Tribological Properties Of Cu/NbSe₂ Self-lubricating Composites

Copper-based composites are widely used in transportation,electronics,aerospace and other fields of engineering,which is suitable for making electrical contact materials.The addition of layered solid lubricants such as graphite and MoS₂to copper matrix significantly improves the antifriction and antiwear properties of composites.Copper-based self-lubricating composites need to work in the harsh environment of high vacuum,high load and other special conditions.Graphite does not have significant antifriction properties in the environment of dry and low vacuum.MoS₂ has a higher resistivity and poor conductivity.When a large current is loaded to carry out relative motion,it will generate sparks and cause local high-temperature transients and increase wear.NbSe₂ possesses a layered structure similar to that of graphite and MoS₂.The resistivity of NbSe₂ is 10^-4?.cm,which is much lower than that of graphite(10^-3?.cm)and MoS₂?10²?.cm?.It is a new material with both lubricity and conductivity.Copper-based self-lubricating composites prepared by adding NbSe₂ are expected to become new materials with good conductivity and tribological properties.In this paper,NbSe₂ micro-nanoparticles prepared by pressureless synthesis method are used as lubrication components.Copper-based composites with reinforcing-phases or Enhancing the interface combination between NbSe₂ and matrix are prepared by using the powder metallurgy high temperature sintering method.The UMT-2 wear tester is used to investigate the friction-reducing and wear-resistance properties of copper-based composites.The wear scar is characterized by scanning electron microscope equipped with EDS,Raman spectrometer,and photoelectron spectrometer.The micro-morphology and composition of the copper-based composites are in detail studied in the anti-friction and anti-wear mechanism.The obtained results are divided into the following four aspects:?1?NbSe₂ is synthesized by thermal solid-state reaction.Results show that NbSe₂micro-nano particles with high purity and crystallinity can be prepared by the reaction of Nb and Se at the reaction temperature of 800?for 1h.Copper powder is mixed with a certain amount of NbSe₂ and pressed and sintered to prepare copper-based self-lubricating composites with different NbSe₂ content.The results of friction and wear tests show that as NbSe₂ was added,the friction coefficient and wear rate of copper-based composites firstly decreased and then increased.When the content of NbSe₂ was added to 20wt.%,the friction coefficient and wear rate are 0.13 and5.8×10^-4mm³.N^-1m^-1,respectively.Composites under this composition exhibite the excellent antifriction and antiwear properties..?2?TiB₂ and NbSe₂ are added to copper matrix at a certain ratio,and Cu/TiB₂/NbSe₂ composites are prepared by powder metallurgy.Results show that compared with the addition of NbSe₂,copper-based composites containing NbSe₂ and TiB₂ show better friction-reducing and antiwear properties,especially with the addition of 10wt.%TiB₂ and 10wt.%NbSe₂,the friction coefficient and wear rate are reduced to the lowest value of 0.14 and 2.1×10^-5mm³.N^-1m^-1,respectively,indicating that copper-based composites under the distribution ratio possess the best tribological properties.?3?Cu/RGO/NbSe₂ composites are prepared by using two-dimensional material RGO as reinforcement phase.The experimental results show that as a small amount of RGO is added,the friction coefficient and wear rate of composites decrease obviously.As 2wt.%RGO and 18wt.%NbSe₂ are added,friction coefficient and wear rate are0.08 and 7×10^-5mm³.N^-1m^-1,respectively.However,when the amount of RGO exceeds 2wt.%,NbSe₂ is less than 18wt.%,tribological properties of composites are deteriorated,which is due to the agglomeration of excess RGO.?4?The interface combination seriously affects the performance of composites.NbSe₂ is uniformly coated by Ag by an oxidation-reduction method.Cu/Ag/NbSe₂composites are prepared by adding Ag/NbSe₂ as a lubricating phase to copper matrix.Results show that the silver-plated layer on the surface of NbSe₂ significantly improves the interfacial bonding between NbSe₂ and matrix and the dispersion effect in the matrix.Wear tests show that Ag/NbSe₂ not only inhibits the formation of metal oxides so that reduce oxidation wear,but also exhibits better antifriction and antiwear properties compared to NbSe₂ during the sliding tests.