【作者】 肖茂华；

【导师】 何宁；

【作者基本信息】 南京航空航天大学 ， 机械制造及其自动化， 2010， 博士

【摘要】 镍基高温合金具有较高的高温强度、塑性、耐腐蚀性和良好的工艺性,广泛地应用于制造航空发动机、各类燃气轮机热端部件;同时它也是最难加工的材料之一,加工时切削温度高,加工硬化严重,刀具磨损严重,生产效率低。为实现镍基高温合金的高速高效切削,本文在国家科技支撑计划(2008BAF32B09)等项目的资助下,以镍基高温合金的高速切削过程为主要研究对象,以刀具磨损机理研究为主线,采用理论分析、数值模拟和加工试验相结合的方法,重点研究了影响刀具磨损的诸多因素和切削机理。主要研究工作如下:1、以传热理论和能量法为基础,设计了基于量热法和温度补偿技术的高速铣削切削热试验方法。该方法辅以热量损失补偿技术,精确计算了高速铣削时的切削热及其分配。基于该方法,研究了陶瓷刀具高速切削镍基高温合金时的切削温度、切削热及其分配,并分析了切削速度、刀具磨损等对切削功率、切削温度、切削热量分配等的影响。研究分析了镍基高温合金切削热分配与碳钢切削热分配的差异,及其对切削温度和刀具磨损的影响。通过有限元仿真模拟了二维正交切削的温度场分布,通过解析法计算出了切削热在切屑、刀具和工件的分配,并与试验结果进行了对比。2、研究了硬质合金刀具、陶瓷刀具、PCBN刀具等在不同条件下高速切削镍基高温合金时的刀具耐用度和刀具磨损情况,分析了刀具材料、切削条件、工件材料等对刀具耐用度的影响,并通过扫描电镜、能谱仪等对刀具的磨损形态进行了观测与分析,探讨高速切削镍基高温合金时刀具的磨损机理,并提出了基于切削力的刀具磨损监测方法。3、基于对高速切削镍基高温合金时的切屑形貌和切屑变形机理分析,研究切屑毛边冲击对刀具沟槽磨损产生的影响。建立了切屑毛边对刀具沟槽磨损部位的冲击模型,测量了沟槽磨损的实际位置,计算了切屑毛边的冲击压强和冲击频率,揭示了刀具的沟槽磨损机理主要是由切屑毛边和切削毛刺的冲击造成的。4、通过陶瓷材料的冲击疲劳特性和切削毛刺、切屑毛边对刀具沟槽磨损部位的冲击分析,建立了锯齿状切屑毛边和侧向切削毛刺高速高温高频连续冲击的沟槽磨损模型。基于该模型,提出沟槽磨损的主要原因是由于侧向切削毛刺和锯齿状切屑毛边的冲击作用所造成的刀具疲劳损伤。同时,通过切削毛刺单独冲击试验,验证了切削毛刺的连续冲击可以产生沟槽磨损。通过自行设计的去毛刺试验台,进行了去毛刺切削试验,验证了沟槽磨损模型的正确性,并提出了在切削加工中抑制沟槽磨损的方法。更多还原

【Abstract】 Nickel-based superalloy is widely used as aircraft engine parts, chemical processing, pressure vessels, steam turbine power plants etc. Its properties such as creep and corrosion resistance, as well as the abilities to maintain high strength-to-weight ratio, are vital for the economic exploitation of aerospace engines. But due to peculiar characteristics such as lower thermal conductivity,work hardening, presence of abrasive carbide particles,hardness, affinity to react with tool material etc makes it difficult to machine. In order to realize high speed and high efficient cutting of nickel-based superalloy, the tool wear mechanism on the cutting process is studied emphasizedly. Theoretical analysis, numerical simulation and experimental verification are applied in this research. The major research works are included as follows:1.Based on heat transfer theory and energy method, calorimetric method and temperature compensation were designed based on high-speed milling cutting heat test. The temperature variations of the water and the surroundings during the closed high-speed milling were then measured, and the cutting heat in the chip was calculated and compensated. The cutting temperature, cutting heat, cutting heat in the chip were calculated, and the effect of cutting speed,feed rate and tool wear on the power of chip and the cutting force,cutting heat distribution and the cutting temperature etc were studied. The cutting heat distribution of nickel-based superalloy was compared to carbon steel. The temperature distribution of in orthogonal cutting was simulated by FEM simulation. Based on the FEM simulation and the analytical method, the heat distribution in chip,workpiece and tool in different cutting speeds was investigated. The result of FEM simulation and analytical method accorded with the experimental results.2. The tool life and tool wear mechanism of carbide tools, ceramic tools and PCBN during high speed cutting nickel-based superalloy were studied. The effect of tool material, cutting conditions, workpiece material etc on tool life were investigated, and the empirical formula of tool life on high speed turning and milling GH4169 were established. The tool wear morphology and wear mechanism were studied by SEM, EDS and x-ray diffraction analysis on the tool rake face, flank face,chip and notch wear location. A method was proposed to monitor tool wear based on the cutting force.3.The chip morphology and chip deformation mechanism of high speed cutting nickel-based superalloy were studied. A cantilever chip edge shock model was established to calculate the impact force, impact pressure and impact frequency of chip edge on tool edge. Their effect on notch wear formation was studied. The measurement of the actual position of notch wear proved that only serrated chip edge and cutting burr can effect the notch wear position.4. Based on the above analysis and experimental basis, the impact fatigue characteristics of ceramic materials was analyzed and the temperature pulse calculation in the notch wear location was calculated. On the basis of theoretical analyses and calculations of high speed continuous impact force and tool notch surface temperature acted upon by burr and serrated chip edge, a notch wear model of low stress value and temperature impact fatigue was established. Saw-tooth-shaped burr and fin-shaped chip edge continuously impact the flank face and rake face at high speed and high frequency, which results in a V-shaped notch wear. The role of bonding is to change the direction of the impact stress, and accelerate the micro-crack initiating and propagating. The impact test of separate cutting burr was carried to investigate whether side cutting burr could create notch. A new cutting test-bed was devised to deburr and a lot of experiments were done in deburring cutting and normal cutting. The results of the experiments proved the correctness of the notch wear model. The method to suppress notch wear was proposed too.更多还原