The Study Of Preparation, Microstructure And Properties Of Cu-MoS₂ Composites

In this paper, Cu-MoS₂ composites were prepared by powder metallurgy route in hydrogen and argon atmosphere, respectively. The phases, microstructures, mechanical properties and worn surface morphologies of composites were detected by XRD (X-ray diffraction), XPS (X-ray photoelectron spectroscopy), SEM (scanning electron microscope) and EDS (energy dispersion spectrometer) to study the influences of MoS₂ addition and sintering temperature on sintering process and properties of composites. The wear behaviors and mechanisms of composites under room temperature and in atmosphere were investigated in detail. The results can be concluded as follows.During sintering process in H₂ atmosphere, MoS₂ only reacts with Cu into an intricate compound made of Cu, Mo and S elements, with simultaneous emission of copper sulfide and elementary Mo in two steps, rather than with H2. Sintered products vary regularly with the increasing amount of MoS₂ addition. The conclusion of thermodynamics analysis is identical with the results of XRD and XPS. Phases of the composites scatter evenly. With the increase of MoS₂ content, the proportion of matrix phase decreases steadily; the intricate compound increases; and the Mo element disperses among them. The density of the composites gradually decreases; the hardness firstly increases and then declines, finally rises a bit; the bending strength decreases obviously while the resistivity presents an adverse tendency.During sintering process in Ar atmosphere, Cu1.83Mo3S4 is generated due to the reaction of Cu and MoS₂. As the sintering temperature increases, the hardness and the bending strength of composites increase obviously as a result of fuller diffusion and stronger combination between atoms. The resistivity of composites declines at first and then ascends, finally tends to a steady level while reaching the minimum value at the temperature of 750℃.The friction and wear properties of Cu-G(4.5ωt%)-MoS₂(4.5ωt%) composite are the best under the coulomb friction of room temperature because that a continuous solid lubricating film can be formed on friction surface by the lubrication action of G, working in coordination with copper sulfide. The lubricating and antifriction effects of Cu-G(9ωt%) composite are unsatisfactory for the solid lubricating film is not integrated. The wear of Cu-MoS₂(9ωt%) composite is quite serious, the main form of which is adhesion and abrasion, accompanied with oxidation wear.During the coulomb friction in Ar atmosphere, Cu-MoS₂(9ωt%) composite presents the best antifriction and wear properties, while Cu-G(4.5ωt%)-MoS₂ (4.5ωt%) composite takes the second place. The cracking, peeling off and repairing process of solid lubricating film in Cu-MoS₂(9ωt%) composite is dynamical equilibrium; the hardness and strength of the matrix are large enough to sustain the formation of intact solid lubricating film; moreover, the good chemical affinity between copper sulfide and the matrix makes solid lubricating film stick on the matrix much better and stronger. Local areas of Cu-G(4.5ωt%)-MoS₂(4.5ωt%) composite can not be well lubricated as the MoS₂ addition is not sufficient. The G loses its self-lubrication function in Ar atmosphere, which results in bad friction and wear properties of Cu-G(9ωt%) composite.