人工神经网络在Al2O3/TiC/SiC多相陶瓷刀具材料开发中的应用

复相陶瓷刀具材料应用前景广阔。利用基于BP算法的人工神经网络技术,建立了预测颗粒增韧多相陶瓷刀具材料各组分体积百分含量的预测模型,模型应结合材料性能合理确定输入参数。利用该模型实际开发了Al2O3/TiC/SiC系复相陶瓷刀具材料,材料的力学性能满足要求。     

氮化硅陶瓷水煤浆喷嘴的损坏机理

用热压烧结法制备了Si3N4/TiC和Al2O3/TiC陶瓷水煤浆喷嘴.测量了喷嘴的磨损质量损失,用扫描电子显微镜观察了喷嘴磨损后的表面形貌,研究了其磨损特性.结果表明:陶瓷水煤浆喷嘴材料的硬度和断裂韧性对其热冲蚀磨损有重要影响.在相同条件下,硬度较高的Al2O3/TiC陶瓷喷嘴的磨损率较低,而断裂韧性较高的Si3N4/TiC陶瓷喷嘴的热冲击损伤较小.陶瓷喷嘴磨损表面因区域不同而显示不同的特征,Si3N4/TiC陶瓷喷嘴的损坏机理主要表现为塑性变形、脆性断裂、研磨损伤、热裂纹和热崩.     

Al2O3/TiC复合陶瓷拉丝模材料的摩擦磨损性能

采用热压法制备出Al2O3/TiC复合陶瓷材料,该材料具有良好的综合力学性能,抗弯强度为850MPa,断裂韧性为4.9MPa·mi/2.由高速环块磨损试验机对其摩擦磨损行为及其磨损机理作了试验研究.用扫描电镜观察了磨损表面形貌.结果表明Al2O3/TiC复合陶瓷拉丝模材料磨损率随试验转速升高而下降,但压力变化对磨损率的影响不大.Al2O3/TiC复合陶瓷拉丝模材料磨损机理主要是脆性脱落和犁沟,具有良好的耐磨性.是制备拉丝模的优良材料.     

热压烧结法制备碳化钛/氧化铝复合材料

把TiC颗粒和金属Al以AlTiC中间合金的形式引入Al2O3陶瓷中,用过渡液相热压烧结法制备了TiC/Al2O3复合材料,并对其微观结构与力学性能进行了研究。结果表明:在1450℃,30MPa条件下,热压烧结制备的TiC/Al2O3复合材料中TiC与Al2O3能稳定共存,材料的断裂韧性和Vickers硬度均有明显提高。材料的Vickers硬度平均超过23.5GPa,断裂韧性超过8.7MPa·m1/2,密度低于纯Al2O3的。由于添加相AlTiC和Al2O3的成本均较低,因而找到了一种低成本制造高性能TiC/Al2O3复合材料的方法。     

Si3N4/TiC纳米复合陶瓷刀具材料氧化行为

在微米Si3N4基体中加入纳米Si3N4及TiC颗粒,以Al2O3和Y2O3作为助烧结剂,通过热压烧结制备了Si3N4/TiC纳米复合陶瓷刀具材料,研究了该材料在800～1 250℃时的氧化行为.结果表明:该类材料的氧化特性符合抛物线规律;随TiC含量的增加,材料的抗氧化性能降低.由氧化后样品的X射线衍射谱分析可知:氧化表面生成SiO2和TiO2,表面仅余微量的Si3N4和TiC成分,表明经1 250℃,100h氧化后,样品表面几乎被氧化物覆盖.Si3N4/TiC(含有10%纳米Si3N4和15%TiC,质量分数)纳米复合材料在经过900℃,100h氧化后,其强度无明显下降;但经过1000℃,100h的氧化后,材料的强度已经降至氧化前的41%.扫描电镜观察表明裂纹的生成及扩展是引起强度降低的主要原因.     

新型Ti(C,N)基金属陶瓷刀具的磨损性能

金属陶瓷由于具有优良的综合性能而广泛用作刀具材料.本文研究了纳米TiN改性TiC基金属陶瓷刀具的组织及其在加工正火态45号钢时的磨损性能.结果表明,与传统金属陶瓷相比,新型金属陶瓷的组织更细小.与传统金属陶瓷刀具、Al2O3刀具及YT15硬质合金刀具相比,新型金属陶瓷刀具具有更高的刀具寿命和切削效率,且主要以"磨损"形式失效.     

FeTiO3-Al-C系统的反应热力学及Al2O3-TiC/Fe 复合材料的制备

充分利用天然矿物钛铁矿（FeTiO3）中的铁和钛,采用反应烧结技术,成功制备了Al2O3-TiC/Fe陶瓷复合材料.在真空热压炉中实现了合成与烧结一体化,为陶瓷复合材料的低成本制备进行了有益的探索研究.对钛铁矿-Al-C系统的热力学过程进行了详细的理论分析.研究表明：系统主要发生铝热还原反应,中间产物为多种钛的氧化物,系统反应后热力学上最为稳定的物质为Al2O3,TiC和Fe;系统反应最高温度低于Al2O3的熔化温度.通过实验研究,分析了产物的物相、结构和性能.反应烧结的最终产物主要为TiC,Al2O3和Fe.此外,还有少量Fe-Al相,大部分为Al2O3.TiC晶体颗粒尺寸约为3～5 μm,分布较为均匀,Fe分布于Al2O3,TiC晶粒之间.Y2O3和Cr2O3添加剂可以提高复合材料的抗弯强度.     

