High temperature tribological behaviour of carbon based (B 4C and DLC) coatings in sliding contact with aluminum

Carbon based coatings, particularly diamond-like carbon (DLC) films are known to resist aluminum adhesion and reduce friction at room temperature. This attractive tribological behaviour is useful for applications such as tool coatings used for aluminum forming and machining. However, for those opera...

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Bibliographic Details
Published in:Thin solid films 2010-12, Vol.519 (5), p.1611-1617
Main Authors: Gharam, A. Abou, Lukitsch, M.J., Balogh, M.P., Alpas, A.T.
Format: Article
Language:English
Subjects:
Alloys
Aluminum
Aluminum adhesion
Aluminum base alloys
Boron carbide
Carbon
Coating fracture
Coatings
Condensed matter: structure, mechanical and thermal properties
Cross-disciplinary physics: materials science
rheology
Diamond-like carbon films
DLC
Exact sciences and technology
Friction
Fullerenes and related materials
diamonds, graphite
High temperature sliding
Materials science
Mechanical and acoustical properties
Physical properties of thin films, nonelectronic
Physics
Specific materials
Structure and morphology
thickness
Surfaces and interfaces
thin films and whiskers (structure and nonelectronic properties)
Thin film structure and morphology
Tribology
Wear
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Summary:Carbon based coatings, particularly diamond-like carbon (DLC) films are known to resist aluminum adhesion and reduce friction at room temperature. This attractive tribological behaviour is useful for applications such as tool coatings used for aluminum forming and machining. However, for those operations that are performed at elevated temperatures (e.g. hot forming) or that generate frictional heat during contact (e.g. dry machining) the suitable coatings are required to maintain their tribological properties at high temperatures. Candidates for these demanding applications include boron carbide (B 4C) and DLC coatings. An understanding of the mechanisms of friction, wear and adhesion of carbon based coatings against aluminum alloys at high temperatures will help in designing coatings with improved high temperature tribological properties. With this goal in mind, this study focused on B 4C and a hydrogenated DLC coatings sliding against a 319 grade cast aluminum alloy by performing pin-on-disk experiments at temperatures up to 400 °C. Experimental results have shown that the 319 Al/B 4C tribosystem generated coefficient of friction (COF) values ranging between 0.42 and 0.65, in this temperature range. However, increased amounts of aluminum adhesion were detected in the B 4C wear tracks at elevated temperatures. Focused ion beam (FIB) milled cross sections of the wear tracks revealed that the coating failed due to shearing along the columnar grain boundaries of the coating. The 319 Al/DLC tribosystem maintained a low COF (0.15–0.06) from room temperature up to 200 °C. This was followed by an abrupt increase to 0.6 at 400 °C. The deterioration of friction behaviour at T > 200 °C was attributed to the exhaustion of hydrogen and hydroxyl passivants on the carbon transfer layer formed on the Al pin.
ISSN:0040-6090
1879-2731
DOI:10.1016/j.tsf.2010.07.074