ISSN   1004-0595

CN  62-1224/O4

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IN718激光熔覆Co-WC/Cu复合涂层组织与摩擦学性能研究

Microstructure and Tribological Properties of Laser Cladded Co-WC/Cu Composite Coatings on IN718

  • 摘要: 为提高IN718高温合金运动部件在极端环境中的服役寿命,采用激光熔覆在其表面制备了Co (S1)、Co-5%WC-5%Cu (S2)和Co-5%WC-15%Cu (S3)(质量分数)这3种耐磨减摩复合涂层,系统分析了复合涂层的显微硬度以及室温(RT)和600 ℃环境中的摩擦学性能. 结果表明:溶解的WC重新凝固析出碳化物,起到第二相强化的作用,未溶解的WC边缘析出针状物与Co基基体稳固结合. 在室温下Cu可以充当固体润滑剂(Cu膜),在600 ℃下由CuO氧化膜以及Cu膜起减摩作用. 3种涂层的显微硬度均是基体(268.89HV0.5)的1.7倍以上,分别是478.69HV0.5、481.73HV0.5和458.51HV0.5. 摩擦学性能明显优于基体,其中S2涂层在室温和600 ℃环境下均拥有优异的耐磨性,分别提高84.4%和64.9%,减摩效果最好的是S2涂层(RT)和S3涂层(600 ℃),分别提高26.9%和26.7%. 室温下3种复合涂层的磨损行为由氧化和疲劳磨损主导,600 ℃时由氧化和黏着磨损主导.

     

    Abstract: IN718 superalloy displays outstanding comprehensive properties within a certain temperature range, but its limitations hinder the widespread apply to related moving parts in a wide temperature range. The best solution to this problem is laser cladding, which not only allows for the flexible design of high-performance coatings, but also effectively improves economic benefits. Therefore, to enhance the service life of the IN718 superalloy moving parts in extreme environments, three wear-resistant and friction-reducing composite coatings was laser-cladded onto its surface: Co (S1)、Co-5%WC-5%Cu (S2)and Co-5%WC-15%Cu (S3) (mass fraction). The microhardness of the three coatings and their tribological performance at room temperature and 600 ℃ were analyzed systematically. The results indicated that the S1 coating mainly consisted of the solid solution γ-Co and (Fe, Ni), as well as the intermetallic compound FexNby. The S2 and S3 coatings exhibited carbides such as Cr2C3 and WC, as well as a lubricating phase Cu. The dissolved WC re-solidifies and forms carbides, which enhanced dispersion, and the undissolved WC acted as a high-hardness framework that firmly combined with the coating solvent. A suitable amount of Cu could act as a solid lubricant (Cu film) at RT, and the CuO oxide film functioned as a friction reducer at 600 ℃. Additionally, both CuO and Cu films could prevent the oxidation and depletion of WC. Thus, the microhardness and tribological properties of the three coatings had been improved. The microhardness of the composite coatings were more than 1.7 times that of the substrate (268.89HV0.5), which were 478.69HV0.5、481.73HV0.5 and 458.51HV0.5, respectively. And the composite coatings also exhibited excellent tribological performance, the S2 coating showed excellent wear resistance at both RT and 600 ℃, with improvements of 84.4% and 64.9%, respectively. The S2 coating (RT) and the S3 coating (600 ℃) had the best anti-friction effects, with improvements of 26.9% and 26.7%, respectively. The main wear mechanisms of coatings were found to be oxidative and fatigue wear at RT; oxidative and adhesive wear at 600 ℃.

     

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