| 引用本文: | 欧正雄,夏岳,王凯悦,宋惠,西村一仁,李赫.金刚石涂层的干摩擦性能及在机械密封应用[J].中国表面工程,2024,37(6):257~270 |
| OU Zhengxiong,XIA Yue,WANG Kaiyue,SONG Hui,KAZUHITO Nishimura,LI He.Dry-friction Properties of Diamond Coatings in Mechanical-seal Applications[J].China Surface Engineering,2024,37(6):257~270 |
|
| 摘要: |
| 机械密封件是阻止旋转设备中介质泄漏的关键部件，在机械行业中广泛应用。随着服役工况日益苛刻，密封界面出现摩擦加剧（如高温、高速以及启 / 停阶段下出现干摩擦）、泄漏量增多以及寿命降低等问题，直接影响了关键密封摩擦部件的服役性能。通过机械密封部件工作面引入表面防护涂层可以极大改善密封界面的润滑行为，提升服役寿命。化学气相沉积 （CVD）金刚石涂层兼具优异的力学性能与化学稳定性，是典型陶瓷密封环理想的端面防护材料。首先通过采用热丝化学气相沉积（HFCVD）在 SiC 陶瓷密封环上分别设计制备微米金刚石（MCD）涂层和超细纳米金刚石（UNCD）涂层，在自主搭建的高性能机械密封测试设备上进行不同晶粒尺寸金刚石涂层改性密封环的摩擦学行为测试。试验表明：①金刚石涂层改性机械密封环与 SiC 陶瓷密封环相比，摩擦因数降低 4~5 倍，磨损率降低 20 倍（其中 MCD 涂层摩擦因数约为 0.24，磨损率为 0.67×10?6 mm3 / (N·m)；UNCD 涂层摩擦因数约为 0.22，磨损率为 3.43×10?6 mm3 / (N·m)）；②与 UNCD 涂层相比， MCD 涂层在相同干摩擦环境下具有较高的膜基结合力与抗磨损性能，但摩擦因数较高。随后通过引入研磨抛光手段降低制备金刚石涂层的表面粗糙度，系统探究研磨抛光后 MCD 涂层和 UNCD 涂层在干摩擦环境下的摩擦磨损性能。通过研磨抛光降低 MCD 涂层表面粗糙度后可有效改善其摩擦因数，与摩擦稳定时 UNCD 摩擦因数 0.07 保持一致，其中 SiC 球磨损率从 3.21×10?6 mm3 / (N·m)降低到 0.09×10?9 mm3 / (N·m)。这与 MCD 涂层经过表面粗糙度优化后，有效改善干摩擦过程中磨粒磨损与黏着磨损有关。上述研究不仅为金刚石涂层在干摩擦环境中改性与摩擦机理分析提供了简洁有效的思路，同时进一步扩展了 MCD 作为防护涂层在机械密封中的应用。 |
| 关键词: 机械密封 微米金刚石(MCD)涂层 超细纳米金刚石(UNCD)涂层 研磨 抛光 干摩擦 表面防护 摩擦机理 |
| DOI：10.11933/j.issn.1007-9289.20231229005 |
| 分类号: |
| 基金项目:国家重点研发计划（2022YFB3706200）；宁波科技创新 2025 重大项目（2023Z009）；中国科学院青年培育基金（JCPYJJ-22030）；国家自然科学基金（U21A2073） |
|
| Dry-friction Properties of Diamond Coatings in Mechanical-seal Applications |
|
OU Zhengxiong1，2，XIA Yue2，WANG Kaiyue1，SONG Hui2，KAZUHITO Nishimura2，LI He2
|
|
1.School of Materials Science and Engineering, Taiyuan University of Science and Technology,Taiyuan 030027 , China ；2.Key Laboratory of Advanced Marine Materials, Ningbo Institute of Materials Technology and Engineering,Chinese Academy of Sciences, Ningbo 315201 , China
|
| Abstract: |
| Mechanical seal is crucial for preventing medium leakage in rotating equipment and is widely used in the mechanical industry. Seal-interface friction damage is accelerated under certain conditions (e.g., high temperature, high speed, and start /stop-stage dry friction), which increases leakage, reduces lifetimes, and other problems that directly affect the service performance of key seal friction components. Diamond coatings deposited via chemical vapor deposition are the best sealing material for conventional ceramic seals owing to their excellent properties, which are similar to those of natural diamond, e.g., high hardness, low friction and wear resistance, high thermal conductivity, and high corrosion resistance. In this study, diamond coatings are deposited on SiC seal-ring and sheet substrates via hot-filament chemical vapor deposition (HFCVD). Microcrystalline diamond (MCD) and ultrafine nanocrystalline diamond (UNCD) coatings are applied to SiC ceramic seals. The friction of diamond-coated seals with different grain sizes is evaluated by a high-duty mechanical seal-ring evaluation equipment. The results show that the friction factor of the MCD is approximately 0.24, and the wear rate is 0.67×10?6 mm3 / (N·m), and the friction factor of the UNCD is approximately 0.22, and the wear rate is 3.43×10?6 mm3 / (N·m). The friction factor of the diamond-coated modified mechanical seal ring is 4 to 5 times lower than the conventional SiC ceramic seals, and the wear rate is about 20 times lower than the conventional SiC ceramic seals. Compared with the UNCD coating, the MCD coating demonstrates higher adhesion and wear resistance in the same arid friction environment, albeit with a slightly higher factor of friction. Dry-friction test results of the mechanical seal ring show severe adhesive wear in the dry-friction process between SiC and SiC sealing rings, which contributed to the large friction factor and severe wear of SiC sealing rings. When the diamond-coated sealing ring is paired with the SiC sealing ring, adhesive wear is avoided owing to the high hardness of the diamond coating. The diamond-coated sealing ring is paired with a SiC sealing ring, which avoids adhesive wear due to the high hardness of the diamond coating, whereas low wear is achieved by sacrificing the softer SiC sealing ring during the dry-friction process. The low factor of friction of the UNCD is due to the low adhesion of the grains. When the frictional resistance is high, the frictional resistance can be reduced by reducing the larger obstructed grains; simultaneously, the contact surface is smoothed promptly and the surface roughness is reduced, thus resulting in a lower friction factor and a greater amount of wear. To investigate the effect of diamond coatings with different grain structures and surface roughness on dry-friction properties, grinding and polishing techniques are adopted to reduce the surface roughness of the diamond coatings, and X-ray diffraction (XRD) is performed to confirm that the grain structure does not change before and after grinding and polishing. The friction and wear properties of the MCD and UNCD diamond coatings after grinding and polishing are systematically evaluated by friction experiments. The results show that the factor of friction of the MCD coating improved significantly by refining the surface roughness via grinding and polishing, and that the factor of friction is consistent with that of the stable UNCD measurement, i.e., 0.07. Additionally, the wear rate of silicon-carbide balls decreases from 3.21×10?6 to 0.09×10?9 mm3 / (N·m), which is attributed to the optimization of surface roughness during dry friction and improved MCD effects after abrasive and adhesive wear, which effectively broadens the utilization range of MCD as a defensive coating for mechanical seals. |
| Key words: mechanical seal microcrystalline diamond (MCD) coating ultrafine nanocrystalline diamond (UNCD) coating grinding polishing dry friction surface protection friction mechanism |
