The cutting performance of Al2O3 and Si3N4 ceramic cutting tools in the milling plywood

ABSTRACT

This research focuses on the cutting performance of Al₂O₃ and Si₃N₄ ceramic cutting tools in up-milling plywood, the results of which are as follows. First, whether the tool material is Al₂O₃ or Si₃N₄ ceramic, the cutting forces at low-speed cutting were less than those at high-speed cutting, and the machining quality at low-speed cutting was greater than that at high-speed cutting. Then, whether at low- or high-speed cutting, the cutting forces of Al₂O₃ cutting tools were higher than those of Si₃N₄ cutting tools, and the machining quality of plywood milled by Al₂O₃ ceramic cutting tools was poorer than that milled by Si₃N₄ ceramic cutting tools. Finally, Si₃N₄ ceramic cutting tools were more suitable to machine the wooden productions with much glue content than Al₂O₃ ceramic cutting tools for the better machined quality.     

High-entropy carbide-based ceramic cutting tools

In this study, a novel high-entropy carbide-based ceramic cutting tool was developed. The cutting performance of three kinds of high-entropy carbide-based ceramic tools with different mechanical properties for the ISO C45E4 steel were evaluated. Although the pure (Ti_0.2Zr_0.2Nb_0.2Ta_0.2Mo_0.2)C_0.8 ceramic cutting tool exhibited the highest hardness of 25.06 ± 0.32 GPa, the cutting performance was poor due to the chipping and catastrophic failure caused by the low toughness (2.25 ± 0.27 MPa m^1/2). The (Ti_0.2Zr_0.2Nb_0.2Ta_0.2Mo_0.2)C_0.8–15 vol% cobalt cutting tool with highest fracture toughness (6.37 ± 0.24 MPa m^1/2) and lowest hardness (17.29 ± 0.79 GPa) showed the medium cutting performance due to the low wear resistance caused by the low hardness. The (Ti_0.2Zr_0.2Nb_0.2Ta_0.2Mo_0.2)C_0.8–7.7 vol% cobalt cutting tool showed the longest effective cutting life of ∼67 min due to the high wear resistance and chipping resistance caused by the high hardness (21.05 ± 0.72 GPa), high toughness (5.35 ± 0.51 MPa m^1/2), and fine grain size (0.60 ± 0.15 μm). The wear mechanisms of the cobalt-containing (Ti_0.2Zr_0.2Nb_0.2Ta_0.2Mo_0.2)C_0.8 ceramic cutting tools included adhesive wear and abrasive wear and oxidative wear. This research indicated that the high-entropy carbide-based ceramics with high hardness and high toughness have potential use in the field of cutting tool application.     

Preparation and mechanical properties of Si3N4 nanocomposites reinforced by Si3N4@rGO particles

A new type of reduced graphene oxide-encapsulated silicon nitride (Si₃N₄@rGO) particle was synthesized via an electrostatic interaction between amino-functionalized Si₃N₄ particles and graphene oxide (GO). Subsequently, the Si₃N₄@rGO particles were incorporated into a Si₃N₄ matrix as a reinforcing phase to prepare nanocomposites, and their influence on the microstructure and mechanical properties of the Si₃N₄ ceramics was investigated in detail. The microstructure analysis showed that the rGO sheets were uniformly distributed throughout the matrix and firmly bonded to the Si₃N₄ grains to form a three-dimensional carbon network structure. This unique structure effectively increased the contact area and load transfer efficiency between the rGO sheets and the matrix, which in turn had a significant impact on the mechanical properties of the nanocomposites. The results showed that the nanocomposites with 2.25 wt.% rGO sheets exhibited mechanical properties that were superior to monolithic Si₃N₄; the flexural strength increased by 83.5% and reached a maximum value of 1116.4 MPa, and the fracture toughness increased by 67.7% to 10.35 MPa·m^1/2.     

新型双马来酞亚胺树脂/纳米Si3N4复合材料的性能

研究了一种新型的双马来酞亚胺树脂-5406树脂及其纳米Si3N4复合材料的性能。结果表明:5406树脂不仅具有很高模量,耐热性好,而且豁度很低,有利于纳米粒子的分散和纳米复合材料浇铸成型;纳米Si3N4粒子的填充可明显改善5406树脂的摩擦磨损性能。扫描电镜显示5406树脂主要发生的是塑性变形,5406树脂助米Si3N4复合材料主要是钻着磨损。     

Preparation of Si3N4 ceramic based on digital light processing 3D printing and precursor infiltration and pyrolysis

