Microstructural characterization of low and high carbon CoCrMo alloy nanoparticles produced by mechanical milling

T A Simoes,A E Porter,A E Goode,S J Milne,R M D Brydson,A P Brown,M P Ryan

doi:10.1088/1742-6596/522/1/012059

T A Simoes, A E Porter + Show 5 more

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https://doi.org/10.1088/1742-6596/522/1/012059

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Abstract

CoCrMo alloys are utilised as the main material in hip prostheses. The link between this type of hip prosthesis and chronic pain remains unclear. Studies suggest that wear debris generated in-vivo may be related to post-operative complications such as inflammation. These alloys can contain different amounts of carbon, which improves the mechanical properties of the alloy. However, the formation of carbides could become sites that initiate corrosion, releasing ions and/or particles into the human body. This study analysed the mechanical milling of alloys containing both high and low carbon levels in relevant biological media, as an alternative route to generate wear debris. The results show that low carbon alloys produce significantly more nanoparticles than high carbon alloys. During the milling process, strain induces an fcc to hcp phase transformation. Evidence for cobalt and molybdenum dissolution in the presence of serum was confirmed by ICP-MS and TEM EDX techniques.

Highlights

Hip replacement surgery is one of the most successful medical operations and has been a good treatment for arthritis and other joint diseases in terms of chronic pain[1]
The difference in the absolute degree of dissolution between the high and low carbon powders shown in ICP is likely related to the Ostwald-Freundlich relation, where the particle solubility is inversely proportional to particle size, Transmission Electron Microscopy (TEM) having revealed that the low carbon alloy produced more nanoparticles
Mechanical milling of CoCrMo-C alloy atomized powders has been shown to decrease particle size to between 10-200nm which is comparable with that seen in real wear debris released by hip implants

Summary

Introduction

Hip replacement surgery is one of the most successful medical operations and has been a good treatment for arthritis and other joint diseases in terms of chronic pain[1]. Both high and low carbon CoCrMo alloys are utilised in MoM hip implants. This paper investigates ball milling of low and high carbon CoCrMo alloy gas atomized powders in order to simulate the effects of mechanical wear of the alloy during implant use.

Results

Conclusion