【作者】 刘鹏；

【导师】 徐九华；

【作者基本信息】 南京航空航天大学 ， 机械制造及其自动化， 2011， 博士

【摘要】 钛合金具有比强度高、热强度高、抗断裂性高、耐腐蚀性好等优良特性，在航空航天、化工、船舶和核技术等领域得到了广泛的应用。钛合金同时具有导热系数小，高温化学活性高，弹性模量低，摩擦系数大等特性，易导致其加工性能差。目前国内外钛合金加工主要采用硬质合金刀具，切削速度一般在60m/min左右，大大限制了钛合金的加工效率，如何实现对钛合金材料进行高效精密加工成为一个亟待解决的难题。聚晶金刚石刀具（Polyerystalline Diamond，简称PCD）可以实现对钛合金的高效精密加工，与硬质合金刀具相比具有切削速度高、刀具耐用度长等优势。本文针对TA15钛合金材料，开展了超硬刀具高速铣削钛合金的基础研究，主要研究工作包括以下方面：1.高速铣削钛合金的超硬刀具设计。结合钛合金的高速切削加工特点和超硬刀具高速铣削钛合金的试验，设计出适用于钛合金高速铣削的PCD刀具，有效的控制了高速断续切削中超硬刀具的崩刃。利用有限元分析技术，模拟了PCD刀具高速切削TA15钛合金时切削刃上的接触应力场，分析了刀具的几何参数对刀具破损的影响，验证了刀具参数设计的合理性。2.超硬刀具高速铣削钛合金切屑形态研究。通过高速铣削TA15钛合金试验，对比研究不同刀具材料、不同切削用量以及不同刀具磨损状态对切屑宏观和微观形貌的影响及其原因。借助金相试样显微分析方法，研究刀具材料、切削用量和刀具磨损对切屑变形的影响，寻找锯齿化程度、集中剪切频率、剪切角和滑移角随切削用量的变化规律。3.超硬刀具高速铣削钛合金刀具耐用度研究。通过利用三维视频显微镜、扫描电镜和能谱分析等手段，对不同切削速度下的刀具磨损状态进行跟踪测量，对比研究了高速精加工TA15钛合金时PCD和硬质合金刀具的耐用度及其影响因素，观察和研究PCD和硬质合金刀具高速铣削钛合金时的刀具磨损形貌，为进一步阐述刀具的磨损机理奠定基础。4.超硬刀具高速铣削钛合金刀具磨损机理研究。首先从刀具—工件摩擦副的摩擦学特性入手，搭建了模拟高速切削过程的摩擦磨损试验平台，开展了高速滑动摩擦磨损试验，采用单点和双点快速热电偶标定法，对所使用的自然热电偶进行了标定。定量对比分析了PCD和硬质合金与TA15钛合金摩擦副之间的摩擦磨损特性，深入分析了速度和载荷对两种摩擦副的摩擦系数、摩擦温度以及摩擦磨损形貌的影响，借助扫描电镜和能谱分析手段，对摩擦磨损机理进行了探讨，在此基础上探讨了高速铣削TA15钛合金时PCD刀具的磨损机理。5.超硬刀具高速铣削钛合金表面完整性的研究。借助三维视频显微镜、显微硬度仪和表面粗糙度仪等仪器，研究了铣削用量、刀具磨损对表面完整性的影响规律。建立了表面粗糙度的理论模型和预测模型。研究了铣削用量和刀具磨损对加工硬化和表层显微组织的影响。利用有限元分析和试验相结合的方法，研究了切削速度对表层残余应力的影响，分析了残余应力的形成机理。更多还原

【Abstract】 Titanium alloys are widely used in aerospace, shipbuilding chemical, and nuclear because of theirhigh specific strength, good corrosion resistance and high thermal stability. However, titanium alloy iswell known as a difficult to machine material, because of its low thermal conductivity, small elasticmodule, and high chemical activity. Nowadays, both in home and abroad, titanium alloys aremachined with carbide cutting tools, and the cutting speed is about60m/min. So it is crucial toenhance the machining efficiency level. Compared with uncoated carbide cutting tools, thepolycrystalline diamond （PCD） cutting tools can have higher cutting speed and longer tool life. Thefundamental research on high speed milling of titanium alloys with super-hard tools has been carriedout. The major research works are included as follows:1. Parameter design of super-hard tools in high speed milling titanium alloy. According to thefeatures of titanium alloy and high speed milling experiments, a PCD tool was designed reasonablyfor high speed milling titanium alloy. Chipping of super-hard tool was effectively controlled inhigh-speed intermittent cutting. The contact stress field on cutting edge in high-speed cutting titaniumalloy with PCD tool was simulated. The effect of tool geometric parameters on the tool breakage wasanalyzed. It verified that the design tool parameters were reasonable.2. Study on chip formation mechanism in high speed milling of titanium alloy with Super-hard tool.The process of chip formation, chip shape and chip deformation were studied from both theoreticaland experimental aspects. Finite element analysis was used to simulate the process of chip formationin high-speed cutting titanium alloy with PCD tool. The effects of tool materials, cutting parametersand tool wear on macro and micro morphology of the chip were analyzed. By means of microanalysisof metallographic sample, effects of cutting parameters and tool wear on chip deformation werestudied. Variation of the saw tooth level, concentrated shear rate, shear angle and slip angle with thecutting parameters were studied comparatively with different tool materials.3. Tool life in high speed milling of titanium alloy with super-hard tool. The three-dimensionalvideo microscope, SEM and EDS were utilized to investigate the effect of cutting speed on tool wearof the titanium alloy. Tool life and tool wear morphology of PCD and carbide cutting tools werestudied comparatively in high-speed finishing milling titanium alloys. It would be helpful forrevealing the tool wear mechanism.4. Tool wear mechanism in high speed milling of titanium alloy with super-hard tool. Firstly, thefriction and wear behavior of super-hard tool sliding against TA15alloy were investigated at high sliding speeds. The test platform was established to simulate high speed cutting process. The frictiontests between cutting tool and TA15were carried out. A single point and double point thermocouplecalibration method were used to calibrate the natural thermocouple used in the experiments. The basictribological properties and friction parameters of carbide-TA15friction pair and PCD-TA15frictionpair were measured and analyzed. The friction wear mechanism was revealed deeply. The SEM andEDS were utilized to reveal the super-hard tool wear mechanism.5. Surface integrity in high speed cutting of titanium alloy with super-hard tool. By means ofthree-dimensional video microscope, micro hardness tester and surface roughness and otherequipments, effects of the milling parameters and tool wear on surface integrity are investigated. Atheoretical model and prediction model of surface roughness were established. Effects of the millingparameters and tool wear on work hardening and microstructure were studied. Finite element analysisand experimental methods were used to study the effect of cutting speed on residual stress, and theformation mechanism of residual stress was analyzed.更多还原