Brief introduction of special ceramic tool materials (2)

4. Alumina-carbide cermet cutter: It is made of Al2O3-TiC ceramic material, which uses MO, Ni (or CO, W) and other metals as the ceramic tool material which is hot pressed by the binder phase. Due to the skeleton of the metal-bonded Al2O3 grains and the carbide grains interpenetrating each other, the joint strength is high, so that good cutting performance is formed. These ceramic tools are best suited for the processing of hardened steel, alloy steel, manganese steel, chilled cast iron, cast steel, nickel-based or chromium alloys, nickel-based and cobalt-based funds. It can also be used for cutting non-metallic materials such as fiberglass, plastic sandwich and ceramic materials. Since alumina-carbide cermet has good thermal shock resistance, it can be used for milling, planing, repeated short cutting or other intermittent cutting, and can also be used for wet cutting with cutting fluid.

5. Alumina-nitride cermet: The basic properties and processing range of this ceramic tool material are comparable to those of Al2O3-carbide cermet material, but it has better thermal shock resistance due to the substitution of carbide for nitride. And more suitable for new cutting. However, its flexural strength and hardness are lower than those of TiC-added cermets, and its research and in-depth development are still continuing.

6. Boron Nitride Ceramic Cutter: Recently, Sumitomo Electric Co., Ltd. developed a ceramic tool material with higher hardness—adhesive cubic boron nitride ceramic (CBN) sintered body. The sintered material is prepared by sintering at a pressure of 7 to 80 Pa at an ultrahigh temperature and high pressure of 2,300 to 2,400 ° C for 10 minutes. This technology also includes unique software technologies such as grinding fine powder diameters to improve CBN purity during the raw material preparation stage. A sintered boron nitride ceramic material having a CBN content of 100% is developed by combining fine particles having a particle diameter of 0.5 mm or less.

Ceramic tools made of boron nitride material do not suffer from common thermal cracking and chipping at the tip end of the tool when cutting hard steel with very high hardness. According to different conditions, the use time of boron nitride ceramic tools can be extended by more than 10 times compared with CBN sintered bodies containing other bonding materials, and it can be used as a material for interrupted cutting. Especially in the automotive industry, hBN sintered bodies are widely used in machining as cutting materials for machining hard cast iron materials such as engines.

Since the prior sintered body contains a particulate binder, it cannot form a unique property such as hardness and thermal conductivity as high as CBN. For example, CBN direct conversion technology is not suitable for high-speed cutting tools because its granularity is too coarse.

7, silicon nitride ceramic tools: silicon nitride ceramic tools have low density, high strength, high hardness physical properties. Its room temperature hardness value has exceeded the hardness of the best cemented carbide tool, which greatly improves its cutting ability and wear resistance, and can process all kinds of hard steel and hardened cast iron with high hardness. Its flexural strength has exceeded that of high-speed and is comparable to ordinary cemented carbide. The fracture toughness value of silicon nitride ceramic tools is 6~7mpaVm better than other series of tools. The thermal resistance index of silicon nitride ceramic tools is as high as 600-800 °C, which is obviously superior to other series of ceramic tools (300-400 °C), and its cutting speed is also 3 to 10 times higher than that of cemented carbide tools. Therefore, in the processing of high-strength intermittent parts, it shows its superior performance.

Silicon nitride ceramic tools include: pure silicon nitride ceramic tools and silicon nitride composite ceramic tools.

1 pure silicon nitride ceramic cutter, its hardness HRA91～92, bending strength 700～900Mpa, fracture toughness 4.2～5.2MpaVm, heat resistance up to 1300～1400°C, its thermal expansion coefficient is 3.0×10-6/°C, Has good antioxidant properties. 2 silicon nitride composite ceramic cutter; it is a ceramic tool made by adding a composition of Al2O3, Y2O3, TiC, TiN and MgO to a silicon nitride matrix, and using a composite strengthening effect and cold pressing sintering, the performance of which is superior to that of hot pressing. Pure silicon nitride ceramic tool.

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