Fabrication And Tribological Properties Of Ni Matrix High Temperature Self-lubricating Composites

In order to mitigate the the failure of traditional lubricating oil?or fat?under high temperature conditions,and reduce the influence of friction and wear on solid materials over a wide range of temperatures,the high-temperature self-lubricating nickel-alloy-based composites were prepared by the matrix of Ni60 alloy powder with different SrSO₄ content and different LaF₃ content.The mechanism of solid lubricants and the synergistic effect between different lubricants were investigated.The HT-1000 high temperature friction and wear tester was used to test the friction coefficient and wear rate of the composites from room temperature?RT,with 25??to800?in air.The morphologies of the wear scar were analyzed by SEM and XRD.And the effect of the phase compositions and microstructures on the self-lubricating mechanism of nickel-based composites was mainly studied in the wide temperature range.The main research results obtained are as follows:1.Nickel-based high-temperature self-lubricating composites were fabricated by coordinating component matching and optimizing process parameters by cold press forming-vacuum sintering and spark plasma sintering?SPS?.2.With the addition of SrSO₄,the hardness of the nickel-based self-lubricating composite was reduced.With the addition of the rare earth compound LaF₃,the hardness of the composite was improved.3.With the addition of SrSO₄,the friction coefficient of the composites prepared by vacuum sintering increased first and then decreased,and the wear rate decreased.When the content of SrSO₄ was 10 wt%,the composites exhibited the best tribological properties from RT to 800?.The average friction coefficient reached a minimum of0.211 at 600?,and the average wear rate reached a minimum of 4.63×10^-44 mm³/N·m at 400?.With the addition of LaF₃,the coefficient of friction and wear rate of the composites prepared by vacuum sintering remained at a lower level throughout the test temperature range.When the LaF₃ content is 6 wt%,the average friction coefficient reached a minimum of 0.222 at 400?,and the average wear rate reached a minimum of 1.23×10^-44 mm³/N·m at 400?.Due to the appearance and the synergistic effect of La₆MoO₁₂ and SrMoO₄ reduced the wear process,which improved the tribological properties under this condition.4.With the addition of SrSO₄,the tribological properties of the composites sintered by SPS improved in a wide temperature range.When the SrSO₄ content is 10wt%,the average friction coefficient was 0.157 at a high temperature of 800?during the sliding time.Although the wear rate of the samples increased with the increase of temperature,the the tribological properties of the composites with SrSO₄ were better than the unadded.When the SrSO₄ content is 10 wt%,the wear rate was on the order of 10^-6×10^-44 mm³/N·m from RT to 400?.With the addition of LaF₃,the friction coefficient and wear rate prepared by SPS remained at a low level from 200?to800?.When the content of LaF₃ is 6 wt%,the average friction coefficient was 0.189at 600?,and the average wear rate was on the order of 10^-55 mm³/N·m.Due to the salt transfer film such as SrMoO₄ and La₆MoO₁₂,the surface was prevented direct contact,and the shear strength of the contact thin layer was reduced.Thereby the stability of the composites were remarkably improved in a wide temperature range.