Friction and Wear Mechanisms of Tungsten–Carbon Systems: A Comparison of Dry and Lubricated Conditions

Abstract

The unfolding of a sheared mechanically mixed third-body (TB) in tungsten/tungsten carbide sliding systems is studied using a combination of experiments and simulations. Experimentally, the topographical evolution and the friction response, for both dry and lubricated sliding, are investigated using an online tribometer. Ex situ X-ray photoelectron spectroscopy, transmission electron microscopy, and cross-sectional focused ion beam analysis of the structural and chemical changes near the surfaces show that dry sliding of tungsten against tungsten carbide results in plastic deformation of the tungsten surface, leading to grain refinement, and the formation of a mechanically mixed layer on the WC counterface. Sliding with hexadecane as a lubricant results in a less pronounced third-body formation due to much lower dissipated frictional power. Molecular dynamics simulations of the sliding couples predict chemical changes near the surface in agreement with the interfacial processes observed experimentally. Finally, online topography measurements demonstrate an excellent correlation between the evolution of the roughness and the frictional resistance during sliding.

Surface Softening in Metal–Ceramic Sliding Contacts: An Experimental and Numerical Investigation

“…In parallel, the tungsten carbide counter face forms a mechanically mixed amorphous layer within the contact area, as revealed by TEM images. 10 While the existence of these third bodies is already known, here the aim is to provide a better understanding of the chemical evolution leading to the variation in microstructure.…”

“…These observations are consistent with previous analysis of WC/W tribo couples by means of TEM. 10 A lateral resolved 3D tomographical XPS chemical analysis within the contact area of the tungsten carbide and the tungsten specimen (Figures 3À5) is performed in order to provide a better understanding on the lateral distribution of the different binding states. Figures 3À5 show atomic concentration maps of oxygen bound as tungsten oxide, carbon bound as tungsten carbide, and tungsten bound as metallic tungsten, respectively.…”

Dependence of tribofilm characteristics on the running-in behavior of aluminum–silicon alloys

“…To elucidate on these variations of the tribological response, we investigated the third bodies in terms of their elemental composition, structure, and mechanical behavior. The worn surfaces for both the low and high contact pressures showed an increase in the oxide content compared to the unworn surface, which is quite common in metallic sliding contacts [20][21][22][23][24], in particular for aluminum alloys [1,4,13,25,26]. In addition, the cross-sectional SEM images revealed a grain refinement in the near-surface region, which is thicker for the sliding tests performed at a lower contact pressure (i.e., 15 MPa) compared to the higher one (i.e., 35 MPa).…”

Numerical Investigation of Third‐Body Behavior in Dry and Wet Environments under Plane Shearing

“…For dry contacts, e.g., for tungsten/tungstencarbide-contact pairs, material transfer was detected in a nanoscopic range. This does not occur in lubricated systems, resulting in a significantly lower force required for the relative movement of the contact partners [12]. These results were also confirmed for pairings of tungsten and diamond-like carbon [11].…”

“…The emergence and behavior of tribomaterials in simplified systems has already been described with molecular dynamic simulations (MD) and was verified in experiments [1,11,12]. The MD simulations are capable of showing the different behavior of dry and lubricated contacts on small spatial and temporal scales.…”