The emergence of digital light processing (DLP) 3D printing technology creates favorable conditions for the preparation of complex structure silicon nitride (Si₃N₄) ceramics. However, the introduction of photosensitive resin also makes the Si₃N₄ ceramics prepared by 3D printing have low density and poor mechanical properties. In this study, high-density Si₃N₄ ceramics were prepared at low temperatures by combining DLP 3D printing with precursor infiltration and pyrolysis (PIP). The Si₃N₄ photocurable slurry with high solid content and high stability was prepared based on the optimal design of slurry components. Si₃N₄ green parts were successfully printed and formed by setting appropriate printing parameters. The debinding process of printed green parts was further studied, and the results showed that samples without defects and obvious deformation can be obtained by setting the heating rate at .1°C/min. The effect of the PIP cycle on the microstructure and mechanical properties of the Si₃N₄ ceramics was studied. The experimental results showed that the mass change and open porosity of the samples tended to be stable after eight PIP cycles, and the open porosity, density, and bending strength of the Si₃N₄ ceramics were 1.30% (reduced by 97%), 2.64 g/cm³ (increased by 43.5%), and 162.35 MPa.     

Enhanced thermal conductivity in Si3N4 ceramic with the addition of Y2Si4N6C

Si₃N₄ ceramic was densified at 1900°C for 12 hours under 1 MPa nitrogen pressure, using MgO and self‐synthesized Y₂Si₄N₆C as sintering aids. The microstructures and thermal conductivity of as‐sintered bulk were systematically investigated, in comparison to the counterpart doped with Y₂O₃‐MgO additives. Y₂Si₄N₆C addition induced a higher nitrogen/oxygen atomic ratio in the secondary phase by introducing nitrogen and promoting the elimination of SiO₂, resulting in enlarged grains, reduced lattice oxygen content, increased Si₃N₄‐Si₃N₄ contiguity and more crystallized intergranular phase in the densified Si₃N₄ specimen. Consequently, the substitution of Y₂O₃ by Y₂Si₄N₆C led to a great increase in ~30.4% in thermal conductivity from 92 to 120 W m^?1 K^?1 for Si₃N₄ ceramic.     

Cutting performance and wear mechanism of honeycomb ceramic tools in interrupted cutting of nickel-based superalloys

Nickel-based superalloys are favored because of high fatigue strength, corrosion resistance and oxidation resistance. However, the characteristics of high hardness, poor heat dissipation and sticking make the machinability of nickel-based superalloys poor, which is more serious for interrupted processing. Therefore, honeycomb ceramic tools are utilized to turn GH4169. Cutting and impact force, wear patterns and mechanism of honeycomb ceramic tools are analyzed. The results demonstrate that the impact force is greater than the average cutting force. Fractures, chipping and adhesion are the main wear characteristics of honeycomb ceramic tools. Furthermore, adhesive, abrasive and diffusion wear are the main wear mechanisms.     

Finite element simulation and experimental analysis of B4C-TiB2-SiC ceramic cutting tools

Here, cutting properties and wear mechanism of the home-made B₄C-TiB₂-SiC ceramic cutting tools in turning of AISI 4340 steel workpieces were studied through a combination of finite element simulation using Deform-3D software and turning experiments. Simulation results show that cutting parameters have significant effects on the main cutting force and tool temperature of the B₄C-TiB₂-SiC cutting tool. The optimal cutting parameters for the ceramic cutting tool are cutting speed of 300 m/min, depth of cut of .3 mm, and feed rate of .1 mm/r. Experimental results show the cutting length of the B₄C-TiB₂-SiC cutting tool is about 101 m, which is 21.0% and 32.9% larger than that of the home-made B₄C-TiB₂ ceramic cutting tool and commercially available tungsten carbide tool, indicating that the B₄C-TiB₂-SiC cutting tool has a desired service life. The surface roughness of the workpieces processed by the B₄C-TiB₂-SiC cutting tool is 2.43 µm, which is 29.4% lower than that of the workpieces processed by the B₄C-TiB₂ cutting tool, indicating that the B₄C-TiB₂-SiC cutting tool has a satisfying machining accuracy. Wear forms of the B₄C-TiB₂-SiC ceramic cutting tool involve craters, chipping, and flank wear, and the main wear mechanisms are abrasive, adhesive, oxidative, and diffusion wear.     

In situ synthesis of cobalt silicide particle reinforcing and coloring Si3N4 ceramics

In this paper, silicon nitride (Si₃N₄) ceramics with black color and high toughness were fabricated by gas pressure sintering and characterized by X-ray diffraction, Raman, scanning electron microscopy, EDS, and transmission electron microscopy. The in situ formed cobalt silicide was confirmed to contribute to the black color through the introduction of CoO. Due to the addition of CoO, the growth of β-Si₃N₄ grains is promoted, forming elongated grains, and eventually forms the self-reinforcing microstructure. However, with adding excessive CoO, interfacial debonding is found between cobalt silicide and Si₃N₄ matrix and a decrease in strength was resulted. The optimum composition is 1 mol% CoO in Si₃N₄, with the fracture toughness of 9.9 ± 0.3 MPa m^1/2, flexural strength of 826.1 ± 46.0 MPa, and a much darker black color. The mechanism of color formation is discussed where the black color derives mainly from the metallic silicon and additionally the porosity.     

