Effect of SiC particulate reinforcement on the dry sliding wear of aluminium-silicon alloys (A356)

The acting wear mechanisms on metal-on-metal hip joint bearings: in-vitro results

To control and minimize wear of metal-on-metal hip joints it is essential to understand the mechanisms of debris generation. In vivo, mainly nanosize globular and needle-shaped particles are found. These can neither stem from the action of abrasion nor from tribochemical reactions. In this study the acting wear mechanisms have been first identified on the surface by means of scanning electron microscopy (SEM). Afterwards, the microstructures of the subsurface regions of explants have been investigated using a transmission electron microscope (TEM). Observation of the subsurface gave additional insight about the microstructural changes of cobalt-base alloys subjected to wear. At some distance from the surface, a network of stacking faults and hexagonal ϵ-martensite was found strengthening the bulk material. This microstructure changed into a nanocrystalline type moving closer towards the surface. A comparison of in vivo debris size and grain size of the surface suggests that the globular wear particles result from torn off nanocrystals, while the needle shaped particles are generated by fractured ϵ-martensite. Identified cracks, propagating through the nanocrystalline layer, further support these findings. Thus, it is suggested that the dominating mechanism of particle generation for metal-on-metal joints is surface fatigue within a nanocrystalline surface layer. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 72B: 206–214, 2005

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/jbm.b.30132

Subsurface microstructure of metal‐on‐metal hip joints and its relationship to wear particle generation

The pathways of dynamic recrystallization in all-metal hip joints

The evolution of tribolayers during high temperature sliding wear

The mechanism of wear-particle formation during unlubricated sliding wear of several carbon and alloy steels has been investigated by scanning (SEM) and transmission electron microscopy (TEM). Individual debris particles are plate-like and typically 200 to 400 nm in thickness. The thinner particles are generally iron oxides except at low temperatures or in inert atmospheres when predominantly metallic particles result. The mean debris-particle width was 1 to 2 ..mu..m. TEM revealed a fine dislocation cell structure typical of large strain deformation to a depth of 10 to 50 ..mu..m. The subsurface cell dimensions and bending of pearlite colonies indicate that the shear strain near to the surface is at least 5. In many instances, a 200 to 300 nm wide zone of lower dislocation density, indicative of recovery, we noted immediately below the surface. Some cracks formed along dislocation cell walls at the boundary of the recovered zone; others were associated with decohesion of particle interfaces of subgrain triple points. Some oxidation then occurs during separation of the platelet from the parent material as a consequence of the highly pyrophoric nature of thin metal flakes. The sequence of the dry sliding wear process is discussed. 16 figures.

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W.F. Salesky

Papers

Nature and origin of sliding-wear debris from steels