resistance.

While ASTM guidelines limit the alloy configurations for cobalt chromium molybdenum alloy systems, they also provide compositional regions within which a variety of alloy configurations with distinct nanostructures and phase makeups can be obtained. This allows for customizable mechanical, nanoindentation, and electrical properties of cobalt chromium molybdenum alloy systems.

Properties of Cobalt Chromium Molybdenum Alloy Systems

The physical and rheological characteristics of cobalt chromium molybdenum alloy systems are derived from the alloys' crystalline structure and metallurgical morphology, both of which are determined by the alloy compositions.

Carbon is a critical component in cobalt chromium molybdenum alloy systems. While carbon is insoluble in pure cobalt, it can produce carbides with chromium and molybdenum that function as crystallites inside the substrate, preventing dislocation slippage.

These carbides can help to reinforce cobalt chromium molybdenum alloys, although their effect on rheological effectiveness differs depending on how the alloy is treated. The treatment procedures have an effect on the shape, content, dispersion, and size distribution of the carbides within the substrate, which in turn affects the efficiency of the cobalt chromium molybdenum alloy systems.

Crystalline Nature of Cobalt Chromium Molybdenum Alloy Systems

Cobalt, chromium, and molybdenum can coexist as a singular stable mixture in the face-centered cubic (FCC) or hexagonal-close packed (HCP) phase. Pure cobalt undergoes the transformation from FCC to HCP phase at 417 degrees Celsius. However, the transition temperature rises when it is coupled with an HCP chromium and molybdenum alloy.

The FCC state in these materials has enhanced flexibility and elastic modulus, but the alloy's low lattice distortion energy restricts dislocation cross-slip. This causes extensive stacking defects in the cobalt chromium molybdenum alloy, allowing for the strain-induced change to the HCP phase.

These modifications improve the alloy's tribological properties. It not only results in a tougher cobalt chromium molybdenum alloy surface, but the friction factor produced from single crystals HCP alloy is roughly 50% less than that acquired from FCC alloy under identical conditions and sliding speed.

Highlights and Key Developments of the Current Study

Pure cobalt is volatile and susceptible to corrosion attacks when employed in chloride-rich settings. Chromium prevents this volatility by creating an enhanced passive oxide film on the alloy interface. Including molybdenum in the shape of oxides or metals further supports the passive effect.

Although chromium, cobalt, and molybdenum are required for specific metabolic functions in the human body, any increase over a certain level is considered undesirable owing to probable inflammation responses.

Since the content of the cobalt chromium molybdenum system is crucial in determining its characteristics, the researchers in this study concentrated on the production of diverse alloy compositions.

X-ray diffraction was used to investigate the impact on the crystalline structure. Moreover, an attempt was made to determine the optimal cobalt chromium molybdenum alloy content with better corrosion and mechanical characteristics.

The toughness of the cobalt chromium molybdenum alloy increased linearly as the chromium percentage increased. The open circuit voltage, linear sweep potentiometry, and polarization resistance measurements revealed that adding chromium to 30 wt.% increased the passivity of cobalt chromium molybdenum alloy systems, with any subsequent increase producing a deterioration in corrosion characteristics.

Based on these findings, it is reasonable to assume that the cobalt chromium molybdenum alloy investigated in this study has good potential for use in many orthopedic applications, provided the concentration of the alloy contents is carefully regulated.

Reference

Lone, S. A. et al. (2022). Effect of chromium and molybdenum increment on the crystal structure, nanoindentation, and corrosion properties of cobalt-based alloys. Phys. Status Solidi A. Available at: https://onlinelibrary.wiley.com/doi/10.1002/pssa.202200373

Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.

Hussain Ahmed

Written by

Hussain Ahmed

Hussain graduated from Institute of Space Technology, Islamabad with Bachelors in Aerospace Engineering. During his studies, he worked on several research projects related to Aerospace Materials & Structures, Computational Fluid Dynamics, Nano-technology & Robotics. After graduating, he has been working as a freelance Aerospace Engineering consultant. He developed an interest in technical writing during sophomore year of his B.S degree and has wrote several research articles in different publications. During his free time, he enjoys writing poetry, watching movies and playing Football.

Citations

Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Ahmed, Hussain. (2022, September 23). Impact of Chromium and Molybdenum Content On Cobalt-Based Alloys. AZoNano. Retrieved on December 09, 2022 from https://www.azonano.com/news.aspx?newsID=39717.

  • MLA

    Ahmed, Hussain. "Impact of Chromium and Molybdenum Content On Cobalt-Based Alloys". AZoNano. 09 December 2022. <https://www.azonano.com/news.aspx?newsID=39717>.

  • Chicago

    Ahmed, Hussain. "Impact of Chromium and Molybdenum Content On Cobalt-Based Alloys". AZoNano. https://www.azonano.com/news.aspx?newsID=39717. (accessed December 09, 2022).

  • Harvard

    Ahmed, Hussain. 2022. Impact of Chromium and Molybdenum Content On Cobalt-Based Alloys. AZoNano, viewed 09 December 2022, https://www.azonano.com/news.aspx?newsID=39717.

Tell Us What You Think

Do you have a review, update or anything you would like to add to this news story?

Leave your feedback
Your comment type
Submit