Study On The Preparation And Tribological Behavior Of NiCr-V₂AlC-MoS₂ Composites

In aerospace,military industry,automotive electronics and other special working conditions,more and more attentions have been paid to how to reduce friction and wear and obtain good self lubrication effect in wide temperature range.In this paper,V₂AlC and MoS₂ were added to the Ni-Cr alloy as the addition phase to improve the friction property of the alloy and the wear mechanism of the composites were analyzed In this paper,V₂Al C powders were synthesized by solid state reaction.The optimum molar ratio of V:Al:C=2:1.2:0.9 was obtained.At the same time,the synthesis route of V₂AlC powder was deduced by exploring the reaction products of raw powder at different temperatures.Ni-Cr alloy,NiCr-V₂AlC composites with different V₂AlC and NiCr-V₂AlC-MoS₂composites were fabricated by spark plasma sintering.The microstructure,mechanical properties,friction and wear properties of the matrix and composites were characterized.The effects of V₂AlC and MoS₂ on the tribological properties of the composites were analyzed,and the nature of tribological properties of composites at different temperature was revealed.The friction coefficient and wear rate of the matrix were higher.Matrix friction coefficient was 0.8-0.9 and the wear rate was 3×10^-44 mm³/?Nm?at room temperature and 200 ?.When the temperature increased to 400 ? and 600 oC,the friction coefficient decreased to 0.4-0.5,and the wear rate decreased to 1×10^-44 mm³/?Nm?.The tribological properties of NiCr-V₂AlC composites show that the addition of V₂AlC can play a role of lubrication,and the tribological properties of 30 wt.%V₂AlC composites were best.The friction coefficient was about 0.6 at room temperature and200 ?,and the wear rate reduced to 3×10^-55 mm³/?Nm?.The friction coefficient decreasesd to about 0.5 and the wear rate decreased to 8×10^-66 mm³/?Nm?,At 400 ? and600 ?,the addition of V₂AlC reduced the wear rate of the composite by an order of magnitude.The addition of V₂AlC increased the strength of the matrix,and the high strength of the composite material at low temperature reduced the friction and wear.At higher temperatures,the composite materials produced a large amount of oxides include NiO,Cr₂O₃,V₂O₃,V₂O₅,Al₂O₃ and NiCr₂O₄.These oxides form a layer of glaze on the wear surface,significantly reduced the friction coefficient and wear rate of the composites.The NiCr-V₂AlC-MoS₂ composites were prepared by adding 10 wt.%MoS₂ on the basis of the optimized NiCr-30V₂AlC composites,which could further reduce the friction and wear of the composites.The friction coefficient of composites decreased to0.5 at room temperature and 200 ?,and the wear rate decreased to 2-8×10^-66 mm³/?Nm?;the friction coefficient decreased to about 0.4 at 400 ? and 600 ?,and the wear rate was about 9×10^-66 mm³/?Nm?.The soft sulfides lubrication layer formed on the worn surface played a role in lubricating at low temperature,good friction properties under high temperature was due to the glaze layer,formed on the wear surface by NiO,V₂O₅,V₂O₃,MoO₃,Al₂O₃ oxides...