【作者】 肖正涛；

【导师】 王佳；

【作者基本信息】 中国海洋大学 ， 应用化学， 2011， 硕士

【摘要】 冷喷涂技术是一种新兴的表面工程技术,其利用气流加速粒子使之以固态高速撞击基体表面形成涂层。在喷涂过程中,由于其喷涂温度低、无相变及氧化现象,形成的涂层致密,孔隙率低等优点而被广泛关注。本论文的主要研究内容是利用X射线衍射技术（ XRD ）、扫描电镜及EDS能谱分析、显微硬度、结合强度、耐磨性及耐腐蚀性试验等手段对利用冷喷涂工艺制备的冷喷涂铜涂层、冷喷涂Cu-20wt%Al₂O₃复合涂层、冷喷涂Cu-20wt%SiC复合涂层和冷喷涂Cu-50wt%SiC复合涂层四种涂层物理及电化学性能进行研究。此外,本文还研究了热处理对四种冷喷涂涂层微观组织结构、显微硬度、耐磨性的影响。研究结果显示:冷喷涂制得的铜涂层与基体结合致密、分界面不明显,孔隙率较低;冷喷涂过程中铜粉末颗粒未发生明显的氧化现象;涂层显微硬度较高;厚度对冷喷涂铜涂层的结合强度及摩擦性能影响较小。经动电位极化曲线和电化学阻抗谱测试表明,随着浸泡时间的延长,冷喷涂铜涂层腐蚀电流密度很小,极化电阻较大,涂层的耐蚀性能较好。经退火热处理后,冷喷涂铜涂层性能发生了明显的变化:在一定热处理温度范围内（500℃以下）,随热处理温度的升高,冷喷涂涂层结合强度大大增加,由喷涂态的6MPa提高到45MPa左右,但显微硬度却成明显的下降趋势:由未处理前132.94Hv0.2降低至41.8Hv0.2（HT500℃）。300℃热处理温度下,冷喷涂涂层主要以去应力退火为主,涂层宏观结构变化不明显,涂层显微硬度明显下降,涂层结合强度增大;500℃热处理温度下,涂层发生了再结晶现象,涂层显微硬度继续呈下降的趋势,但涂层结合强度达到最大值44.6MPa;当退火温度达到700℃时,涂层的显微硬度降至最低值,涂层结合强度有所下降。为了增加冷喷涂铜的显微硬度,提高涂层的耐磨性加入不同比例的Al2O3、SiC硬质颗粒。本文成功制备的三种复合涂层结构致密,硬质粉末均衡地分布在涂层中,在喷涂过程中硬质粉末未发生明显的分离;涂层的显微硬度都明显得到提高;三种冷喷涂态复合涂层在摩擦过程中均出现了硬质粉末脱离的现象,在摩擦过程中,硬质粉末的脱离使摩擦进入三体系摩擦系统,涂层主要以磨粒磨损为主。三种复合涂层经不同温度退火热处理后,涂层结构发生明显的变化。与冷喷涂铜涂层一样,在300℃退火温度下,复合涂层均表现出了以去应力退火为主的结构变化,并且显微硬度呈一定程度的下降;在500℃退火温度下,涂层中出现了再结晶现象,涂层颗粒增大,涂层结合更加致密,涂层硬度下降明显;700℃退火温度下,涂层再结晶现象明显,涂层颗粒进一步增大,涂层显微硬度降低。在耐磨性试验中,三种退火态复合涂层的磨损机制各不相同: Cu-20wt%Al₂O₃复合涂层,在喷涂态和低退火温度（300℃和500℃）时,涂层硬度较高,在磨损过程中,涂层的磨损以Al₂O₃颗粒的磨粒磨损为主;当退火温度达到700℃时,涂层显微硬度明显下降,涂层出现剥离、脱落现象,涂层的磨损机制主要为磨粒磨损和粘着磨损。Cu-20wt%SiC复合涂层喷涂态和300℃热处理温度下,磨痕处明显有沟槽状犁削划痕存在,涂层的磨损主要为磨粒磨损;当退火温度升高（500℃和700℃）时,涂层硬度降低,涂层在摩擦副的作用下出现脱落,涂层的磨损机制以磨粒磨损和疲劳磨损为主。随着SiC含量的升高,Cu-50wt%SiC复合涂层在300℃、500℃和700℃时,涂层均出现了明显的剥离、脱落现象,均表现出了明显的颗粒的磨损和疲劳磨损,涂层耐磨性能明显降低。更多还原

