Abstract
Microstructure Grains Dislocations Friction Wear Lubrication.
Evolution of deformation microstructure and nanohardness of Ag and Ni after friction in the BL regime was studied. All friction tests were conducted under lubricated conditions using a pin-on-disk rig. Pure fee metals such as Ag and Ni, with different SFE (16 and 125 mJm(-2), respectively), were chosen as pin materials. Cross sectional transmission electron microscopy (TEM) lamellae were prepared from the pins using a focused ion beam (FIB). Using TEM, we analysed the regions of the pins that are in steady state after friction; the friction coefficient (mu) and hardness (H-s) remained unchanged with deformation in the BL regime. After the wear tests, the specimens were cross-sectioned in longitudinal and transverse directions (parallel and perpendicular to the direction of friction). Nanoindentations were performed using a Berkovich diamond tip. A gradient of grain sizes during the friction of Ag and Ni in BL regime was revealed by TEM imaging. Deformation twinning followed by limited recovery within the surface of Ag led to the formation of a relatively thick top layer of ultra-fine equiaxial grains. Thermally activated processes for the rearrangement and annihilation of dislocations are accelerated during the friction of Ni due to high SFE and contact temperature. Cross-sectional microstructures observed normal and parallel to the direction of friction are dissimilar. Steady state values of grain size, d(s), and hardness, H-s, after friction in lubricated conditions are explained by the balance between hardening and dynamic recovery in surface layers, and they strongly depend on the SFE and temperature. A correlation between the wear properties (wear coefficient) and total work of deformation during nanoindentation shows a similarity in the nano- and microscales in lubricated friction.
| Original language | English |
|---|---|
| Pages (from-to) | 62-70 |
| Number of pages | 9 |
| Journal | Wear |
| Volume | 404 |
| DOIs | |
| Publication status | Published - 15 Jun 2018 |
Funding
We acknowledge with thanks support from the G. M. J. Schmidt Minerva Center for Supramolecular Architectures. R. T. gratefully acknowledges the support of ERC project INTIF 226639, the Israel Science Foundation, the Harold Perlman Foundation, and the Irving and Cherna Moskowitz Center for Nano and Bio-Nano Imaging. R. T. is the Drake Family Chair of Nanotechnology and Director of the Helen and Martin Kimmel Center for Nanoscale Science.