Al2O3／SiCW陶瓷刀具材料中晶须的取向对其力学和切削性能的影响

Ａｌ２Ｏ３／ＳｉＣＷ陶瓷刀具材料由于热压过程的影响，造成晶须在基体中定向排布于垂直热压方向的平面上，因此不同方向的补强、增韧效果有所差异。本工作测量了Ａｌ２Ｏ３／ＳｉＣＷ陶瓷刀具材料不同方向上的断裂韧性和抗弯强度，分析了晶须的取向对该陶瓷刀具材料力学性能的影响。切削试验表明晶须的取向对晶须增韧陶瓷刀具材料的磨损和破损性能有较好的影响。根据切削加工过程中刀具的受力特点，提出了有利于切削加工的刀具前、     

SiC晶须对Al2O3／TiB2／SiCw陶瓷刀具材料高温断裂韧性的影响

研究了不同ＳｉＣ晶须含量的Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣｗ陶瓷刀具材料的断裂韧性随温度的变化规律。结果表明：Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣＷ陶瓷材料的Ｋ１Ｃ在１０００℃内随温度的升高而增大；晶须含量越大，通过计算分析表明，随温度的升高粘裂时拔出的晶须大大增多，当晶须体积含量（下同）为２０％时，Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣｗ陶瓷在室温时只有长径比小于２．８７的晶须在断裂时才有可能产生拔出，而在９００℃时     

新型复相陶瓷刀具材料Jx-2-I协同增韧补强机理的研究

本文研制成功的新型陶瓷刀具材料—ＳｉＣ晶须（ＳｉＣｗ）增韧和ＳｉＣ颗粒弥散增韧Ａｌ２Ｏ３陶瓷刀具Ｊｘ－２－Ｉ,该刀具材料具有高的抗弯强度和断裂韧性等优点;对比Ａ（Ａｌ２Ｏ３）、ＡＰ（Ａｌ２Ｏ３／ＳｉＣｐ）、ＡＷ（Ａｌ２Ｏ３／ＳｉＣｗ）、Ｊｘ－１（Ａｌ２Ｏ３／ＳｉＣｗ）和Ｊｘ－２－１（Ａｌ２Ｏ３／ＳｉＣｐ／ＳｉＣｗ）等陶瓷材料的力学性能可以看出,在Ｊｘ－２－Ｉ材料中具有明显的增韧补强叠加效应;本文在热失配分析和微观结构观察的基础上详细研究了Ｊｘ－２－Ｉ刀具材料的增韧补强机理,系统研究了Ｊｘ－２－Ｉ中各种增韧补强机理之间的协同效应。     

新型复相陶瓷刀具材料JX—2—Ⅰ协同增韧补强机理的研究

本文研制成功了一种新型陶瓷刀具材料－ＳｉＣ晶须增韧和ＳｉＣ颗粒弥散增韧Ａｌ２Ｏ３陶瓷刀具ＪＸ－２－Ⅰ，     

几类典型结构陶瓷材料的冲蚀磨损行为研究

研究了几类典型结构陶瓷材料，如Ａｌ２Ｏ３，ＳｉＣ，Ｓｉ３Ｎ４陶瓷，Ａｌ２Ｏ３－ＺｒＯ２系相变增韧陶瓷（ＺＴＡ，ＴＺＰ）和ＳｉＣｗ／Ｓｉ３Ｎ４系晶须补强陶瓷（ＷＲＳＮ）有９０ｍ／ｓ下的冲蚀磨损性能，以及其与材料性能（硬度，断裂韧性）和冲蚀条件（粒子硬度，冲击角度）之间的关系，分析了冲蚀磨损机制。陶瓷材料的低角冲蚀磨损机制主要包括：研磨状损伤，犁沟状微切削损伤和晶粒剥落。低角冲蚀磨损率随材料硬度的增加     

Al2O3／TiB2／SiCW陶瓷刀具加工镍基合金时的磨损机理研究

研究了Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣＷ陶瓷刀具加工Ｉｎｃｏｎｅｌ７１８镍基合金时的切削性能和磨损机理。结果表明；在低速切削条件下，Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣＷ和硬质合金刀具的抗后刀面磨损的能力相差不大；而在高速切削条件下，前者的抗后刀面磨能力远高于后者。     