【Abstract】 Cold gas dynamic spraying （CGDS） process is a new surface engineering technology. In the spraying process, the coating is deposited through plastic deformation of metallic spray particles in a completely solid state with high velocity impact. It has attracted serious concern for its advantages: low spraying temperature, absence of phase transition and oxidation, low porosity level, dense microstructure, good adherence to the substrate, and so on.In this paper, the characters of cold-sprayed copper coating, cold-sprayed Cu-20wt%Al₂O₃ composite coating, cold-sprayed Cu-20wt%SiC composite coating, and cold-sprayed Cu-50wt%SiC composite coating were studied through XRD analysis, SEM, micro-hardness, combination test, wear resistance test and anticorrosion experiment. Furthermore, the effect of vacuum heat treatment on the microstructure, micro-hardness and wear-resistance of the four kinds of coatings are investigated.Studies showed: as-deposited coatings presented the dense microstructure, low porosity; little or no oxidation phenomenon. Thickness of the coatings has no obvious effect on the combination strength and tribological property. By potentiodynamic polarization curves tests and EIS tests, the cold-sprayed copper coating showed good corrosion resistance and the corrosion rate of coatings retained a low level with immersion time.After heat treatment, the cold-sprayed copper coatings present a far different property from that of the as-sprayed coatings. In a certain range of heat treatment temperature （500℃or less）, the bonding strength of the coatings significantly increased with the heat treatment temperatures increasing: from the cold-sprayed 6MPa to about 45MPa after heat treatment, but the micro-hardness decreased obviously: from 132.94Hv0.2 cold-sprayed to 41.8Hv0.2（HT500℃）. At annealing temperature of 300℃, stress relief annealing plays an important role in the cold-sprayed copper coating, and there is no evident macrostructure change. At this annealing temperature, the micro-hardness decreased evidently, and the combination strength increased. Apparent recrystallization can be seen clearly at 500℃, and the combination strength reaches the maximum 44.6MPa. The micro-hardness decreased with the growth of the annealing temperature.The mental/ceramic coatings were successfully prepared by CGDS. In the composite coatings, the structure is denser, the Al₂O₃ and SiC reinforce particles balancing spread in the coating, and the micro-hardness of the composite coatings increased evidently. For the as-sprayed composite coatings, such factors as ploughing and abrasive wear could determine the sliding process.After heat treatment, the composite coatings present far different properties from that of the as-sprayed composite coatings. At annealing temperature of 300℃, stress relief annealing takes an important role in the cold-sprayed composite coatings, and the micro-hardness decreased evidently. Apparent recrystallization and grain growth occurred at 500℃. When the annealing temperature was 700℃, the recrystallization was evident, and the micro-hardness reach the minimum.In the wear-resistance tests, the tribological mechanisms of the three kinds of composite coatings are different. For the cold-sprayed Cu-20wt%Al2O3 composite coating, the abrasive wear takes an important role in the sliding process to the as-sprayed composite coating and the low temperature （300℃and 500℃） annealed composite coatings. At the annealing temperature of 700℃, such factors as abrasive wear and adhesion wear play a dominant role. In the wear resistance tests of as-sprayed Cu-20wt%SiC composite coating and HT300℃Cu-20wt%SiC composite coating, the abrasive wear is the dominant wear type. At the annealing temperature of 500℃and 700℃, the abrasive wear and adhesion wear play an important role in the sliding process. With the content of the reinforce particle of SiC increasing, such factors as abrasive wear and fatigue wear play a dominant place in the as-sprayed composite coating and all the annealed composite coatings.更多还原