机械切削领域陶瓷刀具研究进展及趋势

在高速度、低切削力的切削加工领域中,陶瓷刀具的使用日益普遍,是一个新兴的极具发展潜力的研发方向.陶瓷刀具不仅可以在保证产品质量的前提下为生产实际创造巨大的经济效益,还可以节省数量可观的能源,从而达到能够节能减排、保护环境的目的.本文将介绍当前以刚玉基(Al2O3)和氮化硅基(Si4N3)为代表的陶瓷切削刀具的研究进展及发展趋势.     

金刚石复合片刀具磨损机理研究

选用平均粒度10微米的金刚石复合片制成刀具,对高硅铝合金(Al-30wt%Si)进行切削实验。通过扫描电子显微镜分析了工件的形貌以及金刚石刀具前后刀面磨损的微观形貌。其磨损程度与切削路程为线性关系,金刚石刀具的磨损主要是后刀面机械摩擦磨损以及前刀面的粘接磨损,而没有出现像立方氮化硼刀具的化学磨损以及月牙洼磨损。     

SiC晶须增韧Al_2O_3陶瓷刀具材料的增韧特性及其对刀具破损的影响

在微观结构研究的基础上,分析了SiC晶须增韧Al_2O_3陶瓷刀具材料的增韧特性和机理。由于受热压过程的影响而造成晶须在基体中定向排布于垂直热压轴方向的平面中,因此不同方向的增韧效果有所差异,而且选取不同平面作为刀具前刀面时在切削中抗破损能力亦不同。研究表明,断续切削时,由于刀头內应力分布的影响,选用平行于热压轴方向的平面作为前刀面将使其获得更高的抗破损能力。     

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.     

Cutting performance and wear mechanisms of the graphene-reinforced Al2O3-WC-TiC composite ceramic tool in turning hardened 40Cr steel

The Al₂O₃-WC-TiC-graphene composite ceramic tool (AWTG0.5) fabricated by two-step hot pressing was used to continuously turn the hardened 40Cr steel at different cutting speeds, and its cutting performance and wear mechanisms were compared with the homemade graphene-free AWTG0 ceramic tool and the commercial ceramic tools SG4 and LT55. The cutting performance of the AWTG0.5 tool was significantly better than that of the AWTG0, SG4 and LT55 tools. The contributions of graphene to the mechanical properties, lubricating properties and thermal conductivity of the AWTG0.5 tool were responsible for its higher cutting performance. The main wear mechanisms of the AWTG0.5 tool were adhesive wear and abrasive wear. In addition, it was also found that the anti-friction and wear resistance performances of the AWTG0.5 tool were superior to those of the other three tools. Its good anti-friction and wear resistance performances could be attributed to the formation of a self-lubricating layer induced by graphene pull-out.     

Investigation of novel multiscale textures for the enhancement of the cutting performance of Al2O3/TiC ceramic cutting tools

Currently, the high temperature and severe friction conditions at the tool-chip interface are the main reasons for ceramic tool wear failures. Surface texturing as a geometric extension for cutting tools is a promising way to extend their service life. In this study, a novel type of multiscale texture was developed, and its effect on the cutting performance of an Al₂O₃/TiC ceramic cutting tool while machining AISI H13 steel was explored in a conventional cooling environment. The cutting force, cutting temperature, and tool wear morphology were investigated at cutting velocities ranging from 80 to 249 m/min. Microgroove textured Al₂O₃/TiC ceramic tools were prepared for comparison. The results show that the structure of the multiscale textures maintained good integrity over the range of cutting velocities. Thus, the synergistic effect of the microscale and nanoscale textures promoted the introduction and permeation of the cutting fluid. Therefore, the multiscale textures effectively enhanced the cutting performance of the Al₂O₃/TiC ceramic tools.     

Improvement of cutting performance of SiAlON ceramic by texture engineering in turning superalloys

High speed and high efficiency machining of superalloy is a big technological challenge faced by the cutting tool industry in the world. In the present study, cutting performance of nickel-based superalloy was significantly improved by engineering the texture of SiAlON ceramic cutting tools with grains oriented parallel to the cutting edge. Orientation of the rod-like grains played a significant role in the wear resistance of SiAlON ceramic. With the rod-like grains parallel to the cutting edge of the tool, the resistance to notched wear and peeling was much higher, resulting in slow and stable flank and rake wear. The tool life of the textured tool with rod-like grains parallel to the cutting edge was 17% higher than that of the untextured tool. On the other hand, for the tools with the grains perpendicular to the rake or flank face, the friction generated during machining would be parallel to the grain direction, which led to the rapid peeling on the tool surface along the moving direction of the workpiece or the chip flow direction, resulting in rapid tool wear. The preferred orientation of mechanical properties designed by engineering grain orientation provides the possibility to optimize the cutting performance of SiAlON ceramic tool in turning superalloys.     

