【作者】 殷增斌；

【导师】 黄传真；

【作者基本信息】 山东大学 ， 机械制造及其自动化， 2014， 博士

【摘要】 现阶段陶瓷刀具材料研制多采取“试凑法”的研究方式,本文针对研制过程存在的盲目性和实验量大的弊端,提出了复合陶瓷刀具材料的多尺度设计理论,揭示了复合材料宏观性能和其微观组织之间的定量关系；研制成功了多尺度颗粒复合陶瓷刀具材料,并对刀具材料的烧结工艺、微观组织、增韧补强机理、室温和高温力学性能、动态疲劳性能、切削性能和切削可靠性进行了系统研究。提出了复合陶瓷刀具材料的多尺度设计理论。建立了刀具材料抗弯强度预测模型、残余应力力学模型、纳米颗粒最优含量数学模型和金属相完全填充颗粒间隙时的最优含量数学模型。根据复合陶瓷刀具材料抗弯强度预测模型、刀具材料残余应力力学模型、纳米颗粒最优含量数学模型和金属相完全填充颗粒间隙的最优含量数学模型,设计了两种Al203基多尺度颗粒复合陶瓷刀具材料,其一是Al2O3μ-TiCμ-TiCn-Co,微米TiC、纳米TiC和金属Co的体积含量分别为35%、6%和3%；其二是Al2O3μ-(W,Ti)Cμ-TiCn-Ni/Co,微米(W,Ti)C、纳米TiC和金属Ni或Co的体积含量分别为33%、6%和4%。研究了纳米颗粒含量、金属相含量对A1203基多尺度颗粒复合陶瓷刀具材料室温力学性能和微观组织的影响。结果表明,当纳米TiC颗粒的含量为6vo1.%时,裂纹沿晶与穿晶扩展的比例适当,材料的抗弯强度和断裂韧度较好,验证了纳米颗粒最优含量数学模型的正确性；金属Co含量过少或过多时,材料力学性能均降低,其存在一最佳含量,从而验证了金属相最优含量数学模型的正确性。优化了陶瓷刀具材料的烧结工艺。Al2O3μ-TiCμ-TiCn-Co陶瓷刀具材料在烧结温度为1650℃、保温时间为20min和烧结压力为32MPa时获得最优的室温力学性能,其抗弯强度、断裂韧度和维氏硬度分别为8.3MPa·m1/2和18GPa。Al2O3μ-(W,Ti)Cμ-TiCn-Co陶瓷刀具材料在烧结温度为1650℃、保温时间为30min和烧结压力为32MPa时获得最优的室温力学性能,其抗弯强度、断裂韧度和维氏硬度分别为882MPa、7.2MPa-m1/2和19GPa。*本研究得到了高档数控机床与基础制造装备科技重大专项课题(2012ZX04003-051)资助。研究了A1203基多尺度颗粒复合陶瓷刀具材料的增韧补强机理。结果表明,微米增强颗粒的主要增韧补强机理是晶粒桥接和裂纹偏转；纳米增强颗粒的主要增韧补强机理是晶界钉扎、晶粒细化、裂纹二次偏转和穿晶断裂；金属相的主要增韧补强机理是基体中的残余拉应力降低和界面结合强度提高。研究了陶瓷刀具材料的高温力学性能和动态疲劳性能,揭示了陶瓷刀具材料高温力学性能和动态疲劳性能随温度变化的规律,建立了陶瓷刀具材料在高温时裂纹缓慢扩展机理模型,提出了陶瓷刀具材料高温抗弯强度、高温断裂韧度和动态疲劳性能的弱化机理。结果表明,Al2O3-TiCμ-TiCn-Co陶瓷刀具材料的抗弯强度随着温度的升高而降低,断裂韧度随温度的升高先降低,当温度达到1200℃时材料发生一定的塑性变形,此时断裂韧度升高。不含金属相的刀具材料的室温抗弯强度和高温抗弯强度差别较小；含金属相的刀具材料抗弯强度随温度升高而剧烈降低,金属相含量越高,刀具材料的高温抗弯强度降低幅度越大。该陶瓷刀具材料在室温和高温时均存在亚临界裂纹扩展行为；与室温相比,材料在高温时的抗疲劳性能显著降低；适量的金属相能提高陶瓷刀具材料在室温和高温时的抗疲劳性能。Al2O3-TiCμTiCn-Co陶瓷刀具材料高温抗弯强度的主要弱化机理是材料被氧化侵蚀,微观组织被破坏；高温时富金属相晶界变软,界面结合强度降低,裂纹倾向于沿晶扩展,并产生沿晶断裂；高温时材料的弹性模量降低；材料发生塑性变形,晶界移动产生晶界缺陷。该陶瓷刀具材料在室温和900℃高温时的疲劳失效机理是应力腐蚀裂纹,在1200℃高温时的疲劳失效机理主要是蠕变。研究了陶瓷刀具加工难加工材料时的切削性能和切削可靠性。创建了陶瓷刀具材料动态疲劳性能和陶瓷刀具疲劳破损寿命之间的关系模型,建立了陶瓷刀具磨损寿命分布模型和切削可靠度模型。研究了A1203基多尺度颗粒复合陶瓷刀具连续切削奥氏体不锈钢1Cr18Ni9Ti的切削性能和切削可靠性。结果表明,当v=80m/min,f=0.15mm/r,αp=0.1mm时,金属去除量最大,刀具寿命为13min。。刀具磨损寿命服从伽马分布。刀具可靠度为0.5时刀具磨损的可靠寿命约为9min;刀具可靠度为0.8～0.9时,刀具磨损的可靠寿命为5.5-6.5min。具有不同倒棱宽度和不同刀尖圆弧半径的四种刀具抗磨损能力由强到弱依次为ATTC(b=0.1mm, r=0.1mm)> ATTC(b=0.3mm,r0.3mm)=LT55>AWTC。刀具的主要失效形式是疲劳破损造成的切削刃脆断和后刀面材料剥落,其主要失效机理是磨粒磨损和粘结磨损。研究了A1203基多尺度颗粒复合陶瓷刀具连续湿式切削冷作模具钢Cr12MoV的切削性能和切削可靠性。结果表明,当v=60m/min,f=0.1mm/r, ap=0.1mm时,工件加工表面的粗糙度最小,刀具磨损寿命为9min。ATTC(b=0.3mm, r=0.3mm)刀具磨损寿命服从对数正态分布。刀具可靠度为0.5时,刀具磨损的可靠寿命约为7.5min；刀具可靠度为0.8～0.9时,刀具磨损的可靠寿命为4.5～5.3min。具有不同刀尖圆弧半径的ATTC刀具在干式切削和湿式切削Cr12MoV时,表面粗糙度由小到大依次是(湿式切肖(?),b=0.3mm, r=0.3mm)<(干式切削,b=0.1mm, r=0.1mm)<(湿式切削,b=0.1mm, r=0.1mm)<(干式切削,b=0.3mm, r=0.3mm)。在湿式切削时,刀具的主要失效形式是沟槽磨损、边界磨损、后刀面材料剥落和主切削刃微崩,其主要磨损机理是磨粒磨损和粘结磨损。更多还原

【Abstract】 In order to solve the problems of great blindness and large amount of experiments brought from the trial and error method for developing ceramic tool matarials, the multi-scale design theory of ceramic tool materials was established. The theory revealed the quantitative microstructure-property relationship of composite ceramic tool materials. Two kinds of ceramic tool materials were designed and fabricated under the guidance of the proposed design theory. Their sintering technology, microstructure, strengthening and toughening mechanisms, room and high temperature mechanical properties, dynamic fatigue behavior, cutting performance and cutting reliability were deeply investigated.The multi-scale design theory of composite ceramic tool materials was proposed and established. Based on the studies on the physical and mechanical process of microstructure and the distribution of liquid phase in ceramics, the flexural strength prediction model of composite ceramic tool materials, the residual stresses mechanics