| 引用本文: | 方子文,何乃如,贾均红,杨杰,刘宁.等离子喷涂NiCrAlY-Cu涂层中Cu在宽温域环境下的扩散及摩擦耗散机制[J].中国表面工程,2023,36(2):65~78 |
| FANG Ziwen,HE Nairu,JIA Junhong,YANG Jie,LIU Ning.Diffusion and Friction Dissipation Mechanisms in Wide-temperaturerange of Cu in NiCrAlY-Cu Coating by Plasma Sprayed[J].China Surface Engineering,2023,36(2):65~78 |
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| 摘要: |
| 含软金属自适应涂层在摩擦过程因软金属独特的性能而具备良好的摩擦学性能，然而在不断摩擦过程中软金属会发生一定的耗散导致涂层失效。为了研究软金属润滑剂在宽温域摩擦过程中的耗散机制，利用等离子喷涂技术制备 NiCrAlY-Cu 涂层；通过分析热处理及宽温域摩擦前后涂层的组分与形貌演变，揭示 NiCrAlY-Cu 涂层中 Cu 的高温扩散及宽温域摩擦耗散机制。结果表明：Cu 以片层状分布在 NiCrAlY 基础相中，软金属 Cu 在温度单因素影响下垂直向涂层表面扩散，随着温度的升高扩散加剧。在 1 000 ℃环境下 Cu 在涂层内部发生平行扩散，并最终呈现弥散态分布。在中低温环境下随着温度的升高 Cu 的剪切强度降低进而使得涂层摩擦因数逐渐下降，但是由于 Cu 呈片层状分布，随着温度的升高涂层发生疲劳剥落导致磨损率升高。随着温度的进一步升高，Cu 扩散加剧，片层状 Cu 减少，同时发生氧化，使得摩擦因数升高，磨损率降低。在宽温域摩擦过程中由于温度和载荷的共同影响，Cu 在涂层中的摩擦耗散机制为 Cu 垂直向涂层表面扩散，由磨痕区域内向磨痕外平行扩散。同时，磨痕内聚集的 Cu 以磨屑形式逐渐损耗。提出在不同温域摩擦过程中受力-热耦合影响的软金属耗散机制， 可为解决含软金属自适应涂层的失效问题提供理论依据。 |
| 关键词: 等离子喷涂 NiCrAlY-Cu 涂层 宽温域摩擦学性能 扩散机制 摩擦耗散机制 |
| DOI：10.11933/j.issn.1007?9289.20220512002 |
| 分类号:TG174;TH117 |
| 基金项目:国家自然科学基金资助项目(51905325) |
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| Diffusion and Friction Dissipation Mechanisms in Wide-temperaturerange of Cu in NiCrAlY-Cu Coating by Plasma Sprayed |
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FANG Ziwen1, HE Nairu1, JIA Junhong1, YANG Jie1, LIU Ning2
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1.School of Mechanical and Electrical Engineering, Shaanxi University of Science and Technology,Xi’ an 710021 , China;2.Xi’ an Aerospace Composite Materials Research Institute, Xi’ an 710021 , China
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| Abstract: |
| Soft metal-containing composite coatings exhibit favorable tribological properties owing to extremely low shear strength. However, the soft metal dissipates during the friction process at elevated temperatures, resulting in the failure of such coatings. Recent studies have identified dissipation mechanisms of soft metals based on the effect of temperature. However, research on the dissipation mechanisms of soft metals by the synergetic effect of the load and temperature during the friction process at elevated temperatures has not yet been explored. NiCrAlY-Cu coatings were prepared using air plasma spraying technology to study the diffusion and dissipation mechanisms of soft metal lubrication in the composite coating by the synergetic effect of load and temperature. Heat treatment and tribological tests of the NiCrAlY-Cu coatings were carried out over a wide temperature range. The wear mechanisms of the NiCrAlY-Cu coatings are also discussed. The compositions and morphologies of the NiCrAlY-Cu coatings and worn tracks were determined using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS).The Cu content of the NiCrAlY-Cu coating was calculated and compared after heat treatment and tribological tests over a wide temperature range. The diffusion mechanisms of Cu at elevated temperatures and the dissipation mechanisms of Cu during the friction process were studied using compositional and morphological analyses. The results showed that Cu was uniformly distributed with a lamellar structure in the NiCrAlY-Cu coatings. According to the Gibbs-Thomson effect and Ostwald ripening theory, soft metal would diffuse vertically under the influence of temperature, which is consistent with Cu vertical diffusion to the coating surface. Meanwhile, the diffusion intensified as the temperature increased. Furthermore, Cu diffused in parallel and was dispersedly distributed in the NiCrAlY-Cu coating at 1 000 ℃. At low and moderate temperatures, the shear strength of Cu decreased with increasing temperature, resulting in a gradual decrease in the friction coefficients of the NiCrAlY-Cu coatings. However, fatigue spalling on the worn surface of the NiCrAlY-Cu coating caused by the lamellar distribution of Cu led to an obvious increase in the wear rate. The friction coefficient and wear rate of the NiCrAlY-Cu coatings were 0.401 and 2.49×10?3 mm3 / (N·m) at 400 °C, respectively. The wear mechanism at 400 °C is mainly severe fatigue wear. With a further increase in temperature, the intensification of Cu diffusion and oxidation in the NiCrAlY-Cu coating resulted in an increase in the friction coefficients and decrease in the wear rates. During the friction process from 25 to 1 000 °C, owing to the synergetic effect of the temperature and load, Cu diffused vertically to the coating surface according to the analysis of the Gibbs-Thomson effect, Ostwald ripening theory, and Fick’ s first law. This was further confirmed by the EDS mapping results. Moreover, Cu diffused in parallel from the inside to the outside of the worn track owing to the effect of the load. At low and moderate temperatures, the main driving force for Cu diffusion was the load effect. With a further increase in temperature, the main driving force of Cu diffusion was the temperature effect. Simultaneously, the enrichment of Cu on the worn surface gradually dissipated in the form of wear debris during the friction process. In this paper, the diffusion and dissipation mechanisms of soft metal in a soft metal-containing adaptive coating under the synergetic effect of load and temperature during the friction process over a wide temperature range are proposed, which provide a theoretical basis for solving the problem of lubrication failure of the soft metal-containing adaptive coating. |
| Key words: plasma spraying NiCrAlY-Cu coating tribological properties in wide-temperature-range diffusion mechanism friction dissipation mechanism |
