【作者】 马兴伟；

【导师】 金洙吉；

【作者基本信息】 大连理工大学 ， 机械制造及其自动化， 2011， 博士

【摘要】 人造金刚石膜,尤其是大尺寸的化学气相沉积(CVD)金刚石厚膜的制备技术日益成熟,其应用范围从传统的刀具、模具等领域不断向高频通讯、光电等高新技术领域扩展,对其加工精度和表面质量的要求也日益提高。然而,由于金刚石具有高硬度、高化学惰性等特点,属极难加工材料,虽然目前已有多种金刚石膜的抛光技术,但是这些技术仍难以满足高效低成本抛光要求,相对滞后的金刚石膜抛光技术越来越成为限制金刚石膜广泛应用的障碍。高速摩擦抛光技术是在大气环境下借助抛光盘与金刚石膜之间的高速摩擦作用使加工区域局部达到金刚石石墨化转变所需的温度(通常为600-800℃),并利用加工区域的摩擦-热化学复合作用实现快速抛光的一种新型金刚石膜抛光技术。该技术不需要真空或者密闭性气氛,也不需要加热设备,甚至不需要昂贵的专用抛光设备,是一种非常有发展前途的金刚石膜高效低成本抛光技术。但为了保证抛光盘对金刚石具有很强的石墨化催化能力,目前该技术中使用的抛光盘大多由不锈钢或铸铁等含铁材料制成,由于这些材料在高温下强度和硬度较低,因此在高速、高压及高摩擦温度的条件下采用这些材料制成的抛光盘对极高硬度的粗糙金刚石膜进行高速摩擦抛光时,抛光盘塑性变形和磨损极为严重,甚至会出现抛光盘材料向金刚石膜表面的严重黏附,不仅严重影响了抛光盘的面型精度,而且导致金刚石膜抛光效率和抛光质量的降低。因此,亟待研究和开发一种兼备高温耐磨性和对金刚石石墨化催化能力的新型抛光盘材料。另外,在对极高硬度的金刚石膜抛光时,必须使金刚石膜被加工区域局部达到石墨化转变温度并借助摩擦-热化学复合作用才能实现金刚石膜粗糙表面的高效抛光,但温度过高时会导致抛光盘的硬度、耐磨性等急剧下降,影响金刚石膜的抛光效率,而且温度过高时还有可能导致金刚石膜的严重石墨化和整体氧化,使金刚石膜性能降低甚至报废。因此,预测并控制加工区域的温度,是实现高效高精度抛光的关键环节。但由于采用高速摩擦抛光技术时加工区域的温度场受抛光盘转速、抛光压力以及整个抛光工艺系统的热传导属性等多种因素的耦合作用影响,加工区域的温度场分布难以预测。本文针对金刚石膜高速摩擦抛光技术中存在的上述问题,采用高能球磨和热压烧结相结合的技术研制开发了一种新型的抛光盘材料——FeAl基合金,并通过掺杂稀土优化了该抛光盘材料的性能；采用ANSYS仿真软件对金刚石膜高速摩擦抛光过程中金刚石膜的温度场进行了仿真,得出了适合金刚石膜高速摩擦抛光的理想抛光工艺参数；最后分别采用不锈钢304(文中简记为SS304)抛光盘及自制的FeAl基合金抛光盘对金刚石膜进行高速摩擦抛光,对比研究了两种抛光盘对金刚石膜的抛光效果,并分析了FeAl基合金抛光盘高速摩擦抛光金刚石膜时的抛光过程和机理。主要研究内容包括：(1)根据高速摩擦抛光技术的抛光原理和技术特征,选择具有反温度-强度特征、耐磨性能优异以及对金刚石具有石墨化催化作用的FeAl基合金作为抛光盘材料,并采用高能球磨和热压烧结技术制备了掺杂不同含量稀土的FeAl基合金。分析了球磨时间和稀土含量对FeAl基合金组织结构、致密度、硬度、弯曲强度、抗氧化性能以及高温耐磨性能的影响。结果表明：含1wt.%稀土的Fe、Al混合粉末经60h高能球磨及1200℃×30MPa×1h真空热压烧结制备的FeAl基合金具有最佳的综合性能。(2)采用自制的FeAl基合金抛光盘,在空气中采用不同的试验温度(550-800℃)对金刚石膜进行热化学抛光,研究了温度对FeAl基合金抛光盘磨损状况和金刚石膜抛光效果的影响。结果表明：FeAl基合金抛光盘在大气中抛光金刚石膜时,理想的抛光温度范围是650-700℃。(3)基于对金刚石膜抛光前后表面形貌的分析,建立了一种金刚石膜表面微凸体的四棱台结构几何模型,在此基础上利用ANSYS热分析软件对金刚石膜高速摩擦抛光过程中的摩擦温度场进行了仿真。通过仿真,确定了采用FeAl基合金抛光盘对金刚石膜进行高速摩擦抛光时的理想工艺参数：抛光压力80N(5MPa)、抛光盘转速1440r/min (10.25m/s).(4)分别采用SS304抛光盘和自制的FeAl基合金抛光盘对金刚石膜进行高速摩擦抛光,对比研究了两种抛光盘对金刚石膜的抛光效果,并对FeAl基合金抛光盘高速摩擦抛光金刚石膜时的抛光过程和机理进行了分析。研究发现,采用FeAl基合金抛光盘时,金刚石膜的材料去除率为7.89mm3/h,比采用SS304抛光盘时提高68%；而从抛光盘的磨损率来看,FeAl基合金抛光盘的磨损率仅为SS304抛光盘磨损率的15%；抛光机理为：在摩擦热和铁触媒的共同作用下,金刚石膜表面的微凸峰发生石墨化转变,形成较软、易氧化并具有更强扩散能力的石墨相,石墨相在机械作用、氧化作用以及扩散作用的共同作用下被去除。更多还原

