基于纳米颗粒的镁合金轧制润滑剂的摩擦学特性及机理研究

发布时间：2018-09-19 16:52

【摘要】：镁合金具有质轻、比强度高、阻尼减震和电磁屏蔽性好等优点,在航空航天、电子产品、汽车等领域受到越来越多的关注,并得到较为广泛的应用。轧制是镁合金的一种重要的变形加工方式。目前,镁合金在轧制过程中通常采用铝合金轧制液,甚至进行无润滑轧制。轧制过程中无润滑液会导致镁合金轧板表面质量差、能耗高,而铝合金轧制液通常含有氯、硫、磷等有机化合物和金属盐等添加剂,此类添加剂不容易分解,使用后废液的排放会对环境造成一定污染。本文通过摩擦磨损试验对镁合金在纳米基润滑剂润滑条件下的摩擦学性能进行测试。采用激光共聚焦显微镜、场发射扫描电镜(FESEM)、X射线光电子能谱(XPS)等手段,考察磨痕表面形貌和化合物组成成分,探讨添加剂之间以及添加剂与金属表面之间的作用机理。然后将摩擦磨损试验筛选的纳米基润滑剂进行AZ31镁合金板材轧制,观察在干轧和纳米基润滑剂润滑条件下轧制力的变化和轧制板材表面质量的不同。主要结果如下:(1)考察了MoS_2纳米颗粒添加到5#机械油(无其他添加剂)、菜籽油和30#机械油(含添加剂)三种不同基础油中的摩擦学性能,探索MoS_2纳米颗粒与不同基础油及摩擦副表面的作用机理。结果表明,MoS_2纳米颗粒添加到5#机械油和菜籽油中均有一定的减摩抗磨作用,MoS_2纳米颗粒加入5#机械油中的减摩抗磨性能优于加入菜籽油中。而MoS_2纳米颗粒加入30#机械油中的减摩抗磨性能与不含MoS_2纳米颗粒的30#机械油的减摩抗磨效果相当。(2)通过控制纳米颗粒在基础油中的含量和摩擦测试参数,从纳米颗粒成分含量、承载能力及润滑膜稳定性三个方面考察了SiO_2和MoS_2分别作为润滑油添加剂对镁合金的摩擦磨损性能的影响。结果表明,SiO_2纳米基润滑油较MoS_2纳米基润滑油具有更优的减摩性能,而MoS_2纳米基润滑油较SiO_2纳米基润滑油具有更优的抗磨性能、承载能力和润滑膜稳定性。基于以上研究基础,然后研究了SiO_2纳米颗粒和MoS_2纳米颗粒复合作为润滑油添加剂,进一步优化了两种纳米颗粒单独作为润滑添加剂的润滑性能,并深入探讨了两种纳米颗粒复合添加的协同润滑机理。(3)通过摩擦磨损试验系统考察了石墨烯、氧化石墨烯单独添加以及石墨烯和氧化石墨烯分别与SiO_2纳米颗粒复合添加作为水基润滑添加剂对镁合金的摩擦磨损性能的影响。氧化石墨烯作为水基润滑添加剂的润滑性能优于石墨烯作为润滑添加剂。石墨烯与SiO_2纳米颗粒复合添加起到了协同润滑作用比单独石墨烯作为润滑液添加剂的润滑性能优异。而氧化石墨烯与SiO_2纳米颗粒复合添加与单独氧化石墨烯作为润滑添加剂的润滑性能相当。即使这样,在复合物中SiO_2纳米颗粒取代了部分氧化石墨烯降低了生产成本。(4)将通过摩擦磨损实验筛选出来的润滑性能优良的SiO_2/MoS_2复合油基润滑液、SiO_2/石墨烯复合水基润滑液和SiO_2/氧化石墨烯复合水基润滑液在AZ31镁合金轧制过程中应用。相对于干轧来说,在SiO_2/MoS_2复合油基润滑液润滑条件下压下量为10%对AZ31镁合金轧制,轧制力和轧后板材表面粗糙度分别降低了14.5%和55.9%。石墨烯/SiO_2复合水基润滑液润滑条件下,轧制力和轧后板材表面表面粗糙度相对于干轧分别降低了12%和42.4%。氧化石墨烯/SiO_2复合水基润滑液润滑条件下,轧制力和轧后板材表面表面粗糙度相对于干轧分别降低了13.1%和28.8%。(5)总结认为,SiO_2/MoS_2复合油基润滑液和SiO_2/石墨烯复合水基润滑液中两种纳米颗粒起着协同润滑作用,均比单独一种纳米颗粒作为润滑添加剂的润滑性能优异。而氧化石墨烯/SiO_2纳米复合水基润滑液的润滑性能与纯氧化石墨烯水基润滑液的润滑性能相当,但其作为润滑液比纯氧化石墨烯润滑液的成本降低。
[Abstract]:Magnesium alloys have attracted more and more attention in aerospace, electronic products, automotive and other fields because of their advantages of light weight, high specific strength, good damping and electromagnetic shielding. Rolling is an important deformation processing method of magnesium alloys. At present, aluminum alloy is usually used in the rolling process of magnesium alloys. In the rolling process, no lubricant will lead to poor surface quality and high energy consumption of magnesium alloy rolling plate, while aluminum alloy rolling fluid usually contains chlorine, sulfur, phosphorus and other organic compounds and metal salts additives, such additives are not easy to decompose, waste liquid discharge after use will cause certain environmental pollution. The tribological properties of magnesium alloys lubricated with nano-based lubricants were tested by friction and wear tests. The surface morphology and composition of the wear scars were investigated by means of laser confocal microscopy, field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and the relationship between additives and metal surface was discussed. The main results are as follows: (1) The addition of MoS_2 nanoparticles to 5# mechanical oil (without other additives) was investigated. Tribological properties of rapeseed oil and 30 # mechanical oil (containing additives) were investigated to explore the mechanism of action of MoS_2 nanoparticles on the surfaces of different base oils and friction pairs. The friction and