August 7, 2017

New solid lubricant shown to reduce friction and wear on steel surfaces

graphical abstract This composite image depicts the makeup and performance of a new non-liquid lubricant developed by researchers at Purdue University. (Purdue University image/ Abdullah A. Alazemi) Download image

WEST LAFAYETTE, Ind. – Researchers have created a new type of non-liquid lubricant that has been shown to reduce friction and wear significantly under the extreme conditions found in various applications, from air compressors to missile systems.

The new liquid-free composite is made from a slurry of a material called graphene, zinc oxide, and the polymer polyvinylidene difluoride. Graphene is an extremely thin layer of carbon that has many potential technological applications, including lubrication.

“It has superior thermal conductivity, high strength and provides ultralow friction,” said Vilas Pol, an associate professor of chemical engineering at Purdue University.

The nanosize zinc-oxide particles the team developed allow the lubricant to stick to the metal surface, and the polymer binds the whole mixture together, said chemical engineering graduate student Arthur Dysart.

Solid lubricants are needed for applications such as air compressors, equipment used in the food industry, space vehicles, gear-and-chain mechanisms, fasteners found in high-temperature environments, missile systems, high-speed printers, hydraulic motors in winches, cranes and military vehicles, high-performance shredders and drilling rigs.

“The fundamental causes of mechanical failure are friction and wear, so reducing these factors improves the performance and lifetime of many mechanical systems,” said Farshid Sadeghi, Purdue’s Cummins Distinguished Professor of Mechanical Engineering. “Despite recent advances, liquid lubricants cannot be used in situations of high temperature or low pressure such as a vacuum environment, so dry solid-state lubricants are a viable alternative to their liquid counterparts in extreme operating environments.” 

zinc graphic This image, taken using a scanning electron microscope and energy-dispersive x-ray spectroscopy, shows zinc particles within a new type of non-liquid lubricant developed by researchers at Purdue University. (Purdue University image/Arthur Dysart) Download image

Researchers tested stainless-steel surfaces coated with the new lubricant.

“We tested it under worst-case scenarios,” said mechanical engineering graduate student Abdullah A. Alazemi.

Findings were detailed in a research paper published on July 11 in the in the journal Carbon.

“The durability and resilience of this adhesive coating suggest exceptional potential as a dry lubricant for high load-bearing applications,” Pol said.

The researchers found that the composite lubricant sets up a film that significantly improves friction and wear reduction. Raman spectroscopic analysis of wear scars revealed this persistent protective film on contact surfaces.

A complete list of the paper’s co-authors is available in the abstract.

The research is ongoing, and future work is planned with industrial partners. The researchers applied for a patent through the Purdue Research Foundation’s Office of Technology Commercialization. 

Writer: Emil Venere, 765-494-4709, venere@purdue.edu 

 Sources: Vilas G. Pol, 765-494-0044, vpol@purdue.edu

Farshid Sadeghi, 765-494-5719, sadeghi@purdue.edu 

Note to Journalists: The research paper is available from Emil Venere, 765-494-4709, venere@purdue.edu


ABSTRACT

Novel tertiary dry solid lubricant on steel surfaces reduces significant friction and wear under high load conditions  

Abdullah A. Alazemi a, 1, Arthur D. Dysart b, 1, Steven J. Shaffer c, Vilas G. Pol b, *, Lars-Erik Stacke d, Farshid Sadeghi a, **

aSchool of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907, United States, bDavidson School of Chemical Engineering, Purdue University, cBruker Nano Surfaces Division, San Jose, Calif., dSKF Digital Business Technology, Göteborg, Sweden

*Corresponding authors: vpol@purdue.edu, sadeghi@purdue.edu,  

A novel graphene-zinc oxide composite film is created and studied as a solid-state lubricant for friction and wear reduction under extreme load conditions. The liquid-free composite is made from a slurry of graphene, zinc oxide, and polyvinylidene difluoride spin-coated onto a stainless steel substrate. Enhanced tribological performance was measured under ambient conditions using a ball-on-disk tribometer with contact pressures up to 1.02 GPa and sliding distances up to 450 m. The graphene-rich lubricant demonstrates substantial friction and wear reduction (ca. 90%) compared to unlubricated sliding. The composite film is able to maintain its lubricating effects under extreme operating conditions including 15 N normal load and 450 m sliding distance. Following tribological testing, optical and spectroscopic analysis of the formed wear scars reveal a persistent protective film on the ball and disk surfaces. The excellent tribological performance of this graphene-rich composite is attributed to the adhesion effect from zinc oxide: zinc adheres graphene to the contact interface, maintaining improved tribological performance under high contact pressure. The durability and resilience of this adhesive coating suggest exceptional potential as a dry lubricant for high load-bearing applications.


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