硬质合金粉末表面涂层陶瓷的材料

利用溶胶－凝胶法在ＴｉＣ粉末,（Ｗ,Ｔｉ）粉末表面涂层Ａｌ２Ｏ３陶瓷,通过热压烧结制得了两种新型涂层的刀具材料（ＦＴＣ１和ＦＴＣ２）,粉末涂层材料ＦＴＣ１和ＦＴＣ２的力学性能满足刀具材料的使用要求。利用扫描电镜观察发现基体粉末表面较均匀地涂覆了一层α－Ａｌ２Ｏ３陶瓷,并对材料的力学性能和微观结构进行了分析。     

Tool life and wear of WC–TiC–Co ultrafine cemented carbide during dry cutting of AISI H13 steel

WC–5TiC–10Co ultrafine cemented carbides were prepared and used for the cutting tool for AISI H13 hardened steel. The effect of cutting parameters on the tool life and tool wear mechanism was investigated, and conventional cemented carbide with the same composition and medium grain size were prepared for comparison. The results showed that WC–5TiC–10Co ultrafine cemented carbides possess higher hardness and transverse rupture strength, and showed better cutting performance than conventional insert with the same cutting condition. Tool life was analyzed by an extended Taylor's tool life equation, indicating that cutting speed played a profound effect on the tool life and wear behavior of both cutting inserts. SEM and EDS analysis revealed that there were major adhesive wear and minor abrasive wear on the rake of WC–5TiC–10Co ultrafine inserts, and increase of cutting speed resulted in a transition from abrasion predominant wear mechanism to adhesive wear on the flank face. As for the conventional inserts, there were combination of more serious abrasive and adhesive wear on the rake and flank. The favorable cutting performance of ultrafine WC–5TiC–10Co inserts was attributed to the higher hardness and less thermal softening during machining.     

Friction and wear behavior of microwave sintered Al2O3/TiC/GPLs ceramic sliding against bearing steel and their cutting performance in dry turning of hardened steel

An Al₂O₃/TiC/GPLs (ATG) composite ceramic tool material was fabricated by microwave sintering. The tribological properties of ATG during sliding against GCr15 bearing steel were studied, to investigate the effects of sliding speed and normal load on the friction coefficient and wear rate. In addition, the cutting performance of ATG tools for machining of hardened alloy 40Cr steel was experimentally studied and compared with those of commercial tools. The results showed that the added graphene platelets enhanced the wear resistance and reduced the friction coefficient of the tool material. Furthermore, upon adding graphene platelets, the ability of the tools to resist breakage and their cutting depth improved. The cutting length of the microwave- sintered ATG ceramic tools was approximately 125% higher than that of hot-pressed ceramic tools and 174% higher than that of cemented carbide tools.     

Performance of Si3N4/(W,Ti)C graded ceramic tool in high-speed turning iron-based superalloys

A Si₃N₄/(W, Ti)C graded nano-composite ceramic tool was fabricated and its performance in high speed turning iron-based alloys GH2132 was investigated compared with homogeneous and commercial ceramic tools. The chip morphology, cutting forces, cutting temperature, tool life and failure mechanisms and machined surface roughness were recorded and analyzed. The results showed that with the increasing cutting speed the resultant cutting force shows a tendency to first increase and then decrease while the cutting temperature increases gradually. Straight continuous chips, bending continuous chips, twist continuous chips and snarled chips form in turn. Saw-tooth chips tend to form when the cutting speed is more than 200?m/min. The graded tool shows longer tool life especially at the cutting speed of 150 and 200?m/min compared with the homogenous and commercial ceramic tools. Tool failure modes mainly include grooving on the rake face, notching on the flank face, abrasion and adhesion. The grooving on the rake face tends to decrease while notching on the flank face tends to increase as cutting speed increases. Surface roughness of the machined iron-based super-alloys is relatively high due to the serious adhesion. Better surface roughness can be got using the graded tool.     

Experimental investigation of different morphology textured ceramic tools by in-situ formed for the dry cutting

Surface texture is considered an important measure to improve the cutting performance of a tool. In this study, we have prepared three types of textured and conventional tools on the rake face by an in-situ formed method. During the experiment, the best parameters of three types of textured tools were selected for dry cutting AISI 1045 steel at different cutting speeds. Cutting forces, cutting temperatures, workpiece surface roughness, and tool wear were measured during the cutting process. The results showed that textured tools have significantly reduced cutting force, cutting temperature, and tool wear, and the roughness of the workpiece was improved compared with the conventional tool. The micro-pit texture tool has less stress contact region than the micro-groove width texture tool, but the micro-groove width texture tool exhibiting the best cutting performance. This investigation clearly showed that the textured tool prepared by the in-situ formed method has improved cutting performance.