SiC_w一AlN复合材料工艺因素的研究

本文研究了工艺因素（烧结温度、添加剂组成和含量）对ＳｉＣ＿ｗ一ＡＩＮ复合材料的影响。结果表明：１８５０℃是较合适的复合材料烧结温度，复合材料力学性能与添加剂组成和含量有密切关系。Ｙ＿２Ｏ＿３与ＳｉＯ＿２在烧结中起的作用不同，Ｙ＿２Ｏ＿３与ＡＩＮ表面的Ａｌ＿２Ｏ＿３形成液相，是一种良好的烧结添加剂，而ＳｉＯ＿２由于与ＡＩＮ形成２７ＲＳｉａｌｏｎ多形体，反而阻碍材料致密化。在添加８ｗｔ％左右Ｙ＿２Ｏ＿３时。复合材料力学性能最佳，抗折强度σ５２０ＭＰａ，断裂韧性Ｋ＿（ｌｃ）＝４．９８ＭＰａ·ｍ￣（１／２）     

SiCw增韧Al2O3／TiB2陶瓷复合材料的研究

根据对晶须与基体材料的热胀失配的分析，计算得出了Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣｗ三元复合材料中ＳｉＣｗ的临界体积分数。采用ＴｉＢ２颗粒增韧和ＳｉＣｗ增韧两种途径来改善Ａｌ２Ｏ３的脆性，得到此复合材料的抗弯强度为７４０ＭＰａ，断裂韧性为７．７ＭＰａ·ｍ＾１／２。分析表明：当ＳｉＣｗ含量大于临界体积分数时，强度大幅降低的主要原因是由于致密度的降低和热残余拉应力的增大。     

C－B_4C－SiC复合材料抗氧化性能的研究

对碳／陶瓷复合材料（Ｃ－Ｂ＿４Ｃ－ＳｉＣ）的抗氧化性能进行了研究，结果表明：Ｃ－Ｂ＿４Ｃ－ＳｉＣ复合材料抗氧化性能比碳素材料大大提高，而且烧结助剂对Ｃ－Ｂ＿４Ｃ－ＳｉＣ复合材料的抗氧化性能影响很大。在复合材料中分别加入了Ａｌ，Ａｌ＿２Ｏ＿３，Ｎｉ，Ｔｉ，ＴｉＣ，Ｓｉ等不同烧结助剂，发现添加Ｎｉ的材料抗氧化性能最佳，经１０００℃氧化１５ｈ后，氧化度小于０．５％；加入Ｔｉ，Ｓｉ和ＴｉＣ的次之，不加烧结助剂的又次之，加入Ａｌ和Ａｌ＿２Ｏ＿３的最差。     

导电Al2O3基陶瓷刀具材料的超声—放电复合加工技术研究

采用超声－放电复合加工技术对Ａｌ２Ｏ３／（Ｗ,Ｔｉ）Ｃ,Ａｌ２Ｏ３／ＴｉＢ２,Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣｗ三种Ａｌ２Ｏ３基陶瓷刀具材料表面定位方孔进行加工,研究了共加工机理和加工参数对不同陶瓷材料加工效率,加工表面粗糙度的影响,由于该复合加工技术有产地结合了超扬波加工和放电加工的特点,因而能高效,高质量地加工陶瓷材料。试验结果表明,在同样的加工条件下,材料去除率的大小顺序为Ａｌ２Ｏ３／（Ｗ,Ｔｉ     

SiC晶须增强Al2O3—TiC复相陶瓷的研究

运用品须补强和粒子弥散双重手段,对氧化铝材料的性能进行改进。比较了Al_2O_3-TiC(AT),Al_2O_3/SiC_w(As),Al_2O_3-TiC/SiC_w(ATS)材料的力学性能,证实ATS材料有明显的迭加增强增韧效果,并具有良好的高温力学性能。抗氧化实验证实,将SiC晶须加入AT中以后,材料的抗氧化性能有明显改进。从热膨胀失配角度分析和SEM显微结构观察证实,ATS材料的主要增韧机理是界面解离和裂纹偏转。     

