The Research On Ni-based Materials With High Strength And Continuous Self-lubricating Performance In Wide Temperature Range

With the development of high-tech modern industries,including aerospace engineering,nuclear engineering,ect,there are urgent requirements for the high-performance lubrication and high-strength matericals serving under such extreme working conditions.Especially for the high temperature machine represented by advanced engines,the demand for matericals with high strength as well as good tribological properties from RT to 1000 ?.Series of Ni-based alloys and Ni-based composites materials were fabricated by powder metallurgy method(high-energy ball milling and vacuum hot pressing sintering).The effect of alloy elements and lubricants on the mechanical properties and tribological properties of Ni-based material were investigated,the lubrication mechanism in wide temperature were revealed.The main results were as follow:The influence of molybdenum incorporation in NiCrAl alloy was studied,the results shown that appropriate amount of molybdenum element can improve the mechanical properties and tribological properties of NiCrMo alloy.The compression property,hardness and density at room temperature were increased with the increasing of Mo contents,while,NiCrAl5 Mo have the best mechanical properties in the wide temperature except at 600 ?,this phenomenon appeared abnormal at 600 ?,the possible reason was that Mo2 C play a solid strength role at this temperature.The tribological properties were improved with the increased of temperature,the excellent tribological properties and mechanical properties were acquired when the content of Mo was 5wt.%,and the friction coefficient is as low as 0.22,and the wear rate reached to 10-6mm3/(Nm)at 900 ?,the good tribological properties were attributed to the formation of tribo-layers consisted of of NiO and NiMoO4.The addition of Al element can improve both the compactness and hardness of the NiCrMoAl alloy and restrained the grain growth in the sintering process.Meanwhile it can also reduce the agglomeration of the alloy powder.During high temperature friction process,the formation of tribo-layer with MoO3?NiO and NiMoO4 on the worn surface in the process of friction and reduce the formation of Cr2O3 compared with that of NiCrMoAl alloy,eventually development the wear properties of the system heavily.The effect of Ag/MoS2 on the mechanical properties and tribological properties in the wide temperature(RT~900 ?)of Ni-based alloy were studied.The results show that the addition of 10 wt.%Ag in NA alloy significantly lead to a decrease in the friction coefficients from room temperature to 900?,but have a adverse effect on the wear rate at room temperature,in high temperature,NiO,MoO2,MoO3 and Ag2MoO4 were produced by tribochemical reaction on the worn surfaces during sliding process,those lubricants play an important role in improving the friction and wear resistance properties of the alloy,the best friction coefficient were observed for NA alloy,which were attributed to the formation of synergistic lubricating film NiO,MoO2,MoO3 and Ag2MoO4 on the worn surface.The addition of 10 wt.%MoS2 in NM composite significantly lead to a decrease in the friction coefficients and wear rate from room temperature to 500 ?,which was attributed to the formation of synergistic lubricating film NiS,NiO,MoO2,MoO3 and NiMoO4 on the worn surface,but the friction coefficient of NM composite were not obviously deceased above 700 ?.The best friction coefficients obtained when addition of 10 wt.% Ag and 10 wt.%MoS2 simultaneously of NAM composite from room temperature to 900 ?,Ag2Mo2O7 which produced by tribochemical reaction at 900 ?,the best friction coeffiction was observed for the NAM composite which due to the synergistic effects of Ag,NiS,NiO,MoO2,MoO3,NiMoO4,Ag2MoO4,Ag2Mo2O7 at different temperature.