Graphene Modified Tungsten Carbide Self-lubricating Wear-resistant Additive

Graphene is a new kind of carbon material, which is closely packed with carbon atoms into a single two-dimensional honeycomb lattice structure. It is the basic unit of building the most commonly used solid lubricant - graphite. It has lower friction coefficient than graphite. It is a new kind of additive for self-lubricating antiwear coating.

Some scholars used the preparation process of graphene modified tungsten carbide self-lubricating wear-resistant additive to obtain the self-lubricating wear-resistant additive with tungsten carbide in situ on the surface of graphene. The preparation process is as follows:

1.A certain amount of graphite powder was added to the solution consisting of concentrated H₂SO₄ (12mL), K2S2O8 (2.5g) and P₂O₅ (2.5g), and the reaction time was 4.5 hours at 80 ~℃. Cool to room temperature and add 0.5 L deionized water. It is dried at room temperature. The pre-oxidized graphite powder was added to 150 mL concentrated H₂SO₄. The temperature was kept at 0 ℃ in ice-water bath, 15 gKMnO₄ was added gradually, and the temperature was not more than 20 after adding, the graphite powder was stirred at 35 ℃ for 2 hours. Then add 250 mL deionized water and stir for 2 hours. Then add 0.7 L deionized water, add 30 mL 30% H₂O₂, dry at room temperature, then dialysis in the dialysis bag for 1 week, remove the impurities. Finally, graphene oxide was obtained by vacuum filtration and drying at room temperature.

2. Weigh 1 g graphene oxide, add 1000g absolute ethanol, mix evenly, add 50 g deionized water to mix. In the ultrasonic disperser, choose 10 mm amplitude bar, ultrasonic treatment time is 30 min, ultrasonic frequency is 10 Hz, obtain the mixture of graphene dispersion, and call the mass percentage of ammonium metatungstate 99%. Mixed with 1% carbonyl tungsten to form tungsten-containing precursor mixture, weighed 1 g tungsten-containing precursor mixture and added to graphene dispersion solution, stirred for 30 minutes, dripped anhydrous ethanol continuously in the stirring process, dripped 18 g, then the precipitation was filtered, heated at 70 ℃ in the oven, dried for 10 minutes, and the dried powder was obtained. A self-lubricating and wear-resistant additive of graphene modified tungsten carbide was obtained by placing a certain amount of H₂ in a crucible of alumina in a tubular reduction furnace with a flow rate of l00sccm, heating to 700 C at a heating rate of 5 ℃/min, holding time of 1 h, and cooling to room temperature through H₂.

Graphene modified coatings were prepared by explosive spraying. The final thickness of the coatings was 0.2 mm after polishing. The test parameters are: wear time 10 min, frequency 30 Hz, displacement amplitude D 2 mm. The average friction coefficient and wear weight loss of tungsten carbide coatings are 0.65 and 3.7 mg respectively. The average friction coefficient and wear weight loss of WC-Co coatings modified by graphene were 0.47 and 2.1 mg respectively. By comparison, the prepared graphene modified self-lubricating and wear-resistant additives have better self-lubricating properties for tungsten carbide coatings. The self-lubricating and wear-resistant additive modified by graphene can reduce the wear and wear of tungsten carbide coating.

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