| In modern machining, the ceramic material with excellent heat resistance, wear resistance and chemical stability play an increasingly important role in the field of high-speed cutting and cutting hard materials aspects; but its drawback is the low flexural strength and brittle. With the development of high-speed dry cutting technology Hard, especially cutting continues to improve, more and more tools for high performance requirements, which requires ceramic tool fracture toughness and strength to be higher. In the field of high-speed cutting, Micron ceramic tool has incomparable advantages than hard carbide cutting tool materials, but the disadvantage is the low flexural strength and brittleness, to a large extent restricted its scope of application. Nano-composites with high flexural strength and fracture toughness, can be used as a high cutting tool materials.This article was prepared nanoscale solid lubricant CaF2, Al2O3-TiN-CaF2 nano-composite ceramic cutting tools using sub-micron Al2O3 as the matrix material, sub-micron TiN as toughening phase, nano-sized CaF2 as solid lubricant additives, by vacuum hot-pressing technique. and test the mechanical properties and wear characteristics of the standard sample. The paper includes the following sections:(1) Contrast composite ceramic materials toughened material physical and chemical properties, choose the most suitable for producing fusion cutting and wear TiN as toughening Al2O3 matrix composites with ceramic material, improve the overall performance of the composite ceramic material, making it more suitable for high-speed and high-speed dry cutting hard cutting.(2) In regard to self-lubricating composite ceramic cutting tools under study with the premise of a solid lubricant, comparison of various solid lubricants (CaF2, BaF2, MoS2, WuS2, soft metals Ag/Cu, precious metals Au, Cr, graphite, etc.) physical properties, self-lubricating properties and chemical properties, we chose CaF2 as a solid lubricant additive of composite tool.(3) Based on in-depth exploration of chemical reactions precipitated powder synthesis method, we determined that calcium nitrate and ammonium fluoride as the raw material, complex solution of distilled water and ethanol as the solvent polyethylene glycol (PEG) 6000 as a dispersant prepared using new technology and methods to prepared nano-sized CaF2 powder, and powder was analyzed by the observations of thermal field scanning electron microscopy (SEM) and X-ray diffraction (XRD) and energy dispersive spectrometry(EDS).(4) According to the study on ceramic composite technology tools by vacuum hot-pressing technique, experimentally determined suitable for this task sintering parameters:sintering pressure 32MPa, the sintering temperature is 1550℃, holding dwell time of 20 minutes; raw material composition volume fraction:submicron Al2O3 62.5%,22.5% submicron TiN,10% of nano-sized CaF2; various sintering additive:Mo is 1%,Ni of 3%,MgO 1%.(5) The sintered blank according to the flexural strength and friction and wear testing requirements of a standard sample preparation. Sample bending strength, hardness and fracture toughness were 615MPa,11.8GPa and 3.6MPa · m1/2, the friction coefficient of 0.3 magnitude grated rate is 10-15 m3/N·m. Mechanical properties and other self-lubricating composite material similar tool, but its friction and wear properties superior to other self-lubricating composite tool materials.(6) Compared to the mechanical properties and friction and wear characteristics of the composite ceramic tool, we reveal toughening mechanism of self-lubricating composite ceramic tool and friction reduction mechanism. |
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