SiCw／涂层／TZP陶瓷复合材料界面化学键的XPS和IR研究

本文用ＸＰＳ和ＩＲ测定了ＳｉＣｗ／（Ａｌ２Ｏ３，莫来石）涂层／ＴＺＰ陶瓷复合材料的界面化学键。结果表明ＳｉＣｗ／Ａｌ２Ｏ３、莫来石、ＴＺＰ界面为化学结合而Ａｌ２Ｏ３、莫来石／ＴＺＰ界面为物理结合。     

氧化对Al_2O_3－TiB_2陶瓷刀具材料磨损特性的影响

研究了Ａｌ_２Ｏ_３－ＴｉＢ_２陶瓷刀具材料的高温氧化特性以及氧化对刀具耐磨性能的影响。结果表明：随ＴｉＢ_２含量的增加，Ａｌ_２Ｏ_３－ＴｉＢ_２的氧化活化能降低，抗氧化能力下降．Ａｌ_２Ｏ_３－ＴｉＢ_２刀具材料在加工淬火钢时，因切削高温的氧化作用在刀具表面生成的ＴｉＯ_２既可减轻刀具的粘结磨损，又能起到固体润滑剂的作用，从而降低摩擦系数，因而提高刀具的耐磨性能。当切削速度大于１５０ｍ／ｍｉｎ时，随ＴｉＢ_２含量的增加，刀具抗磨损能力显著提高。     

Al2O3—TiB2陶瓷刀具材料的高温氧化及其对刀具耐磨性能的影响

研究了Ａｌ２Ｏ３－ＴｉＢ２陶瓷刀具材料在１０００℃下的氧化行为，用ＸＲＤ、ＳＥＭ分析了氧化后的相组成及显微结构。结果表明：Ａｌ２Ｏ３－ＴｉＢ２陶瓷材料在１０００℃空气中氧化增重符合抛物线规律；随ＴｉＢ２含量的增加，该材料的抗氧化能力下降。     

MnO2对自蔓延高温合成陶瓷复合钢管陶瓷层结构和性能的影响

采用MnO2作为添加剂自蔓延高温合成法制备了具有Al2O3和FeAl2O4陶瓷层的复合钢管,研究其对陶瓷层和过渡层的结构和性能的影响.结果表明:添加了MnO2后,陶瓷层表面晶粒排布更加致密,陶瓷层的内表面为层叠状的Al2O3细晶和少量的FeAl2O4;过渡层为Al2O3和混入的FeAl2O4外,还含有SiO2和MnO2,过渡层出现了向钢基体中渗透的网状结构.MnO2的加入并未改变复合钢管Al2O3和FeAl2O4陶瓷层的物相.加入4%(质量分数)MnO2的复合管的抗压度强度和陶瓷层的抗剪强度分别达到416 MPa和19.2 MPa,比未添加MnO2的样品分别提高了18.2%和12.3%     

新型陶瓷刀具的切削性能研究

本文研究了山东工业大学机械工程学院研制的新型陶瓷刀具材料（包括ＪＸ－２，Ｈ５，Ｈ１３和Ｈ２１等）分别切削铸铁（ＨＴ２０）淬火４５号钢和难加工材料ＧＨ９９时的切削性能，探讨了各陶瓷刀具的抗磨损能力，实验研究了切削速度和进给量对刀具磨损的影响，并对切削条件进行了优化。     

Self-lubricating behaviors of Al2O3/TiB2 ceramic tools in dry high-speed machining of hardened steel