anti-wear properties of MoS_2 nanoparticles in 30# mechanical oil are similar to those of 30# mechanical oil without MoS_2 nanoparticles. (2) By controlling the content of nanoparticles in the base oil and the friction test parameters, the content of nanoparticles, the load-carrying capacity and the lubricating film are stable. The effects of SiO_2 and MoS_2 as lubricating oil additives on the friction and wear properties of magnesium alloys were investigated qualitatively in three aspects. The results showed that SiO_2 nano-based lubricating oil had better antifriction performance than MoS_2 nano-based lubricating oil, and MoS_2 nano-based lubricating oil had better antiwear performance, load-bearing capacity and wear resistance than SiO_2 nano-based lubricating oil. Based on the above research, the lubrication performance of SiO_2 nanoparticles and MoS_2 nanoparticles as lubricant additives was further optimized, and the synergistic lubrication mechanism of the two nanoparticles was discussed in detail. (3) Friction and wear of the lubricant were studied. The effects of graphene, graphene oxide and graphene oxide and SiO_2 nanoparticles on the friction and wear properties of magnesium alloys were investigated. The lubrication performance of graphene oxide as water-based lubrication additive was better than that of graphene as lubrication additive. The lubrication performance of graphene oxide and SiO_2 nanoparticles is comparable to that of graphene oxide alone. Even so, SiO_2 nanoparticles replace SiO_2 nanoparticles in the composites. (4) SiO_2/MoS_2 composite oil-based lubricants, SiO_2/graphene composite water-based lubricants and SiO_2/graphene oxide composite water-based lubricants with excellent lubrication performance screened by friction and wear tests were used in the rolling process of AZ31 magnesium alloy. Compared with dry rolling, SiO_2/MoS_2 composite lubricants were used in the rolling process of AZ31 magnesium alloy. The rolling force and surface roughness of AZ31 magnesium alloy after rolling were reduced by 14.5% and 55.9% respectively by 10% reduction under the lubricating condition of compound oil-based lubricant. The rolling force and surface roughness of AZ31 magnesium alloy after rolling were reduced by 12% and 42.4% respectively compared with that of dry rolling under the lubricating condition of graphene/SiO_2 compound water-based lubricant. The rolling force and the surface roughness of rolled sheet decreased by 13.1% and 28.8% respectively compared with dry rolling under O_2 complex water-based lubricant lubrication condition. (5) It is concluded that SiO_2/MoS_2 complex oil-based lubricant and SiO_2/graphene complex water-based lubricant play a synergistic lubrication role, both of which are better than single nanoparticle as lubricant. The lubrication performance of graphene oxide/SiO_2 nanocomposite water-based lubricant is similar to that of pure graphene oxide water-based lubricant, but its cost is lower than that of pure graphene oxide lubricant.
【学位授予单位】：重庆大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG339;TH117.22

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