model, the mathematical model of the optimal content of nano-scale particles and the mathematical model of the optimal content of the metallic phase were built.Two kinds of multi-scale particles reinforced alumina-based ceramic tool materials were designed according to the above proposed models. One was Al2Oμ-TiCμ-TiCn-Co composite ceramic tool material, and the volume content of micro-scale Al2O3, micro-scale TiC, nano-scale TiC and cobalt were56%,35%,6%and3%repectively, the other one was Al203μ-(W,Ti)Cμ-TiCn-Ni/Co composite ceramic tool materials, and the volume content of micro-scale Al2O3, micro-scale TiC, nano-scale TiC and Ni/Co were57%,33%,6%and4%respectively.The influences of nano-particle content and metallic phase content on the room temperature mechanical properties and microstructure were investigated. The results showed that when the content of nano-scale TiC particles was6vol.%, the ratio of intergranular fractured grains to transgranular fractures grains in the materials was suitable and resulted in the better flexural strength and fracture toughness. These results verified the validity of the mathematical model of the optimal content of nano-scale particles. When the content of cabalt was too low or too high, the mechanical properties of the ceramic tool materials would reduce and there was an optimal content of the cabalt. These results verified the validity of the mathematical model of the optimal content of the metallic phase.The sintering technologies of the composite ceramic tool materialswere optimized. It was found that Al2O3-TiCμ-TiCn-Co micro-nano-composite tool material which was sintered under a pressure of32MPaand a temperature of1650℃in vacuum for20min, had optimum mechanical properties. Its flexural strength, fracture toughness and Vicker’s hardness were916MPa,8.3MPa·m1/2and18GPa, respectively. For the Al2O3μ-(W,Ti)Cμ-TiCn-Co composite ceramic tool material, the best flexural strength, fracture toughness and Vicker’s hardness were882MPa,7.2MPa·m1/2and19GPa, which was sintered under a pressure of32MPa and a temperature of1650℃in vacuum for30min.The strengthening and toughening mechanisms of the composite ceramic tool materials were detailedly studied. It was found that the strengthening and toughening mechanisms of micro-scale particles was grain bridge and cracks deflection. The strengthening and toughening mechanisms of nano-scale particles was grain boundary pinning, grain refining, cracks re-deflection and transgranular fracture. The strengthening and toughening mechanisms of metallic phase was the reduction of the residual tensile stress distributed in matrix and the increase of the interfacial bonding strength.The high temperature mechanical properties and dynamic fatigue behavior of composite ceramic tool materials were deeply investigated. The change regulation of the high temperature mechanical properties and dynamic fatigue behavior with the temperature was revealed. The slow propagation mechanism model of crack at high temperature was built. The weakening mechanisms of the mechanical properties at high temperatures were analysed. The results showed that the flexural strength of Al2O3-TiCμ-TiCn-Co composite decreased with an increase in temperature, and the fracture toughness decreased as a function of the temperature up to1000℃but increased at1200℃due to small plastic defomation. The difference between the room temperature flexural strength s and the high temperature flexural strength was smaller for the composite ceramic tool materials