Graphite lubrication mechanisms under high mechanical load

Morstein, Carina Elisabeth; Dienwiebel, Martin

doi:10.1016/j.wear.2021.203794

Cited by 34 publications

(17 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…2 b). This value is in line with previous experiments 22 , where an increase in friction was observed with a decrease in normal force (e.g., at P Hertz = 250 MPa a μ = 0.29 was measured).…”

Section: Resultssupporting

confidence: 93%

“…For RH ≤ 30%, (Fig. 3 b, c), a thin carbon layer remains in the middle of the wear track, as seen in previous studies on substrates with industrial surface roughness values 22 . For high humidity (45% RH, Fig.…”

Section: Resultssupporting

confidence: 82%

“…In our experiments with high humidity (≥37% RH) the steady-state low friction regime was only short-lived and followed by an abrupt rise in friction. This observation is accompanied by extensive material transport of the graphite coating out of the wear track, resulting in a breakdown of solid lubrication and CoF values that are comparable to those of bare steel-steel contacts as shown by previous studies 22 . This trend is also visible in the wear behavior in Fig.…”

Section: Discussionsupporting

confidence: 68%

See 2 more Smart Citations

Humidity-dependent lubrication of highly loaded contacts by graphite and a structural transition to turbostratic carbon

et al. 2022

Self Cite

View full text Add to dashboard Cite

Graphite represents a promising material for solid lubrication of highly loaded tribological contacts under extreme environmental conditions. At low loads, graphite’s lubricity depends on humidity. The adsorption model explains this by molecular water films on graphite leading to defect passivation and easy sliding of counter bodies. To explore the humidity dependence and validate the adsorption model for high loads, a commercial graphite solid lubricant is studied using microtribometry. Even at 1 GPa contact pressure, a high and low friction regime is observed - depending on humidity. Transmission electron microscopy reveals transformation of the polycrystalline graphite lubricant into turbostratic carbon after high and even after low load (50 MPa) sliding. Quantum molecular dynamics simulations relate high friction and wear to cold welding and shear-induced formation of turbostratic carbon, while low friction originates in molecular water films on surfaces. In this work, a generalized adsorption model including turbostratic carbon formation is suggested.

show abstract

Section: Resultssupporting

confidence: 93%

Section: Resultssupporting

confidence: 82%

Section: Discussionsupporting

confidence: 68%

See 1 more Smart Citation

Humidity-dependent lubrication of highly loaded contacts by graphite and a structural transition to turbostratic carbon

et al. 2022

Self Cite

View full text Add to dashboard Cite

show abstract

“…Surface four from a graphite-coated plate was used for micro tribological sliding tests (Figure 3). This specimen origins from an investigation of the graphite friction behavior [24] and shows the structure of a coated surface. The brake disc was made from cast iron.…”

Section: Probe Preparationmentioning

confidence: 99%

An Approach for the Transfer of Real Surfaces in Finite Element Simulations

et al. 2021

View full text Add to dashboard Cite

Virtual simulations are a relevant element in product engineering processes and facilitate engineers to test different concepts during early phases of the development. However, in tribological product engineering, simulations are hardly used because input data such as material behavior are often missing. Besides the material behavior, the surface roughness of the contacting elements is relevant for tribological systems. To expand the capabilities of the virtual engineering of tribological components such as bearings or brakes, the hereby presented approach allows for the depiction of real rough surfaces in finite element simulations. Rough surfaces are scanned by a white-light interferometer (WLI) and further processed by removing the outliers and replacing non-measured samples. Next, a spline generation creates a solid body, which is imported to CAD software and afterwards meshed with triangle and quadrilateral elements in different sizes. The results comprise the evaluation of six differently manufactured (turned, coated, and pressed) real surfaces. The surfaces are compared by the deviations of the roughness values after measuring with the WLI and after meshing them. Furthermore, the elements’ aspect ratios and skewness describe the mesh quality. The results show that the transfer is dependent upon deep cliffs and large Sz values in comparison to the lateral expansion.

show abstract

“…Crystallizers in the continuous casting process, especially copper and its alloys, and at much lower rate precious metals and their alloys, are usually made of graphite-based materials. One of their most important features is the fact that these graphite materials are hardly wettable by copper and, moreover, have high thermal conductivity and self-lubrication properties [ 24 , 25 , 26 , 27 , 28 ]. A different group of crystallizers are solutions used in continuous casting systems appropriated for steel.…”

Section: Introductionmentioning

confidence: 99%

External Surface Quality of the Graphite Crystallizer as a Factor Influencing the Temperature of the Continuous Casting Process of ETP Grade Copper

et al. 2021

View full text Add to dashboard Cite

Today’s world is a place where lack of electrical energy would be unimaginable for most of society. All the conductors in the world, both aluminum and copper, have their origin in various types of casting lines where the liquid metal after crystallization is being processed into the form of wires and microwires. However, the efficiency of the continuous casting processes of metals and the final quality of the manufactured product strictly depend on the design of the used crystallizers, the materials used during its production and its quality. Research conducted in this paper focuses on the latter, i.e., external surface quality of the graphite crystallizer at the place of contact with the primary cooling system. In order to quantify its influence on the continuous casting process numerical analyses using the finite element method has been conducted, which results have been further confirmed during empirical tests in laboratory conditions. It has been proven with all of the proposed methods that the temperature of the obtained cast rod is closely linked to the aforementioned surface quality, as when its roughness coefficient surpasses a certain value the temperature of the obtained product increases almost twofold from approx. 150–170 °C to 300–320 °C. These values might influence the quality and final properties of the cast rod, the susceptibility to wire drawing process and possible formation of wire drawing defects and therefore be of much importance to the casting and processing industry.

show abstract

Graphite lubrication mechanisms under high mechanical load

Cited by 34 publications

References 32 publications

Humidity-dependent lubrication of highly loaded contacts by graphite and a structural transition to turbostratic carbon

Humidity-dependent lubrication of highly loaded contacts by graphite and a structural transition to turbostratic carbon

An Approach for the Transfer of Real Surfaces in Finite Element Simulations

External Surface Quality of the Graphite Crystallizer as a Factor Influencing the Temperature of the Continuous Casting Process of ETP Grade Copper

Contact Info

Product

Resources

About