Colored Si3N4 ceramics via constructing Nd3+ doped core-shell structures

Si₃N₄ ceramics have been attractive casing materials for electronics devices under the 5th generation mobile communication technology because of its outstanding comprehensive properties. However, single color cannot meet the needs of most consumers. Here, a typical strategy, involving forming core-shell structures by utilizing Nd₂O₃-MgO-YAG system, is proposed to rich color. Scanning transmission electron microscope-energy dispersive X-ray spectrometry results confirm the presence of core-shell structures in the silicon nitride matrix, and the core is pore and the shell is Nd-enriched liquid phase. The Nd-rich core-shell structure as the color center makes the silicon nitride appear cyan or blue.     

Temperature-driven wear behavior of Si3N4-based ceramic reinforced by in situ formed TiC0.3N0.7 particles

Si₃N₄ as a structural ceramic is desirable for applications in spacecraft, transportation, and energy, but its poor high-temperature properties still do not satisfy the actual requirements. Here, a TiC_0.3N_0.7 reinforced Si₃N₄ ceramic is successfully designed and fabricated via the high-temperature nitridation of TiC_x. It is found that TiC_0.3N_0.7 grains with the size of 1-2 μm are uniformly dispersed in the Si₃N₄ matrix and show a firm bond with substrate. Compared with pure Si₃N₄, the doping of harder TiCN phase can effectively improve ceramic's hardness and fracture toughness at a certain temperature. Importantly, the ceramic material displays extraordinary wear resistance across a wide temperature range (eg, the wear rate of TiC_0.3N_0.7 containing Si₃N₄ over 63 times and 178 times better than pure Si₃N₄ at 600 and 900°C, respectively). More broadly, a correlation between wear mechanism and temperature is established, and the result shows that the mechanical strength and tribochemical oxidation as two key factors determine the wear behavior of the material. These results developed here can provide a springboard for preparation and optimization of multiphase ceramics that serve under high-temperature conditions.     

Stress distribution around Fe5Si3 and its effect on interface status and mechanical properties of Si3N4 ceramics

Si₃N₄ ceramics with different amount of Fe₅Si₃ were prepared by adding FeSi₂. Residual thermal stress distribution and elastic energy around Fe₅Si₃ particles in various depths were calculated. The interface status between second phase particles and matrix was analyzed in terms of stress and energy. High tangential compressive stresses and low radial tensile stresses were generated along the surface of the ceramics. Elastic strain energy caused by unit interface was high around big particles in deep area of the ceramics. Microcracks are observed around the big Fe₅Si₃ particles. Furthermore, accord to our calculation, microcracks are easily generated around particles in superficial layer of matrix when second phase particles have lower thermal expansion coefficient than the matrix, while microcracks tend to be generated in deep layer of matrix preferentially when the thermal expansion coefficient of second phase particles is higher than matrix. Residual stresses and microcracks around Fe₅Si₃ particles greatly influenced mechanical properties. Fracture toughness of Si₃N₄ ceramics with similar Si₃N₄ particle size distribution increased with the amount of Fe₅Si₃, and fine Fe₅Si₃ particles could enhance the strength of Si₃N₄ ceramics. Si₃N₄ ceramics exceeding 1.2 GPa strength were prepared.     

Texture,microstructures, and mechanical properties of AlN‐based ceramics with Si3N4–Y2O3 additives

Textured AlN‐based ceramics with improved mechanical properties were prepared by hot pressing using Si₃N₄ and Y₂O₃ as additives. The introduction of Si₃N₄–Y₂O₃ into AlN matrix led to the formation of secondary Y₃AlSi₂O₇N₂ and fiber‐like 2H^δ AlN‐polytypoid phases, the partial texture of all crystalline phases, and the fracture mode change from intergranular to transgranular. Consequently, Vickers hardness, fracture toughness and flexural strength of AlN‐based ceramics by the replacement of Y₂O₃ by Si₃N₄–Y₂O₃ increased significantly from 10.4±0.3 GPa, 2.4±0.3 MPa m^½ and 333.3±10.3 MPa to 14.2±0.4 GPa, 3.4±0.1 MPa m^½ and 389.5±45.5 MPa, respectively.     

