【作者】 任元；

【导师】 莫继良；

【作者基本信息】 西南交通大学 ， 机械工程， 2011， 硕士

【摘要】 物理气相沉积(简称PVD)技术制备的CrN涂层以及CrN加入Al后形成的三元Cr-Al-N系涂层具有优良的综合性能,已被成功用于刀具、模具、轴承和活塞环等耐磨零件表面,其中高A1含量的AlCrN涂层由于其优越的抗高温氧化和磨粒磨损性能更是成为新一代三元PVD氮化物涂层最典型的代表。转动微动磨损是在交变载荷下接触副发生转动的相对运动所造成的磨损。转动微动现象广泛的存在于工业设备、民用机械及医疗器械中,其造成的事故比比皆是,每年由于转动微动磨损带来的损失不可估量。涂层材料对微动磨损与疲劳有很好的防护作用,而CrN和AlCrN涂层作为耐磨涂层用于解决转动微动模式下磨损问题有着很大的前景,如应用在高档主轴承和球阀等零部件中表现出了优异的耐磨性,然而迄今为止关于这两种涂层的转动微动摩擦磨损特性的研究鲜见报道。本文利用新型转动微动磨损试验装置,采用球／平面接触,对磨副为Si3N4陶瓷球,研究了物理气相沉积制备的CrN和AlCrN涂层在不同法向载荷(Fn=10N、20N、40N)和不同转动角位移幅值(θ=0.125°、0.25°、0.5°、1°、2°)条件下的转动微动摩擦磨损行为。在分析摩擦动力学行为的基础上,用扫描电子显微镜(SEM)、表面轮廓仪、电子能谱仪(EDX)分别对涂层的磨损形貌、磨痕轮廓、磨损表面和磨屑的成分进行微观分析,对两种涂层转动微动损伤特征进行了讨论,得到以下结论：1.转动微动参数对CrN和AlCrN涂层的界面摩擦状态具有重要影响,两种涂层的转动微动运行区域依赖于法向载荷和转角位移幅值,随着法向载荷的降低或转角位移幅值的增加,涂层转动微动从部分滑移向完全滑移转变,相同工况下AlCrN涂层较CrN涂层更容易趋于部分滑移状态。2.CrN和AlCrN涂层的摩擦系数演变趋势极大地取决于所对应的微动状态,涂层在完全滑移状态下的摩擦系数较部分滑移的高,两种涂层摩擦系数值随法向载荷的增大而降低,随转动角位移幅值增大而增大,摩擦系数爬升阶段对应的循环次数随着法向载荷的增大而明显增加,但随转动角位移幅值增大而减少。在高载荷(Fn=40N)时,不同转角位移幅值下CrN涂层的摩擦系数稳定值都明显较AlCrN涂层的低。AlCrN涂层摩擦系数随着转角位移幅值的增大而明显增大,且曲线走势存在明显差异,而转角位移幅值的变化对CrN涂层的摩擦系数值影响不大。3.两种涂层在摩擦界面为部分滑移状态时,摩擦界面损伤较为轻微,产生的磨屑很少,而在完全滑移状态时,转动磨损损伤是二体作用和三体作用共同作用的结果,角位移幅值的增大涂层进入完全滑移状态后的损伤明显加重,产生较多的磨屑并分布在磨痕两端。高法向载荷(Fn=40N)下,转角位移幅值对两种涂层的转动微动损伤行为有重要影响,转动角位移幅值由1°增大为2°后,两种涂层在磨痕中心处的磨损特征以及排屑行为都存在明显的差异,主要为CrN涂层磨痕内有较明显的磨屑碾压堆积,而AlCrN涂层具有较好的排屑行为,磨痕中心处有明显的塑性累积隆起的痕迹。完全滑移状态下两种涂层的损伤随转角位移幅值的增大而明显加重,但磨损机理都主要为磨粒磨损和轻微的氧化磨损。更多还原

【Abstract】 CrN and ternary Cr-Al-N coatings deposited by Physical Vapor Deposition (PVD) technique have been successfully used to the surfaces of tools, dies, bearings, piston rings and other wear-resistant parts for their excellent integrated properties. Particularly, the AlCrN coating with high content of Al had excellent performance in high temperature oxidation resistance and good abrasive wear resistance, and thus had become the most promising PVD ternary nitride coating for wear and corrosion protection. Rotational fretting wear is caused between the contact pairs under alternating load with relative rotate motion. It widely exists in industrial equipments, civil mechanical and medical devices, which usually cause accidents and thus incalculable loss. The coating materials can be used for fretting wear and fatigue protection, CrN and AlCrN coatings have shown great potential in rotational fretting wear protection, which had highly increased the great anti-wear resistance of high-end main bearings and ball valves. However, so far there are few reports on the rotational fretting wear properties of these two coatings.In this paper, the rotational fretting behaviors of CrN and AlCrN coatings were studied under different normal loads (Fn=10 N,20 N,40 N) and rotating angular displacement amplitudes (θ=0.25°,0.5°,1°,2°) by using a new developed rotational fretting wear tester with a contact configuration of ball-on-flat. The Si3N4ball was used as counterpart materials. The wear scars were evaluated using scanning electron microscope (SEM), surface profiler, energy dispersive x-ray spectroscopy (EDX), and the rotational fretting wear mechanisms of the two coatings were discussed in detail. The main conclusions are drawn as follows:1. Rotational fretting parameters have important influence on interface friction state of both the CrN and AlCrN coatings. Their rotational fretting region of the coatings greatly depends on normal load and rotating angular displacement amplitude. When normal load decreases and angular displacement amplitude increases, rotational fretting running state of the coatings transfers from the partial slip to the gross slip. In the same condition, AlCrN coating was more prone to run on the partial slip as compared with CrN coating.2. The variation of the friction coefficients of the CrN and AlCrN coatings are greatly depend on the slip status. The friction coefficients of the two coatings under the condition of gross slip are higher than those under the partial slip. The friction coefficients of the coatings increase with the decrease of the normal load or the increase of displacement amplitude. The number of cycles corresponding to the ascent state significantly increases with increasing normal load, but decreases with increasing angular displacement. Under the high normal load of 40 N, the steady friction coefficient values of CrN coating are obviously lower than those of AlCrN coating at different angular displacement amplitudes. As the angular displacement amplitude increases, higher value with quite different curve trends has been observed for the friction coefficients of AlCrN coating, while no visible change for the friction coefficients of CrN coating.3. When friction contact interface of the two coating is running in the regime of partial slip, the coatings exhibit slight wear with little amount of wear debris. When running in the gross slip, the wear of the coating is two-body wear combining with three-body wear. Transferring to the gross slip by increasing the angular displacement amplitude will lead to heavier wear with more debris accumulation at the edges of the wear scar. Under the high normal load of 40 N, the angular displacement amplitude has significant influence on the wear properties of the two coatings. With the angular displacement amplitude increasing from 1°to 2°, the two coatings exhibit difference in wear characteristics and wear debris removal behavior at the center of the wear scar:compaction and accumulation of wear debris is observed inside the wear scar of CrN coating, while a relative higher efficient of wear debris removal besides a plastic deformation accumulation in middle of the wear scar is found for the AlCrN coating. The increase of angular displacement amplitude in the gross slip significantly aggravate the wear of the two coatings, though the wear mechanisms of the coatings are mainly abrasive wear and mild oxidative wear.更多还原