掺杂Ti对Ni基复合材料摩擦学性能的影响

Effect of Doping Ti on the Tribological Properties of Ni-based Composites

目的通过在NiCr-WS2自润滑体系中掺杂纳米Ti,提升自润滑复合材料在不同环境中的摩擦学性能。方法通过放电等离子烧结(SPS)技术制备了NiCr(N)、NiCr-WS2(NW)、NiCr-WS2-Ti(NW15T)3种复合材料。采用SEM和EDS分析了复合材料的微观性能。通过摩擦磨损试验机分别测试了3种材料在干摩擦、去离子水和3.5%NaCl溶液中的摩擦学性能,并借助RAMAN分析磨痕的化学成分。结果在干摩擦条件下,NW15T的摩擦因数和磨损率分别为0.38和4.2×10^(-5)mm^(3)/(N·m)。相较于传统的NW,NW15T的摩擦因数和磨损率分别降低了22.4%和83.7%;当在去离子水中摩擦时,虽然NW15T也具有较好的摩擦学性能,但是与NW相比优势不明显;在3.5%NaCl溶液中摩擦时,NW15T产生的腐蚀产物避免了摩擦副的直接接触,并使摩擦因数降低至0.16,磨损量降低为0.4×10^(-5)mm^(3)/(N·m)。与NW相比,NW15T在3.5%NaCl溶液中的摩擦因数和磨损率分别降低了38.5%和81.8%。结论在NW传统自润滑复合材料体系中掺入Ti,原位生成了TiS和Ni3Ti,不仅提高了材料的力学性能,同时提高了复合材料在不同环境下的摩擦学性能。尤其是在NaCl溶液中,在TiS和腐蚀产物的共同作用下,NW15T的摩擦因数和磨损率大幅下降。

To improve tribological properties of self-lubricating composites in different environments,nano-Ti powders were doped into NiCr-WS2.Then,spark plasma sintering(SPS)was used to prepare NiCr(N),NiCr-WS2(NW),NiCr-WS2-Ti(NW15T)composites.In this study,SEM and EDS were utilized to analyze the microstructure of materials.Meanwhile,the tribological properties of materials at dry friction,deionized water,3.5wt.%NaCl solution,were tested by MFT-5000 tribometer with reciprocating motion at room temperature.Besides,Raman spectra of the wear tracks were recorded by a Raman spectrometer system.Due to better mechanical properties and TiS,NW15T exhibited good tribological properties during dry friction,and the results show that friction coefficient and wear rate of NW15T are 0.38 and 4.2×10^(-5)mm^(3)/(N·m)at dry friction condition.For NW,due to the poor interfacial bonding strength between CrS and the substrate,cracks are easily initiated at the interface during the friction process.At the same time,the uniformly dispersed CrS promotes the crack propagation,resulting in the wear rate of NW as high as 25.7×10^(-5)mm^(3)/(N·m)at dry friction condition.Compared with NW,the friction coefficient and wear rate of NW15T reduced by 22.4%and 83.7%,respectively.Different from dry friction,owing to the good lubrication of water all materials exhibited excellent tribological properties when sliding in water.Furthermore,the frictional heat is easily dissipated in water,so that no obvious cracks and spalling pits were seen on the surface of materials after sliding in water.However,there are obvious grooves on the surfaces of materials,which means the wear mechanism of materials is abrasive wear when they sliding in water.Nonetheless,NW15T exhibits better tribological performance in deionized water than N and NW.It is worth noting that the friction coefficient and wear rate of NW15T are only 0.16 and 0.4×10^(-5)mm^(3)/(N·m)when sliding in NaCl solution,due to the fact that the corrosion products of NW15T avoid direct contact for the friction pair.Compared with NW,the friction coefficient and wear rate of NW15T in 3.5wt.%NaCl solution are reduced by 38.5%and 81.8%,respectively.Furthermore,the wear of coupled ball of NW15T is much smaller than that of N and NW.In order to study the wear mechanism of NW15T in more detail,Raman be used to analyze the corrosion products of NW15T.It is found that the main corrosion products of NW15T are not only contain NiO and Cr2O3but also TiO2.This is because NW15T has a large area of TiS,and the Ti rich area is easily corroded in NaCl solution to form TiO2.These corrosion products are easily transferred to the counter balls during sliding,thereby reducing the friction coefficient and wear rate of NW15T.In summary,nano Ti powders were added to NW,and lead to formation of TiS and Ni3Ti,which promotes the improvement of lubrication and wear resistance.Especially in NaCl solution,the friction coefficient and wear rate of NW15T are greatly reduced under the synergistic effect of TiS and corrosion products.