Papers by Keyword: Ceramic Tool

Abstract: The purpose of this study is to develop ZTA-MgO-MWCNT cutting insert with enhanced properties and excellent tool performance that is suitable for high-speed machining. The effects of MWCNT addition on the physical properties of ZTA-MgO composites were investigated. The samples were fabricated using 80:20 composition (80 wt.% of Al2O3: 20 wt.% of YSZ) with fixed amount of MgO at 1.1 wt.% and MWCNT ranging from (0.1 – 0.5 wt.%) as secondary additives. The CNT was pre-treated in ethanol for 1 hour using an ultrasonic homogenizer before mixing and ball milled with Al₂O₃, YSZ and MgO compositions for 24 hours. The mixture is then pressed at 100 MPa into round-shaped cutting inserts mold after being dried at 100°C for 24 hours. The pressed samples were sintered at 1600 oC for 4 hour soaking time. XRD, density, porosity and shrinkage analysis performed on the samples. The XRD analyses indicate the presence of major phases were α-Al₂O₃, ZrO₂, Zr_0.963Y_0.037O_1.982 and MgAl₂O₄. The effect of MWNT addition on density, porosity and shrinkage of ZTA-MgO shows that density (4.210 g/cm3) and percentage of shrinkage (8.05%) obtained the highest value by 0.2 wt.% MWCNT compared with samples without CNT additives which is only 4.020 g/cm3 and 7.05% respectively. High density value indicates that the shrinkage percentage is also high, which corresponds to the densification of the composites. Poor dispersion of MWCNT within the matrix is highly accounted for agglomeration around Al₂O₃ grain boundaries and decreases in densification.

Abstract: In this paper, the dry cutting performance of Al₂O₃/TiC-based ceramic composites with nanoCaF₂ was studied. Compared with the Al₂O₃/TiC ceramic tool, the Al₂O₃/TiC/CaF₂ ceramic tool has lower cutting force, cutting temperature and surface roughness when milling 40Cr hardened steel. Three cutting parameters of cutting speed, feed per tooth, and cutting depth were used to conduct orthogonal experiments to study its changing trend. Through testing of cutting force, cutting temperature and surface roughness, and by comparison with ceramic tools without nanosolid lubricant added, the order of influence of three cutting parameters on cutting force, cutting temperature and surface roughness was obtained. The experimental results showed that the cutting force, cutting temperature and surface roughness of Al₂O₃/TiC/CaF₂ ceramic tools containing nanoCaF₂ werebetter than those of Al₂O₃/TiC ceramic tools. The cutting force, the cutting temperature, and the surface roughness were respectively reduced by 16.5%, 25.8% and 43% compared to when no solid lubricant was added. In addition, after adding solid lubricant, the effect of cutting depth on cutting force was significantly reduced. The average friction coefficient of the tool rake surface was 31.1% lower than that of ceramic tools without solid lubricant. In order to explain this phenomenon, through scanning electron microscopy (SEM) scanning and energy spectroscopy (EDS) elemental analysis, the wear reduction mechanism of solid lubricants was analyzed, that is, during the cutting process, nanosolid lubricants precipitated and formed lubricating film on the rake surface of the tool to reduce the friction coefficient. This was also the main reason for reducing the cutting temperature.

Abstract: The purpose of this study is to investigate the phase transformation route of ZTA-MgO ceramic cutting tool in raw powder form, after sintering process and after machining process. This is to evaluate the effect of phase transformation to the properties of the cutting tool i.e hardness and fracture toughness. Samples of ZTA-MgO ceramic cutting insert were fabricated by wet mixing the materials, and then dried at 100°C before crushed into powder. The powder was pressed into rhombic shape and sintered at 1600°C at 4 hours soaking time to yield dense body. To study the effect of the phase transformation of the fabricated tool, machining was performed on the stainless steel 316L at 2000 rpm cutting speed. XRD analysis were performed on three type of ZTA-MgO samples which were the raw powder, the sintered samples and also the samples after machining process. Results shows that the m-ZrO₂ reduced to 0% when sintering process take place and reappear at 12% when the machining process take place proving the occurrence of transformation toughening during the machining process. The consequence of this condition is the hardness of the samples increased by 22% while the fracture toughness decreased by 21.1%.

