Abstract
Indentation hardness tests were performed on thick, fine-grained, electro-formed deposits of copper and nickel using Knoop, Vickers, and Berkovich indenters. The latter type of indenter was used for shallow penetrations (85-1750nm), and results are reported in terms of nanoscale hardness (NH) numbers. Knoop and Vickers indenters were used with applied loads of between 0.15 and 0.98 N, and at the lowest load, produced indentation depths comparable to the larger ones obtained with the Berkovich indenter. The NH numbers became very sensitive to penetration depth when the penetration depth was less than certain critical values. NH numbers for Cu and Ni were higher than those for Knoop and Vickers testing at comparable penetration depths. Applying indenter area function corrections to calculate hardness numbers (i.e., considering projected area versus facet contact area) resulted in a closer correlation between microhardness and nanohardness scales; however, changes in the tip shape because of wear or other imperfections can lead to inaccurate calculation of NH numbers at the lowest loads. Results also suggest that the interconversion of lowload hardness numbers from one scale to another can be material-dependent.
| Original language | English |
|---|---|
| Pages (from-to) | 287-293 |
| Number of pages | 7 |
| Journal | Materials Characterization |
| Volume | 30 |
| Issue number | 4 |
| DOIs | |
| State | Published - Jun 1993 |
Funding
Microindentation hardness testing has been a valuable tool for materials research, and it is becoming more and more important as component miniaturization and surface engineering fields grow. The necessity to characterize the mechanical properties of very small volumes of material (e.g., in thin films and coatings) has led to an increased interest in low load (for the present purposes, <1.0 N) microindentation tests. When one is using such low loads, second-order effects such as the perfection of the indenter, knowledge of the exact load being applied, low-amplitude external vibrations, elastic impres- sion recovery, and accuracy of impression measurement become much more important. Current microhardness testing guidelines such as ASTM Standard Test Method E 384 \[1\a] re generally inadequate for low-load hardness testing. For example, in many important coated material systems, it may not be possible to limit the indentation depth of conventional Knoop or Vickers indenters to 0.1 times the thickness of the material being tested, and interpretation of the significance of hardness numbers obtained on indented-through surface layers is not straightforward (e.g., \[2, 3\]). In attempting to explore the micromechanical surface properties of such surface treatments as ion im- * Research sponsored by the Office of Transportation Materials, Tribology Program, U.S. Department of Energy, under contract DE-AC05-84OR21400w ith Martin Marietta Energy Systems, Inc. This work, relatedt o scale-effectisn tribology, wasf undedin part by the Departmenotf Energy, Officeo f TransportatioMna terials,T ribologyP ro-gram. The commentosf W. C. Oliver and M. K. Ferber, Oak Ridge National Laboratory,w ere greatlya ppreciateda,s was the technicaal ssis-tanceo fJ. M. Kachidza,g raduates tudenat t the Universityo f Illinois.
| Funders | Funder number |
|---|---|
| Departmenotf Energy, Officeo f TransportatioMna terials | |
| Office of Transportation Materials | |
| U.S. Department of Energy | DE-AC05-84OR21400w |