PurposeThe purpose of this paper is to prepare a novel nano magnetic grease with favorable lubricating performance; to contrast the tribology performance of the magnetic grease with the original grease, and to find the lubricating mechanism of the magnetic grease.Design/methodology/approachThe nano Fe3O4 magnetic fluids are added into the general urea grease to synthesize the nano magnetic grease. Tribology performance tests of the magnetic grease and the original grease are contrasted on a MMW‐1 four‐ball tester. Based on three kinds of effects caused by the nano magnetic fluids, the lubricating mechanism of the magnetic grease is discussed.FindingsNano magnetic grease with favorable lubricating performance can be synthesized by adding the nano Fe3O4 magnetic fluids into the general urea grease. The nano magnetic grease has better lubricating performance and more steady bearing capability than the original grease, and is especially available for the lubricating of equipment with high speed and heavy load. The performance improvement of the magnetic grease is owing to the interactions of three kinds of effects as follows: the viscosity increasing effect, the micro‐rolling effect, and the friction weakening effect, which are all caused by the nano magnetic fluids added into the grease.Originality/valueThe paper documents that the nano Fe3O4 magnetic fluids added into the urea grease to synthesize a novel nano magnetic grease has been proved to have quite favorable lubricating performance by the tribology experiments, and the lubricating mechanism of the magnetic grease is also discussed.

The application of magnetic fluid in ferrography has improved the technique for separating nonferrous wear debris by magnetic means. Brass debris was used as an example to analyze the magnetization mechanism based on ferrographic experiments and molecular analysis. The results show that the nanomagnetic particles in magnetic fluid attach to the surface of the micro nonferrous debris by the functional group of surfactant molecule so as to develop in that debris a positive susceptibility and make it responsive to the magnetic field. The magnetic action of the magnetic particles is selective as to the property of the debris surface to which it attaches, and the magnetization time depends on how readily of the attachment. Mathematical derivation based on mechanical models shown that the magnetic force exerted on the debris is strong enough for its precipitating on ferrogram.

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