Indentation Hardness Measurements at Macro-, Micro-, and Nanoscale: A Critical Overview

The Brinell, Vickers, Meyer, Rockwell, Shore, IHRD, Knoop, Buchholz, and nanoindentation methods used to measure the indentation hardness of materials at different scales are compared, and main issues and misconceptions in the understanding of these methods are comprehensively reviewed and discussed. Basic equations and parameters employed to calculate hardness are clearly explained, and the different international standards for each method are summarized. The limits for each scale are explored, and the different forms to calculate hardness in each method are compared and established. The influence of elasticity and plasticity of the material in each measurement method is reviewed, and the impact of the surface deformation around the indenter on hardness values is examined. The difficulties for practical conversions of hardness values measured by different methods are explained. Finally, main issues in the hardness interpretation at different scales are carefully discussed, like the influence of grain size in polycrystalline materials, indentation size effects at micro-and nanoscale, and the effect of the substrate when calculating thin films hardness. The paper improves the understanding of what hardness means and what hardness measurements imply at different scales.Funding Agencies|Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University ((Faculty Grant SFO Mat LiU) [2009 00971]</p

Tribocorrosion behavior and ions release of CoCrMo alloy coated with a TiAlVCN/CNx multilayer in simulated body fluid plus bovine serum albumin

While the CoCrMo biomaterial is currently employed in artificial joints, there are medical concerns regarding its metal ion release and material loss caused by tribocorrosion. In this work, a TiAlVCN/CNx multilayer coating has been employed to improve the tribocorrosion-resistance of the CoCrMo substrate. During the tribocorrosion test, with the sample immersed in a simulated body fluid containing bovine serum albumin, open-circuit potential measurements showed more noble potential as well as a reduction of both the friction coefficient and wear-rate during the sliding phase. Inductive coupled plasma results demonstrate that the multilayer coating effectively blocked the emigration of metallic ions.Funding Agencies|CONACYT [FOMIX Jal-2010-10-149472]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; Tecnologico de Monterrey research seed fund</p