In this paper, Al₂O₃/TiB₂ ceramic cutting tools with different TiB₂ content were produced by hot pressing. The fundamental properties of these ceramic cutting tools were examined. Dry high-speed machining tests were carried out on hardened steel. The tool wear, the cutting temperature, the cutting forces, and the friction coefficient between the tool and the chip were measured. It was shown that both the wear rates and the friction coefficient at the tool–chip interface of Al₂O₃/TiB₂ ceramic cutting tools in dry high-speed machining of hardened steel were reduced compared with that of in low-speed machining. The mechanisms responsible were determined to be the formation of a self-lubricating oxide film on the tool–chip interface owing to the tribological–chemical reaction by the elevated cutting temperature. The composition of the self-lubricating film was found to be the oxidation product of TiB₂ grains, which serves as lubricating additive on the wear track of the tool rake face. The appearance of this self-lubricating oxide film contributed to the improvement in wear resistance and the decrease of the friction coefficient. This action was even more effective with higher TiB₂ content. Cutting speed was found to have a profound effect on the self-lubricating behavior. In dry low-speed machining of hardened steel, the Al₂O₃/TiB₂ tools showed mainly adhesive and abrasive wear. While in dry high-speed machining, oxidation wear of the ceramic tools was the dominant mechanism due to the very high cutting temperature. No oxide film was formed on the tool–chip interface while machining in nitrogen atmosphere, and the tool wear resistance was correspondingly decreased.     

Fabrication and Properties of Closed-pore Al_2O_3-based Refractory Aggregates

A novel Al_2O_3-based refractory aggregate with closed-pore structure was fabricated utilizing superplasticity with submicro-sized Al_2O_3 and MgO as raw materials,and SiC as a high temperature pore-forming agent.The effect of MgO on porosity,phase composition and microstructure of the refractory aggregate has been investigated. For comparison,the common Al_2O_3-based refractory aggregates and porous ones with open-pore structure were also prepared. The results indicate that the closed porosity of Al_2O_3-based refractory aggregate increases as the content of MgO increases. When the content of MgO is 15 mass%,the closed and apparent porosities are 14. 5% and 1. 1%,respectively. The main phase compositions are Al_2O_3 and MgAl_2O_4. The formation mechanism of closed pores is that the fine-crystallinegrain Al_2O_3 ceramic possesses superplastic deformation ability after adding MgO at high temperatures. When SiC powder is added to the Al_2O_3 ceramic,the generated gases by the reaction of SiC at the sintering temperature can provide a pressure to make grain boundaries slide. Then,the gases are enclosed by crystalline grains to form the closed pores. The slag corrosion resistance of the fabricated closed-pore Al_2O_3-based refractory aggregate is better than the common refractory aggregate and porous ones.     

Reliability prediction of a microwave sintered Si3N4-based composite ceramic tool

The wear life reliability prediction model of microwave sintered Si₃N₄/(W,Ti)C/Y₂O₃/MgO/Al₂O₃ composite ceramic tools based on the random distribution characteristics of hardness and fracture toughness of ceramic tool material was established. It showed that the Vickers hardness of ceramic tool materials followed a normal distribution and the fracture toughness followed a lognormal distribution. Distribution law of wear life can be determined by the joint distribution of hardness and fracture toughness. Experimental research on tool reliability of continuous dry cutting quenched high quality carbon steel T10A was carried out and the applicability of the tool reliability prediction model was verified. The results showed that the error between the theoretical reliable life and the actual life of the ceramic tool was less than 5% under the same reliability when the reliability was above 0.5.     

Wear simulation of Si3N4 cutting tool material on a pin-on-disc tester

Si₃N₄-based ceramic cutting tools are used nowadays for machining cast iron, nickel-based alloys, etc. Austenitic stainless steel AISI 321 is one of the most difficult to cut materials. In order to investigate the wear behaviour of Si₃N₄ ceramic when cutting the stainless steel, wear tests are carried out on a pin-on-disc tribometer, which can simulate a realistic cutting process. The selected load range is from 58.8 N to 235.2 N, the speed range is from 0.8 m/s to 3.2 m/s. The test results show that the wear of Si₃N₄ ceramic increases with both load and speed and the wear of the ceramic is mainly caused by adhesion between the rubbing surfaces. Scanning electron microscope (SEM), electron probe microanalyser (EPMA) and energy dispersive X-ray analyser (EDXS) were used for examinations of the worn surfaces. The wear mechanisms of Si₃N₄ ceramic sliding against the stainless steel were discussed in detail.