Subsurface characterisation of wear on mechanically polished and electro-polished biomedical grade CoCrMo
Subsurface characterisation of wear on mechanically polished and electro-polished biomedical grade CoCrMo
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DOI：
10.1016/j.wear.2015.02.007
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发表时间：
2015-05
期刊：
影响因子：
5
通讯作者：
P. Zeng;A. Rana;R. Thompson;W. M. Rainforth
中科院分区：
文献类型：
--
作者：
P. Zeng;A. Rana;R. Thompson;W. M. Rainforth
钴铬钼合金已广泛用于金属对金属全髋关节置换术（THR）。然而，由于身体对磨损碎屑和腐蚀产物的反应导致的不良局部组织反应，金属对金属植入物的使用最近受到严重质疑。了解金属对金属THR的磨损情况，从而降低磨损率和金属离子的溶解是非常重要的。据报道，在体内和体外CoCrMo THR的最高表面上都有纳米晶层，并且被认为在材料的耐磨性中起关键作用。目前的工作提供了一个详细的研究后，往复磨损试验的生物医用钴铬钼表面损伤。通过比较标准机械抛光和电抛光表面，研究了起始表面结构的系统差异。广泛使用的横截面透射电子显微镜（TEM）被施加到评估的纳米晶层的演变。结果表明，在机械抛光后的横截面样品中没有观察到纳米晶层，但有大量的ε-马氏体和机械孪晶形成。相比之下，电抛光表面表现出最小的变形迹象。两个起始表面在滑动接触期间形成纳米晶层，但速度不同。对于机械抛光的表面，纳米晶层远比电抛光的表面更广泛。因此，这表明纳米晶层通过一些高应变剪切过程从先前的ε-马氏体结构形成，并且在纳米晶层开始形成之前，表面中需要最小塑性应变。详细讨论了其形成机理。
CoCrMo alloys have been widely used for metal-on-metal total hip replacements (THRs). However, the use of the metal-on-metal implants has recently been seriously called into question due to adverse local tissue reactions due to the response of the body to wear debris and corrosion products. It is important to understand the wear of metal-on-metal THRs, hence to reduce the wear rate and metal ion dissolution. A nanocrystalline layer has been reported on the topmost surface of bothin vivoandin vitroCoCrMo THRs and is believed to play a key role in the wear resistance of the material. The current work provides a detailed study of surface damage of biomedical CoCrMo after reciprocating wear testing. Systematic differences in the starting surface structure were investigated through a comparison of a standard mechanical polished and an electropolished surface. Extensive use of cross-sectional transmission electron microscopy (TEM) was applied to evaluate the evolution of the nanocrystalline layer. It was found that the nanocrystalline layer was not observed in cross-section samples from the as-mechanically polished surface, however there was extensive formation of ε-martensite and mechanical twins. In contrast, the electro-polished surface exhibited minimal evidence of deformation. The nanocrystalline layer developed during sliding contact for both starting surfaces, but at different rates. For the mechanically polished surface, the nanocrsytalline layer was far more extensive than for the electro-polished surface. Thus, this suggests that the nanocrystalline layer forms through some high strain shear process from the prior ε-martensite structure, and that a minimum plastic strain is required in the surface before the nanocrystalline layer starts to form. The formation mechanisms are discussed in detail.