ISSN   1004-0595

CN  62-1224/O4

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3种粘结固体润滑涂层的摩擦学及气蚀性能研究

Tribological and Cavitation Erosion Resistance Properties of Three Bonded Solid Lubricating Coatings

  • 摘要: 为深入研究航空燃油泵止推轴承表面用粘结固体润滑涂层在极端工况下的失效行为,采用MMW-1立式万能摩擦磨损试验机和超声振动气蚀试验机对比研究了MoS2/石墨基粘结固体润滑涂层、MoS2基粘结固体润滑涂层和石墨基粘结固体润滑涂层3种现役涂层在RP-3航空煤油中的摩擦学性能和气蚀性能;基于光学显微镜(OM)、三维光学形貌仪、扫描电子显微镜(SEM)分析了涂层原始表面以及摩擦和气蚀后表面形貌,利用高分辨X射线衍射仪(XRD)对比了摩擦前后涂层的物相组成,采用拉曼光谱仪对摩擦转移膜和涂层气蚀剥落碎屑的成分进行了表征,探讨了涂层的防护及失效机理. 结果显示:在RP-3介质中,以石墨为润滑剂的石墨基粘结固体润滑涂层摩擦系数低至0.083,磨损率为1.5×10−6 mm3/(N·m),表现出最好的摩擦学性能;3种涂层磨斑区域在摩擦前后没有出现物相变化,保持了良好的摩擦化学稳定性;对偶材料表面形成的转移膜有利于进一步降低摩擦系数. 3种涂层在煤油中的抗气蚀性能较差,表现出填料率先脱落加速涂层片状剥离的特征;因MoS2的承载能力较差且颗粒尺寸偏大,气蚀剥离程度最为严重,导致MoS2/石墨基粘结固体润滑涂层加速气蚀10 h后脱落面积高达95.83%;石墨基粘结固体润滑涂层抗气蚀性能较好,涂层脱落面积为84.73%,更适合作为止推轴承表面润滑耐磨抗气蚀涂层使用.

     

    Abstract: To focus on the in-service performance of three types of solid lubricant coatings on the surface of aero-engine fuel pump thrust bearings in aviation kerosene under simulated actual working conditions, to clarify the intrinsic mechanism of frequent flake peeling during their use, and to select a coating with superior comprehensive performance. This study also aims to provide guidance for the future development of protective coatings with better lubrication, wear resistance, and anti-cavitation erosion functions. Using an MMW-1 vertical universal tribo-wear testing machine and an ultrasonic vibration cavitation erosion testing machine, the tribological and cavitation erosion properties of three bonded solid lubricating coatings mainly based on polyamide- imide (PAI) as a binder resin, MoS2/ graphite-based bonded solid lubricating coating, MoS2-based bonded solid lubricating coating, and graphite-based bonded solid lubricating coating, in RP-3 aviation kerosene were comparatively studied. To simulate actual working conditions closely, the gear material 2Cr3WMoV was selected as the counterpart material for tribological tests. Based on optical microscopy (OM), three-dimensional optical profilometry, and scanning electron microscopy (SEM), the original surface of the coatings and the surface morphology after friction and cavitation erosion were analyzed. The phase composition of the coatings before and after friction were compared using a high-resolution X-ray diffractometer (XRD). Raman spectroscopy was used to characterize the components of the friction transfer films and the cavitation erosion peeling debris of the coatings, and the protection and failure mechanisms of the coatings were discussed. The results showed that in the RP-3 medium, with graphite as a lubricant, the friction coefficient of graphite-based bonded solid lubricating coating was as low as 0.083, and the wear rate was 1.5×10−6 mm3/(N·m), exhibiting the best tribological performance. The original solid lubricant particles embedded in the resin structure in the microstructure of MoS2/graphite-based bonded solid lubricating coating and graphite-based bonded solid lubricating coating disappeared, and a layered structure similar to scales appeared. There were no phase changes in the wear scar areas of the three coatings before and after friction, maintaining good tribological chemical stability. During the friction transfer process, the intensity ratio of D peak to G peak of graphite significantly increased, forming a graphite-like structure. The transfer films formed on the surface of the counterpart material was beneficial for further reducing the friction coefficient. The three coatings were subjected to dual attacks from cavitation load and cavitation heat in aviation kerosene, resulting in poor anti-cavitation erosion performance, showing the characteristic of "filler particles falling off first accelerating flake peeling" of the coating, and a "melt bead" structure not present in the original structure of the coating appears on the coating surface. Due to the poor load-bearing capacity and large particle size of MoS2, the degree of cavitation erosion peeling was the most serious, resulting the MoS2/ graphite-based bonded solid lubricating coating to fall off with an area of up to 95.83% after 10 hours of accelerated cavitation erosion. The anti- cavitation erosion performance of graphite-based bonded solid lubricating coating was better, with a coating fall-off area of 84.73%. The Raman spectroscopy results of the fallen debris from the three coatings indicated that cavitation erosion has little effect on the layered structure and phase composition of graphite and MoS2. In summary, we believe that the comprehensive operational performance of graphite-based bonded solid lubricating coating is more suitable for promoting the use of thrust bearing surfaces at this stage.

     

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