Temperature-dependent mechanical and oxidation behavior of in situ formed ZrN/ZrO2-containing Si3N4-based composite

In this work, Si₃N₄ and Zr(NO₃)₄ were used as raw materials to prepare ZrN/ZrO₂-containing Si₃N₄-based ceramic composite. The processing, phase composition, and microstructure of the composite were investigated. Hardness and fracture toughness of the ceramics were evaluated via Vickers indentation in Ar at 25°C, 300°C, 600°C, and 900°C. During spark plasma sintering, Zr(NO₃)₄ was transformed into tetragonal ZrO₂, which further reacted with Si₃N₄, resulting in the formation of ZrN. The introduction of ZrN enhanced the high-temperature mechanical properties of the composite, and its hardness and fracture toughness reached 13.4 GPa and 6.1 MPa·m^1/2 at 900°C, respectively. The oxidation experiment was carried out in air at 1000°C, 1300°C, and 1500°C for 5 h. It was shown that high-temperature oxidation promoted the formation and growth of porous oxide layers. The microstructure and phase composition of the formed oxide layers were investigated in detail. Finally, it was identified that the obtained composite exhibited a higher thermal diffusivity than that of monolithic Si₃N₄ in the temperature range of 100°C–1000°C.     

Si3N4/Si3N4扩散连接的力学性能研究

采用热压法进行氮化硅陶瓷材料的扩散连接.结果表明:在1520℃,15MPa,60min条件下,氮化硅连接体的最高强度为448.6MPa,超过母材强度;平均连接强度为401.5MPa,为母材强度的96%.     

氮化硅针状晶体的制备

采用Ｓｉ粉直接氮化的方法制备氮化硅针状晶体,通过热力不计算,选择了晶体 温度和压力范围,探讨了温度、压力、添加剂等对针状晶体晶相、形貌、产率的影响,并在１８５０℃、ＣａＯ质量分数为１０％条件下,制备了长径比为４￣１０的β－Ｓｉ３Ｎ４针状晶体,产率为６８％,采用ＸＲＤ,ＴＥＭ、ＳＥＭ对得到的氮化产物及针状晶体进行了表征。     

Ultrasonic-assisted preparation of complex-shaped ceramic cutting tools by microwave sintering

Complex-shaped ceramic tools were prepared by ultrasonic-assisted molding technology and microwave sintering. A uniaxial ultrasonic vibration compaction system was designed. The effects of ultrasonic vibration and molding pressures on mechanical properties and microstructures of A₂O₃ and Al₂O₃/SiC complex-shaped milling cutters were investigated by simulations and experiments. The results indicated that the density was distributed unevenly within the green ceramic tool samples, especially poor in the tool edges. These drawbacks were well improved by ultrasonic-assisted molding technology and microwave sintering. Applying ultrasonic vibration during the compaction process of green ceramic tool samples could improve the densification, hardness and reduce the randomness of mechanical properties of the sintered ceramic tool materials, especially for the difficult-to-sinter composite ceramics (with poor density). For A₂O₃ ceramic tool, fully dense microstructure was achieved, and for Al₂O₃/SiC ceramic tool, the cutting edges showed better density than that of the interior body, which was beneficial to improve the abrasion resistance of cutting tool.     

The Role of Thermal Shock on Tool Life of Selected Ceramic Cutting Tool Materials

The introduction of Si₃N₄- and Al₂O₃-based tools has greatly increased the speed of metal removal and the productivity of metal-cutting operations. High-speed machining elevates the temperature at the tool/workpiece interface and subjects the tool to considerably higher stress, resulting from increased mechanical forces and thermal gradients. Under these circumstances, the thermal shock resistance of tool materials would be expected to play a more important role in determining the tool life and should be more prominently considered in both material design and applications. It was of interest to devise a series of controlled thermal shock machining tests and to assess the modes of ceramic cutting-tool wear. The resistance of ceramic cutting-tool materials to wear or fracture under these conditions is discussed in terms of thermal shock parameters.     

Si3N4对硫系玻璃的热学和力学性质的影响

对在两个硫系玻璃系统中引入Si3N4所产生的效应进行了研究,发现其影响程度与基玻璃的组成有关。用描述共价键固体交连程度的系统平均配位数概念讨论了这种关系。发现与处于富硫族元素组成区的硫系玻璃相比,在处于富阳性元素组成区的硫系玻璃中引入Si3N4对玻璃热、力学性能的改善程度较低。这是因为没有足够的硫族元素起连接作用,多余的Si并不能对网络交连程度的提高做贡献。进一步的研究结果证实了在不同组成区引入Si3N4对玻璃转变温度θg的不同影响。在富阳性元素组成区θg甚至随系统平均配位数的增加而略有提高的原因则在于“错键效应”对玻璃网络所可能起到的局部连接作用。