添加WS_2/MoS_2固体润滑剂的自润滑复合涂层研究进展
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摘要
自润滑复合材料由于含有固体润滑剂,可在摩擦过程中形成连续润滑膜实现自润滑特性,与传统的在摩擦界面添加以油为主的液体或半固态润滑脂的方法相比,更能适应现代真空、高温、高压、辐射等环境下的服役要求,因而得到广泛研究和关注。硫化物固体润滑剂(WS_2/MoS_2)附着性强,具有较好的成膜特性,是目前优选的固体润滑剂之一。添加WS_2/MoS_2的自润滑复合涂层的制备方法有低温湿化学法(电沉积、化学镀)和高温物理法(激光熔覆、热喷涂)。自润滑复合涂层的减摩特性与WS_2/MoS_2在涂层中的含量与分布密切相关。固体润滑剂含量太低时,不足以保证润滑膜的形成和稳定,起不到减摩作用;含量太高时,润滑剂分子堆积,易产生粘弹性摩擦阻力,甚至剥落造成恶性犁沟磨损。研究表明,固体润滑剂颗粒的团聚会导致涂层表面平整性变差、结构疏松。然而,现有工艺条件下WS_2/MoS_2固体润滑剂颗粒在涂层中的分散都达不到单分散状态。低温湿化学法具有良好的均镀能力和化学稳定性,工艺方法灵活,但微粒在镀液中的分散性有待提高,微粒在镀层中的含量需要更精准的控制。目前,可添加表面活性剂或通过金属包覆处理对粉体进行改性,以增强固体润滑剂颗粒与基体间的润湿性。迄今,无论是电沉积还是化学镀制备添加固体润滑剂的复合涂层,镀层沉积速度和镀层中WS_2/MoS_2微粒含量都随着镀液pH值、镀液中WS_2/MoS_2固体微粒含量和电流密度的增大呈现先增后减的趋势。高温物理法制备的涂层具有结合力强、密度大、硬度高的特点,目前存在的最大问题是WS_2/MoS_2超过400℃会发生分解,不仅导致润滑相减少,使涂层减摩特性受限,而且生成的气体会形成孔洞,降低涂层内聚结合力;若表面生成硬质相还会脱落造成磨粒磨损,损害涂层性能。目前,通过金属包覆WS_2/MoS_2颗粒可在一定程度上降低其分解,但也不能完全避免;也可利用WS_2/MoS_2高温分解的特点直接在熔池中生成其他润滑相,提高涂层的自润滑性能。本文综述了含WS_2/MoS_2固体润滑剂的自润滑复合涂层的制备研究进展,评价了相关工艺的优势与局限性,提出涂层中固体润滑剂含量和分布的关键影响因素以及可能的解决措施,以期为高性能自润滑复合涂层的制备和工艺优化提供参考。
Other than ordinary lubricating ways to add oil-based liquid or semi-solid grease at the friction interface,self-lubricating composite materialscan form a continuous lubricating film during friction processes to achieve self-lubricating properties with solid lubricant phase in the structure and are more adaptable to modern engineering applications such as in vacuum,high temperature,high pressure,radiation environments,etc.Due to the strong adhesion and good film forming properties,WS_2 and Mo S_2 are among the most widely used lubricating particles for preparation of self-lubricating composite coatings which can be added through a low temperature wet chemical method( electrodeposition,electroless plating) or a high temperature physical method( laser cladding,thermal spraying).The anti-friction properties of self-lubricating composite coatings are closely related to the content and distribution of WS_2/Mo S_2 in the coatings.When the content of the solid lubricant is too low,it is not enough to ensure the formation and stability of the lubricating film,so the purpose of reducing friction is not achieved. When the content is too high,the accumulation of lubricant molecules is prone to viscoelastic frictional resistance,and the coating even peels off,leading to wear mechanism of malignant furrows.Studies have shown that the agglomeration of solid lubricant particles results in poor surface flatness of the coating and loose coating. However,the dispersion of WS_2/Mo S_2 solid lubricant particles in the coating under the existing process conditions cannot reach a monodispersed state.Low-temperature wet chemical method shows good throwing ability,chemical stability,and flexibility. The limit of which is the poor dispersion of particles in the plating solution and the precise control of the particle content in the coatings.At present,the powder may be modified by adding surfactant or metal coating treatment to enhance the wettability between the solid lubricant particles and the substrate. For both electrodeposition and electroless plating,the deposition rate of metal and the content of WS_2/Mo S_2 particles in the coating are influenced by p H value and WS_2/Mo S_2 solid content in the plating solution. The coating prepared by high temperature physical method has the characteristics of good adhesion to the substrate,high density and high hardness. The biggest problem currently exists is that WS_2/Mo S_2 will decompose over 400 ℃,which not only causes the lubrication phase to decrease,but also reduces the friction reducing characteristics. Moreover,the generated gas causes pores to reduce the cohesive bonding force in the coatings,if the surface forms a hard phase,it will fall off and cause abrasive wear,which impairs the performance of the coating.At present,the decomposition of WS_2/Mo S_2 particles can be reduced by powder surface metallization,but cannot be completely avoided. The WS_2/Mo S_2 decomposition can otherwise be used to form other lubricating phases in the molten pool to improve the self-lubricating performance of the coatings.This paper reviews the progress in the preparation of self-lubricating composite coatings containing WS_2/Mo S_2 solid lubricants,evaluating the advantages and limitation of the related process factors,the key influencing factors for the content and distribution of solid lubricants in coatings and the possible solution are proposed as well.