【Abstract】 The preparation technique of man-made diamond film especially the large size chemical vapor deposition (CVD) thick diamond film has greatly developed these years. Diamond film has been applied from the tranditional areas of cutter and mould to the high-tech fields such as high frequency communication and photoelectricity, so the standards of processing accurity and surface quality requires much higher. However, diamond film is very difficult to process since its characteristics of high hardness and high chemical inertness. Although there have already been some kinds of diamond film polishing techniques, they can not meet the requiments of high efficiency and low cost. Relatively lagged diamond film polishing techniques are becoming the main barriers for the wide spread applicatin of diamond film.Dynamic friction polishing is a new polishing technique which can realize fast polish by the complex friction-thermochemistry effect in processing area. It enables the processing area to achieve the transition temperature (usually 600-800℃) of diamond to graphite in atmosphere, by the high-speed friction effect between polishing plate and diamond film. This polishing technique is very promising because it neither requires vacuum or sealed atmosphere nor needs heating equipment, not even needs the expensive polishing equipment. Materials containing iron element such as stainless steel or cast iron are normally used to make polishing plate in order to ensure polishing plate’s strong catalytic ability on diamond, however, these materials can hardly adapt to polishing environment such as high temperature and high-speed friction. In that case, the polishing plate is easily worn out which seriously affect the polishing precision, what’s worse is that polishing plate gets sharp plastic deformation and the deformed material adheres to the diamond surface, which leads to the drop of the polishing efficience and polishing quality. Therefore, it is urgent to develop a new type of polishing plate material with the quality of high-temperature wear resistance and strong catalytic graphitization ability on diamond. In addition, efficient removal can only be realize with the processing area achieving the transition temperature of diamond to graphite, and with the help of the composite action of friction-thermochemistry during the diamond film processing. However, if the temperature is too high, it would lead to the sharp decline of polishing plate’s hardness and wear resistance, which results in low processing efficiency and precision, what’s worse is that the too high temperature even leads to the extreme graphitization and overall oxidation. In that case, calculation and control of temperatures field in the processing area are key for efficient and high-precision processing, however, the calculation of the temperature field during the dynamic friction polishing is extremely difficult because it can be affected by combined effects of many factors such as polishing rotation rate, polishing pressure, and polishing system’s thermal conductivity.A new type of polishing plate material—FeAl based alloy, was developed by the technology of combining high-energy ball-milling and hot-pressing sintering, aiming at solving the problems of existing in dynamic friction polishing techniques mentioned above, and the performances of the polishing plate material were optimised by doping rare earths. Diamond film’s temperature field during dynamic friction polishing process was simulatd with the help of ANSYS simulation software, and the reasonable parameters for diamond films dynamic friction polishing was obtained based on the simulation. Diamond films were polished by dynamic friction method with stainless steel 304 (abbreviated as SS304) polishing plate and self-made FeAl-based alloy polishing plate respectively, and the polishing effect of these two kinds of polishing plates was compared. Dynamic frictional polishing process and mechanism using FeAl based alloy polishing plate were also analyzed. The main research contents include:(1) According to the principles and characteristics of the dynamic friction polishing technology, we chose FeAl based alloy which has the quality of abnormal temperature-strength, excellent wear resistance and catalytic graphitization ability on diamond as polishing plate material. We further prepared sintered FeAl based alloys with different content of rare earth using high-energy ball milling and hot-press sintering technique, and analyzed the effect of milling time and rare earth content on the sintered alloy’s structure, density, hardness, flexural strength, oxidation resistance and high temperature wear resistance. The results showed that the FeAl based alloy which is made of Fe and Al mixed powder doped 1wt.% rare earth, ball-milled for 60 hours and sintered for 1 hour in Vacuum at 1200℃under the stress of 30MPa has the best combination property.(2) Diamond film was polished by using the self-made FeAl based alloy plate under different temperature at the atmosphere, and the influence of polishing temperature on the wear situation of FeAl based alloys as well as the polishing effect on diamond film was also analyzed. The results showed that the ideal temperature range for FeAl based alloys polishing diamond film is 650～700℃.(3) A quadrangular frustum pyramid model of the diamond asperity was built based on the diamond film surface topography before and after polishing, and the temperature field of diamond film during the dynamic friction polishing was simulated with the help of ANSYS thermal analysis software. Based on the simulation, we concluded that the best parameters of FeAl based alloy plate polishing diamond film are as follows:polishing pressure 80N (5MPa), polishing speed 1440r/min (10.25m/s).(4) We compared the polishing effects of two kind of polishing plates, one of which is made of SS304 and the other is made of our self-made FeAl based alloy, by doing dynamic friction polishing on diamond film. The polishing mechanism of using FeAl alloy polishing plate was also analyzed. The results showed that with FeAl alloy as the material the removal rate of diamond film can be 7.89mm3/h which is 68% higher than that with SS304, the wear rate of FeAl alloy polishing plate is only 15% of that of SS304. The polishing mechanism is: under the combined action of friction heat and iron catalyst, a soft, easily oxidized and fast diffusible graphite phase formed on the asperities of diamond film by the graphite transition, then the graphic phase was removed under the combined action of mechanical action, oxidation and diffusion.更多还原