无机类富勒烯二硫化钼的制备及其复合镀层的摩擦磨损性能

【作者】 邹同征；

【导师】 涂江平；

【作者基本信息】 浙江大学 ， 材料学， 2006， 硕士

【摘要】 本文以金属表面低摩擦和高耐磨性能的材料为应用背景,对具有良好环境稳定性的固体润滑剂无机类富勒烯二硫化钼的合成方法、钢基体上的镍基复合镀层的制备工艺及其摩擦磨损性能进行了研究,并讨论了无机类富勒烯二硫化钼的形成机理及其在复合镀层摩擦磨损中的作用机制。 通过添加分散剂聚乙二醇,采用简单的化学沉淀法先获得了非晶球状前驱体三硫化钼,将前驱体在900℃下用氢气脱硫并保温8h结晶,制备了无机类富勒烯二硫化铝（IF-MoS₂）纳米颗粒。利用X射线衍射（XRD）、扫描电子显微镜（SEM）、高分辨透射电子显微镜（HRTEM）和粒度分析仪对颗粒的微观结构和形貌进行了观察表征,考察了分散剂、脱硫温度和保温时间对IF-MoS₂形成的影响。通过添加分散剂,防止了球状前驱体在高温脱硫阶段的团聚现象,得到的MoS₂颗粒粒径随分散剂量的增加而减小;脱硫时,随着温度和保温时间的延长,MoS₂颗粒的结晶度提高,但颗粒大小和形状保持不变,直到过热时大部分颗粒会转变成层状结构的MoS₂。 利用化学共沉积法在钢基体上制备了Ni-P-（IF-MoS₂）复合镀层,在400℃下真空处理2h。采用X射线衍射分析了复合镀层退火前后的组织结构变化,光学显微镜测量了复合镀层的厚度,扫描电子显微镜对复合镀层的表面形貌进行了观察,利用质量法估算了IF-MoS₂纳米颗粒在复合镀层中的体积分数。复合镀层的沉积速率比纯镍镀层的沉积速率高,且随镀液中IF-MoS₂浓度的增加,复合镀层的沉积速率逐渐提高;复合镀层中IF-MoS₂颗粒的体积分数也随镀液中IF-MoS₂浓度的增加而提高,并逐渐趋于饱和;经退火处理后,镀层由非晶态转变成晶态,伴有Ni₃P硬质相产生;复合镀层表面相对较光滑,IF-MoS₂纳米颗粒在镀层中分散良好,并均匀嵌入在复合镀层中。 用维氏硬度计和涂层附着力自动划痕仪分别测试了化学沉积Ni-P-（IF-MoS₂）复合镀层的硬度和结合力,用销—盘式摩擦试验仪和球—盘式微摩擦磨损试验机评估了复合镀层的滑动摩擦性能,并采用扫描电子显微镜观察了复合镀层的表面磨损形貌。实验结果表明:复合镀层的硬度较高,与基体的结合力良好,硬度随镀层中IF-MoS₂纳米颗粒体积分数的增加而提高;复合镀层摩擦系数和磨损率也较小,并随IF-MoS₂纳米颗粒体积分数的增加而降低;与Ni-P-（2H-MoS₂）复合镀层相比较,Ni-P-（IF-MoS₂）复合镀层具有更好的摩擦磨损性能和环境稳定性。说明IF-MoS₂纳米颗粒在复合镀层中的均匀分布对镀层起到了强化作用,提高了镀层的硬度,同时由于其特殊的形状和结构,具有良好的环境稳定性,在摩擦磨损过程中,还起到了抗磨减摩作用。Ni-P-（IF-MoS₂）复合镀层是一种具有优异摩擦磨损性能和良好环境稳定性的先进复合材料。更多还原

【Abstract】 Upon the application background of solid lubricants and wear resistant materials, the synthesis of inorganic fullerene-like MoS₂ as a solid lubricant, the preparation and tribological properties of Ni-P-（IF-MoS2） composite coatings on medium carbon steel substrates were investigated. The formation mechanism of IF-MoS₂ was discussed and the effects of IF-MoS₂ on the friction and wear properties were also evaluated.Amorphous MoS₃ precursor was prepared by precipitation method with addition of polyethylene glycol （PEG） as surface dispersant agent, and then IF-MoS₂ nanoparticles were obtained by desulphurizing the precursor in a mixed gas of hydrogen-argon at 900°C for 8h. The as-prepared IF-MoS₂ nanoparticles were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, high resolution transmission electron microscopy （HRTEM） and particle size analyzer. The formation mechanism of IF-MoS₂ was discussed including the influence of the surface dispersant agent, the temperature and the holding time. It can be found that addition of PEG could disperse the precursor and prevent the agglomeration of MoS₂ nanoparticles during desulphurizing. The average diameter of MoS₂ decreased with increasing the mass of PEG With increasing the desulphurizing temperature and prolonging the time, the crystallization of MoS₂ particles went better while the size and the morphology of the particles remained unchanged. However, when it was overheated, most of the spherical particles changed to layered structures.Ni-P-（IF-MoS2） composite coatings were deposited on medium carbon steel substrate by electroless plating and then treated at 400°C for 2h. Microstructure of the composite coatings before and after treatment was identified by X-ray diffraction （XRD） and the surface morphology of the composite coatings was characterized by scanning electron microscopy （SEM）. The thickness and the mass of composite coatings were measured by optical microscope and electronic balance and by comparing with the density of Ni-P coating the volume fractions of IF-MoS₂ in the composite coatings were calculated. It can be found that the plating speed and the volume fraction of IF-MoS₂ in the composite coatings increased with increasing the concentration of IF-MoS₂ nanoparticles in the plating bath. After annealing the microstructure of the coatings changed from amorphous feature to crystalline nickel and Ni₃P phase was formed. The surface of the composite coating was relatively smooth and IF-MoS₂ nanoparticles appeared well dispersed and were embedded in the nickelmatrix.Microhardness of the composite coatings and the adhering force with the substrates have been determined with Vickers hardness indenter and scratch tester. The results indicated that Ni-P-（IF-MoS2） composite coatings revealed high microhardness and the hardness increased with increasing the volume fractions of IF-M0S2 nanoparticles, and the composite coatings adhered well to the substrates. Friction and wear properties of the coatings were investigated using pin-on-disk and ball-on-disk wear testers, respectively, and the morphology of the worn surfaces was characterized by scanning electron microscopy （SEM）. The friction coefficients of the composite coatings were low. The wear rate and the friction coefficient of the composite coatings showed a steadily decreasing trend with increasing the volume fraction of IF-M0S2. The favorable effects of IF-M0S2 on wear resistance and antifriction are attributed to their unique fullerene-like structure. Ni-P-（IF-MoS2） composite coatings also exhibited good tribological properties both in humid air and vacuum, implying the good stability of IF-M0S2 in different environments.更多还原