Other than ordinary lubricating ways to add oil-based liquid or semi-solid grease at the friction interface,self-lubricating composite materialscan form a continuous lubricating film during friction processes to achieve self-lubricating properties with solid lubricant phase in the structure and are more adaptable to modern engineering applications such as in vacuum,high temperature,high pressure,radiation environments,etc.Due to the strong adhesion and good film forming properties,WS_2 and Mo S_2 are among the most widely used lubricating particles for preparation of self-lubricating composite coatings which can be added through a low temperature wet chemical method( electrodeposition,electroless plating) or a high temperature physical method( laser cladding,thermal spraying).The anti-friction properties of self-lubricating composite coatings are closely related to the content and distribution of WS_2/Mo S_2 in the coatings.When the content of the solid lubricant is too low,it is not enough to ensure the formation and stability of the lubricating film,so the purpose of reducing friction is not achieved. When the content is too high,the accumulation of lubricant molecules is prone to viscoelastic frictional resistance,and the coating even peels off,leading to wear mechanism of malignant furrows.Studies have shown that the agglomeration of solid lubricant particles results in poor surface flatness of the coating and loose coating. However,the dispersion of WS_2/Mo S_2 solid lubricant particles in the coating under the existing process conditions cannot reach a monodispersed state.Low-temperature wet chemical method shows good throwing ability,chemical stability,and flexibility. The limit of which is the poor dispersion of particles in the plating solution and the precise control of the particle content in the coatings.At present,the powder may be modified by adding surfactant or metal coating treatment to enhance the wettability between the solid lubricant particles and the substrate. For both electrodeposition and electroless plating,the deposition rate of metal and the content of WS_2/Mo S_2 particles in the coating are influenced by p H value and WS_2/Mo S_2 solid content in the plating solution. The coating prepared by high temperature physical method has the characteristics of good adhesion to the substrate,high density and high hardness. The biggest problem currently exists is that WS_2/Mo S_2 will decompose over 400 ℃,which not only causes the lubrication phase to decrease,but also reduces the friction reducing characteristics. Moreover,the generated gas causes pores to reduce the cohesive bonding force in the coatings,if the surface forms a hard phase,it will fall off and cause abrasive wear,which impairs the performance of the coating.At present,the decomposition of WS_2/Mo S_2 particles can be reduced by powder surface metallization,but cannot be completely avoided. The WS_2/Mo S_2 decomposition can otherwise be used to form other lubricating phases in the molten pool to improve the self-lubricating performance of the coatings.This paper reviews the progress in the preparation of self-lubricating composite coatings containing WS_2/Mo S_2 solid lubricants,evaluating the advantages and limitation of the related process factors,the key influencing factors for the content and distribution of solid lubricants in coatings and the possible solution are proposed as well.
引文
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2 Liu E Y,Jia J H,Gao Y M,et al.China Surface Engineering,2015,28(4),1 (in Chinese).刘二勇,贾均红,高义民,等.中国表面工程,2015,28(4),1.