Abstract: A Si₃N₄ ceramic tool material with high mechanical properties was fabricated by hot-pressing sintering process. The high speed machining of Inconel 718 tests were carried out with round ceramic inserts. The failure surface and microstructure were analyzed by scanning electron microscopy (SEM) to reveal the ceramic tool failure mechanisms. The results showed that the main failure mechanisms of the Si₃N₄ ceramic tool were flaking, micro-chipping, abrasive wear and adhesive wear in the turning process. On the other hand, chipping, flaking and adhesive wear were the main failure reasons in the milling process. Meanwhile, some small flaking along the cutting edge and step-shaped flaking on the rake face closed to the cutting edge were found on the failure surfaces, which was a typical self-sharpening failure characteristic of the ceramic tool in the high-speed cutting process. This tool failure evolution characteristic of the ceramic tool can be attributed to its higher flexural strength and fracture toughness, which was beneficial to improve the tool life and was constrained by cutting conditions.

Abstract: The purpose of this research is to find the effects of cutting speed on the performance of the ZTA ceramic cutting tool. Three types of ZTA tools used in this study which are ZTA-MgO(micro), ZTA-MgO(nano) and ZTA-MgO-CeO₂. Each of them were fabricated by wet mixing the materials, then dried at 100°C before crushed into powder. The powder was pressed into rhombic shape and sintered at 1600°C at 4 hours soaking time to yield dense body. To study the effect of the cutting speed on fabricated tool, machining was performed on the stainless steel 316L at 1500 to 2000 rpm cutting speed. Surface roughness of workpiece was measured and the tool wears were analysed by using optical microscope and Matlab programming where two types of wear measured i.e. nose wear and crater wear. Result shows that by increasing the cutting speed, the nose wear and crater wear increased due to high abrasion. However, surface roughness decreased due to temperature rise causing easier chip formation leaving a good quality surface although the tool wear is increased.

Abstract: The machining of titanium alloys is challenging in every aspect. In order to avoid waste material by cutting processes and to improve mechanical properties, forming processes offer many advantages but harbor also challenges. To face these challenges, especially techniques like isothermal forging are promising methods. Isothermal forging is an appropriate process for achieving a microstructure with excellent properties for high performance applications in aviation technology and turbine construction. One of the main challenges in this special process is the determination of a tool material with a high temperature resistance as well as a high resistance against the work load of forging processes. Given their high hardness, temperature resistance and wear resistance, technical ceramics feature properties classifying them as generally suitable for this application. This article deals with the complete design of an isothermal forging process with ceramic tool material for titanium forming. The material characterization of the forming material by flow curve determination is performed to receive data for FE analyses. Afterwards, a ceramic tool system for isothermal forging is designed and manufactured. The tests show that especially the brittleness of technical ceramics restricts their application as tool material for isothermal titanium forming. Additional investigations on isothermal forging using carbide metal as tool material show the benefit of isothermal titanium forging. The results of metallographic analyses are given.

Abstract: TiB₂/WC/h-BN micro-nano composite gradient self-lubricating ceramic tool material was prepared by vacuum hot-pressing technique. The mechanical properties were tested and compared. The best flexural strength, fracture toughness and Vickers hardness of the tool material were 678MPa, 4.75MPa·m^1/2 and 15.1GPa, respectively. The microstructure was analyzed by thermal field emission scanning electron microscope (SEM). TiB₂ nanoparticles were obviously observed in the ceramic matrix. It suggested that the developed TiB₂/WC/h-BN micro-nano composite gradient self-lubricating ceramic tool materials will have potential application in dry machining.

Abstract: The introduction and application of common finite element method (FEM) about the modern metal cutting theory research was stated emphatically. Graded self-lubricating ceramic tool materials was briefly introduced, and problems existed about simulating the metal cutting process using FEM are pointed out and discussed in this study.

Abstract: This study deals with the cutting performance of ceramic tools in turning of mild steel and BN free-machining steel based on it. The tool lives of ceramic tools in turning standard steel were less than 15 min at the cutting speed 250 m/min. On the other hand, the tool lives in turning of BN free-machining steel were obvious longer than that of standard steel. The tool life of TiC added alumina ceramic tool reached almost 10 hours in the case that the tool life criteria was set at VB=0.3mm. This tool life was twice as long as that of coated carbide tool.

Abstract: Alumina ceramic tools have played an important role in metal working industry as mainly applied ceramic tool materials. They have already become modern ceramic materials with better physical properties and cutting performances. The sorts and developing status of alumina ceramic tools are introduced here. The cutting performances and applications are elaborated. Furthermore, the matching issues are analyzed between alumina ceramic tool and its cutting object.