In this project, Argonne National Laboratory (Argonne) and John Crane Inc. will jointly develop an industrial-scale process for forming superlubric coatings based on a graphene-nanodiamond solution. This process will be applied to the dry gas seals of gas compressors and similar equipment, thereby reducing friction in the seals and reducing the leakage of toxic and greenhouse gases through worn seals. By improving the reliability of sealing systems, there is considerable opportunity to reduce emission associated with seal failures, to reduce maintenance costs, and to improve productivity.

Argonne National Laboratory, Lemont, IL 60439
John Crane Inc, Morton Grove, IL 60053

Minimizing friction and wear-related mechanical failures remains one of the greatest challenges in contemporary mechanical systems; the search for new materials, coatings, and lubricants that can reduce such failures continues worldwide. Mechanical shaft seals used in pumps, turbines and centrifugal compressors are critically important components of these systems, which are used in many industries, from paper, pulp, and chemicals to petroleum, oil exploration, and power generating plants. These shaft seals prevent leakage of products from rotating equipment. In many instances the concerned products are toxic gases or hazardous chemicals. The Environment Protection Agency (EPA) has estimated that industrial pumps contribute 12% of total hazardous emissions to the atmosphere. Per the 2014 annual inventory of United States Green House Gas Emissions and Sinks (GHG Inventory), methane emissions reported from compressors for the natural gas production segment was 86,259 metric tons (MT) and for gas process segment was 724,295 MT, and for transmission and storage segment was 1,261,080 MT, for a total of 2,071,633 MT of methane released into the atmosphere.

One method of reducing these leaks is to make seals that is coated with diamond and graphene material that exhibits superlubricity. Superlubricity is the state in which the friction between two sliding surfaces is reduced to nearly zero (coefficient of friction, CoF < 0.005). Superlubricity is highly desirable in order to minimize friction in real-world engineering applications. In a major breakthrough the Argonne team demonstrated for the first time that superlubricity can be achieved at true macroscale in a dry environment by the addition of nanodiamonds and graphene flakes between two surfaces, one made of silicon and one made of diamond-like carbon. In this system, the coefficient of friction was just 0.004, significantly reducing friction losses. The tribological conditions, such as contact pressure, environment, velocity and tribo-pair, used in these tribological tests are compatible with required conditions for John Crane’s gas seal applications; it is therefore appropriate to further develop Argonne’s technology for John Crane’s gas seal applications.

The benefits of graphene coating make an excellent value proposition for John Crane clients in all industries. Project team estimate that this technology, once fully developed and qualified, can be successfully commercialized in 1-2 years. John Crane’s position as a market leader known for its technology developments could successfully introduce graphene coatings into the market based on the company’s extensive manufacturing, distribution, qualification capabilities, and customer base. In addition to the key critical advantages mentioned above, the proposed technology can offer the following benefits consistent with DOE’s ongoing efforts:

1. Energy efficiency: This technology once fully implement will improve the performance of the dry gas seals by enabling lower friction and wear and lower maintenance costs, thereby improving the overall performance of the unit.
2. Reduced costs: Mean time between failures (MTBF) or the time between maintenance schedules for dry gas seals using this technology is expected to increase, thereby reducing the overall cost.
3. Environmental benefits: Improving the operation of the seal will reduce leakage of greenhouse gases into the atmosphere.

• First kick-off meeting including all team members and program managers from DOE  happened via video conference in February 22, 2017
• Initial characterization of the silicon carbide (SiC) substrates (provided by John Crane) including surface topography, composition analysis was completed by Argonne team in May 2017 
• A detailed test matrix was developed by Argonne for Phase I of the project. Initial tests were conducted at different loads and speeds at Argonne to understand the performance of the base materials supplied by John Crane. 
• All the initial data was presented and discussed with John Crane team. Both teams have very good understanding of the test parameters to be used and any other improvements that could be done to replicate the test conditions used by John Crane for Pin-on-disc testing.
• John Crane provided the test requirements of material pairs and qualification criteria in June 2017 and Argonne team completed the experimental design and estimated samples required to conduct the experiments. 
• Based on the criteria specified by John Crane, DLC coated parts from John Crane’s supplier and Argonne DLC coated parts were tested at Argonne with four (4) different solid lubricants that were developed at Argonne and results were discussed with John Crane.  
• John Crane conducted pin-on-disc (POD) tribometer studies at their facility to further determine the best tribo-pair and solid lubricant combination to be considered for Phase II work of this project. 
• After finishing the tribo-testing by John Crane, the data was shared with Argonne in December 2017. It was realized that most of the tribological tests carried out in the dry nitrogen atmosphere at John Crane facility were not matching with that of carried out at Argonne.
• All the samples tested at John Crane facility were returned to Argonne for further characterization and detailed post characterization of all the samples were conducted at Argonne in January 2018.
• It was concluded that the DLC coating provided by one of the vendor of John Crane for the second batch was different including some variation in the base substrates morphology and that was the main reason for inconsistency in the PoD tests carried out at Argonne and John Crane. 
• PoD validation tests were conducted at Argonne by using new DLC Discs coated by John Crane’s supplier with all four different solid lubricants under dry Nitrogen conditions at specified load and speed conditions. The test results were in agreement with previous benchmarks.
• Argonne-John Crane analyzed the test data and selected 3 out of 4 solid lubricants that showed improved performance and confirmed to proceed to the next phase i.e. Disc on Disc (DoD) tests in May 2018, which is Phase-II part of the project 
• DoD parts were received by Argonne in August 2018 for initial characterization. Argonne developed the solid lubricant application procedure and shared that with John Crane researchers.
• Solid lubricants (3) were sent to John Crane facility to apply on DoD parts and conduct testing in September 2018. 
   

John Crane tested the performance of various solid lubricants developed for the DoD tests and down-selected one solid lubricant, which performed well in both dry nitrogen and air atmospheres. More optimization of the solid lubricant is necessary to extend its performance life and is underway. Argonne characterized the tested DoD parts received form John Crane in December 2018. Based on the analysis:

• Argonne modified the formulation of the promising solid lubricant to make it last for extended time period. 
• New version of solid lubricant will be shipped to John Crane facility for further testing and evaluation in Jan 2019
• John Crane will proceed to next phase(part of Phase-III) test i.e. limited time slow-roll rig test using solid lubricant in Jan 2019/Feb 2019

$579,992.00

$579,992.00

NETL – Joseph Renk (joseph.renk@netl.doe.gov or 412-386-6406)

Argonne National Laboratory – Anirudha V. Sumant (sumant@anl.gov or 630-252-4854)

John Crane Inc. – Jorge Pacheco (Jorge.Pacheco@johncrane.com or (847) 967-3744)