3 Shi K F,Xie F.Shandong Chemical Industry,2017,46(4),55 (in Chinese).施凯烽,谢凤.山东化工,2017,46(4),55.
4 He Y,Sun W T,Wang S C,et al.Electrochimica Acta,2017,245,872.
5 Hu P,Chen Z Y,Wang K S,et al.CIESC Journal,2017,68(4),1286 (in Chinese).胡平,陈震宇,王快社,等.化工学报,2017,68(4),1286.
6 Lei S,Sun C F,Liu W M.Applied Surface Science,2008,254,6880.
7 Gustavsson F,Jacobson S.Tribology International,2006,101,340.
8 Liu H D,Yang A M,Liu F.Hot Working Technology,2018,47(2),5 (in Chinese).柳红豆,杨爱民,刘峰.热加工工艺,2018,47(2),5.
9 Xu X F.Lubrication Engineering,2010,35(11),90 (in Chinese).许小锋.润滑与密封,2010,35(11),90.
10 Sivandipoor I,Ashrafizadeh F.Applied Surface Science,2012,263,314.
11 Li W S,Cui S,He L,et al.China Surface Engineering,2017,30(3),97 (in Chinese).李文生,崔帅,何玲,等.中国表面工程,2017,30(3),97.
12 Xiang J H,Chen F C,Yan X H.Materials Protection,2001,34(4),21 (in Chinese).向军淮,陈范才,严旭辉.材料保护,2001,34(4),21.
13 Liu Y F,Zhu Y W,Liu P,et al.China Surface Engineering,2012,25(2),97 (in Chinese).刘蕴锋,朱永伟,刘平,等.中国表面工程,2012,25(2),97.
14 Lin C,Zhang H H,Li J,et al.Journal of Nanchang Hangkong University,2014,28(3),51 (in Chinese).林翠,张弘弘,李进,等.南昌航空大学学报,2014,28(3),51.
15 Cao J.Machinery Design & Manufacture,2010,51(8),123 (in Chinese).曹剑.机械设计与制造,2010,51(8),123.
16 Ying L X,Liu Y,Liu G N,et al.Rare Metal Materials and Engineering,2015,44(1),0028.
17 Liu T T,Zhu Y W,Liu Y F,et al.Lubrication Engineering,2013,38(7),46 (in Chinese).刘婷婷,朱永伟,刘蕴锋,等.润滑与密封,2013,38(7),46.
18 Balarajua J N,Kalavatib,Rajama K S.Surface & Coatings Technology,2016,200,3933.
19 Cao T K,Yang Q L,Shan C S.Lubrication Engineering,2012,37(11),55 (in Chinese).曹同坤,杨岐龙,单春生.润滑与密封,2012,37(11),55.
20 Wang Z P,Lu P C.Journal of Civil Aviation University of China,2013,31(3),54 (in Chinese).王志平,路鹏程.中国民航大学学报,2013,31(3),54.
21 Wang T G,Li B S,Yan B,et al.Journal of Materials Engineering,2017,45(3),73 (in Chinese).王铁钢,李柏松,阎兵,等.材料工程,2017,45(3),73.
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23 Jiang L,Zha B L,Wang H G,et al.Material & Heat Treatment,2009,38(2),76 (in Chinese).江礼,查柏林,王汉功,等.材料热处理技术,2009,38(2),76.
24 Zheng C,Liu X B,Yang M S.Transactions of Materials and Heat Treat-ment,2013,34(6),136(in Chinese).郑晨,刘秀波,杨茂盛.材料热处理学报,2013,34(6),136.
25 Zhang X L,Zhang X F,Wang A H,et al.China Mechanical Enginee-ring,2006,17(19),2084 (in Chinese).张祥林,章小峰,王爱华,等.中国机械工程,2006,17(19),2084.
26 Liu X B,Qiao S J,Zhai Y J,et al.Tribology,2017,37(1),75 (in Chinese).刘秀波,乔世杰,翟永杰,等.摩擦学学报,2017,37(1),75.
27 Yang J X,Liu F L,Miao X H,et al.Heat Treatment of Metals,2011,36(8),93 (in Chinese).杨胶溪,刘发兰,缪宣和,等.金属热处理,2011,36(8),93.
28 Yang J X,Liu H D,Ding X,et al.Heat Treatment of Metals,2010,35(8),22 (in Chinese).杨胶溪,刘华东,丁啸,等.金属热处理,2010,35(8),22.