Study On Mechanical Properties, Tribological Properties And Mechanism Of Wide Temperature Range Continuous Lubricating Ni-based Materials

With the rapid development of aerospace,nuclear engineering and other modern high-tech industries,there is an urgent need for materials with high strength and continuous lubrication function in a wide temperature range.In this paper,the design,preparation and comprehensive properties of Ni-based high strength continuous lubrication materials are studied.Several Ni-based composites were prepared by powder metallurgy.The effects of lubricating phases（MoS₂,Ag）,alloying elements（Ta）and their interaction on the microstructure,mechanical properties and tribological properties in a wide temperature range（room temperature⁸00℃）,and the mechanism of lubrication and fracture of the materials at different temperatures were studied.The main results are as follows:The effects of MoS₂,Ag and Ag/MoS₂ on the friction and wear properties of NiMoAl alloy in wide temperature range were studied.The results showed that the friction coefficient of the composite decreased with the increase of temperature,but the wear rate increased abnormally at 400℃,and then decreased below 5×10^-5mm³/Nm.NiMoAl-MoS₂-Ag composite has low friction coefficient and wear rate at medium and high temperature,and shows the best tribological performance at 800℃(friction coefficient is 0.22,wear rate is 1.68×10^-5 mm³/Nm),which is attributed to the formation of a synergistic lubricating film composed of metal oxide,a variety of molybdate and Ag on the wear surface at high temperature.The effects of MoS₂ and Ag solid lubricants on the tensile and compressive properties of NiMoAl alloy in wide temperature range were studied.The results show that the addition of lubricants can reduce the tensile and compressive strength of the composite.NiMoAl and NiMoAl-Ag alloys show microporous polymerization fracture,while NiMoAl-MoS₂ and NiMoAl-Ag-MoS₂ composites show intergranular fracture.The effects of Ta and Ag on the tribological properties of NiCrMoAl alloy in wide temperature range were studied.The results showed that the addition of Ta reduced the friction coefficient in wide temperature range and the wear rate at medium and high temperature,which was mainly related to the TaC ceramic phase formed after sintering.The NiCrMoAl-Ta-Ag composite realized the tribological properties in the range of RT to 800℃.At room temperature,Ag provides lubrication;at medium temperature,the wear debris and Ag form local lubrication film;at 800℃,the best friction and wear effect(0.24,3×10^-5 mm³/Nm)is obtained,which is attributed to the formation of a synergistic lubrication film composed of oxide,silver molybdate and Ag on the wear surface at high temperature,which reduces the friction coefficient and wear rate of the composite at medium and high temperatureThe influence of alloy elements Ta and solid lubricant Ag on the tensile and compressive properties of NiCrMoAl alloy in a wide temperature range was studied.The results showed that TaC hard phase was formed in-situ during the preparation of the material with Ta,which improved the sintering performance of the material;NiCrMoAl-Ta composite in a wide temperature range（RT¹000℃）and NiCrMoAl-Ta-Ag has good high temperature mechanical strength.The excellent mechanical properties are attributed to the dispersion and composite strengthening of TaC and Al₂O₃ ceramic phases formed in-situ during sintering.The fracture mechanism changed from microporous aggregation fracture to microporous aggregation and oxidation failure fracture with the increase of temperature.