without cabal. However, the excess cobalt led to the decreased the high temperature flexural strength, and the more the content of cobalt, the highly the high temperature flexural strength was dropped. The sub-caracks were propagated in ceramic materials at room and high temperature. The fatigue resistance of the materials at high temperature was greatly dropped. Appropriate metallic phase could improve the anti-fatigue property of ceramic tool materials. The weakening mechanisms of the high temperature flexural strength of Al2O3-TiCμ-TiCn-Co was oxidative attack and microstructure damage, grain boundary softening of metallic phase at high temperature, the reduction of interfacial bonding strength, crack intragranular propagation and fracture, the reduction of elastic modulus at high temperature, plastic deformation, and grain boundary defects caused by grain boundary migration. The fatigue failure mechanism of Al2O3-TiCμ-TiCn-Co composite tool material at room temperature and900℃was ascribed to stress-corrosion cracking, but at1200℃the failure mechanism was creep.The cutting performance and cutting reliability of the multi-scale particles reinforced Al2O3-based ceramic cutting tools were researched. The model of the relationship between the dynamic fatigue property of the ceramic tool materials and the tool life by fatigue wear was established. The distribution models of the tool life by wear and the cutting reliability medels were built. The cutting performance and cutting reliability of the composite ceramic tools when continuous cutting austenitic stainless steel (1Cr18Ni9Ti) were studied. The results showed that when wet cutting1Cr18Ni9Ti with the ATTC ceramic cutting tools (b=0.1mm, r=0.1mm) at a cutting speed of80m/min, a feed rate of0.15mm/r and a depth of cut of0.1mm, the metal removal volume was the greatest, and the tool life was13min. The tool life by wear obeyed the Gamma distribution. When the cutting tool reliability was0.5, the reliable tool life by wear was about9min. When the cutting tool reliability increased to0.8～0.9, the reliable tool life by wear was about5.5-6.5min. The best wear resistance of four kinds of cutting tools was ATTC(b=0.1mm, r=0.1mm), followed by ATTC(b=0.3mm, r=0.3mm), LT55and AWTC. The failure patterns of cutting tool were mainly cutting edge brittle fracture and tool material peeling off the tool clearance caused by fatigue breakage, and the main failure mechanisms were abrasive wear and adhesive wear. The cutting performance and cutting reliability of the composite ceramic tools when continuous cutting cold work die steel (Cr12MoV) were studied. When wet cutting Cr12MoV with the ATTC ceramic cutting tools at a cutting speed of60m/min, a feed rate of O.lmm/r and a depth of cut of0.1mm, the surface roughness was the best and the tool life by waer was9min. The tool life by wear obeyed the lognormal distribution. When the cutting tool reliability was0.5, the reliable tool life by wear was about1.5min. When the cutting tool reliability increased to0.8-0.9, the reliable tool life by wear was about4.5-5.3min. For the ATTC cutting tools with different corner radius and chamfer width, the best surface roughness was got when using the ATTC tool with a larger corner radius and chamfer width in wet cutting. When wet cutting Cr12MoV, the failure patterns of cutting tool were mainly groove wear, boundary wear, tool material peeling off the tool clearance and tool tipping, and the main failure mechanisms were abrasive wear and adhesive wear.更多还原