November 27, 2019
Wear behaviors and lubrication medium of TiC/Al2O3 ceramic wire drawing dies
The suitable test equipment for wire-drawing was designed. Wire-drawing tests were carried on with this equipment for TiC/Al2O3 ceramic wire drawing dies. Effect of lubrication medium and drawing velocity on the drawing force was investigated. The wear mechanisms of the ceramic drawing dies were investigated. Worn bore surfaces of the ceramic drawing dies were examined by scanning electron microscopy. The results show that lubricant media have great influence on the drawing force. The drawing force is the smallest when a grease lubricant is used. But alteration of drawing velocity has scarcely any influence on the drawing force. Detailed observations and analyses of the die wear surface reveal that the most common failure of the ceramic drawing die is the wear in the invariable zone and bearing zone owing to the greater press stresses. Abrasive and adhesive wear are found to be the predominant wear mechanisms for ceramic drawing die.
The Al2O3/TiC/Mo/Ni ceramic drawing die was developed by hot pressing sintering technology. The dry friction and wear properties of Al2O3/TiC/Mo/Ni ceramic drawing die materials and 45# steel under different loads and sliding speeds were studied on mrh-3 high-speed ring and block wear tester, and the wear rate was analyzed. The stress distribution of the drawing die of Al2O3/TiC/Mo/Ni ceramics was analyzed by finite element method. The results showed that the Al2O3/TiC/Mo/Ni ceramic drawing mold had good strength and hardness, good wear resistance at high speed, and low wear rate, maintained at 3.1×10-9cm3/(N·m). The wear of the inner hole is the most serious in the working area and the sizing area, mainly abrasive wear, and there is slight fracturing in the exit area.
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November 20, 2019
cemented carbide tool for GH4169 under different cutting distance
The new technology of ion source enhanced multi arc ion plating was used to prepare the gradient coating of alcrtisin with different gradient structure of Si layer on the surface of cemented carbide tools. The microstructure, residual stress, bonding strength, friction and wear of the coating, as well as the properties of milling and drilling gray cast iron were studied in detail. The results show that the alcrtisin coating with different Si layer gradient structure is mainly composed of (al, Cr) n, (al, Ti) n phase and amorphous Si3N4 phase. Among them, the G3 (gradient 3) coating with the most gentle gradient change of Si layer has higher bonding strength, lower residual compressive stress, friction coefficient and wear rate. Milling and drilling experiments show that the main wear mechanisms of coated tools are abrasive wear and adhesive wear. G3 coating reduces abrasive wear and has the highest milling and drilling life, which is mainly due to its gradient design with Si layer, appropriate compressive stress (- 3.8 GPA) and good film-based bonding strength. The results show that the cutting performance of the coated tool can be significantly improved by gradient design of Si layer.
In order to explore the wear law, cutting force and surface roughness of GH4169 processed by cemented carbide tools with different cutting distances, cutting tests were carried out on GH4169 materials. The evolution of carbide tool wear and its effect on cutting force and surface roughness are analyzed. The results show that with the increase of cutting distance, the wear area of the front cutter surface gradually expands, the wear forms of the front cutter surface are coating off, groove wear and adhesion wear, while the wear forms of the back cutter surface are coating off and micro-chip edge. The main reason for the wear of the front tool surface is that there are many hard particles and their strong viscosity in the superalloy materials. The overall variation trend of Fx, Fy and Fz is that the surface roughness first increases and then decreases with the increase of cutting distance, and the surface roughness of the specimen first decreases and then increases with the increase of cutting distance. When the cutting distance is 75m, the surface roughness is the smallest.
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November 13, 2019
properties of spheroidal cast tungsten carbide powder
A super-high temperature furnace was developed to fabricate spheroidal cast tungsten carbide powder with excellent flowability and fine feathery structure in a large scale. Optical microscope and scanning electron microscope were taken to characterize the morphology and microstructure of cast tungsten carbide powder. X-ray diffractometry was used to analyze the phase composition of powders involved. It is found that the carbon potential in the furnace and feeding speed play an important role on the microstructure, morphology and properties of the spheroidal cast tungsten carbide powder. As carbon potential is between 0.3% and 0.9% in the furnace, cast tungsten carbide powder with hardness over 2800(HV0.5), flowability over 7.1s/50g and tap density over 10.3g/cm3 is obtained.
Hard surface technology is of great significance to promote sustainable economic development and build an economical society. Forming hard wear layer on metal/alloy surface with hard surface technology can significantly improve workpiece life and save resources. Due to its high hardness, high abrasion resistance and corrosion resistance, tungsten carbide casting is one of the most widely used hard surface materials. The surface morphology, microstructure and particle size of cast tungsten carbide have a decisive effect on its application. The spheroidal _ fast cooling treatment of traditional cast tungsten carbide powder can significantly improve the toughness of hard surface materials containing cast tungsten carbide, and achieve the best combination of high abrasion resistance and high toughness of hard surface materials. At present, the most representative company in the world that can prepare spherical casting tungsten carbide powder on a large scale is Tekna company of Canada. The company USES high temperature plasma technology to prepare spherical casting tungsten carbide powder. Because of the large flow of Ar gas as plasma carrier and protective atmosphere, the production cost is relatively high. The preparation of spherical casting tungsten carbide powder has been reported at home and abroad. The preparation methods of spherical casting tungsten carbide powder are mainly divided into three categories, namely, plasma high-temperature technology represented by Tekna company. Liquid direct atomization forming technology (CN1486806), represented by hunan dinglixin material engineering center co., LTD and zigong cemented carbide co., LTD. CN1488463, atomization forming method for producing ball casting tungsten carbide powder, 2004.04.14); High temperature arc melting centrifugal fast cooling technology represented by zhuzhou huayang technology co., LTD and Woka Schweisstechnik GmbH (CN2714579, a spherical amorphous material preparation equipment, 2005.08.03; American patent 5089182, Process of manufacturing
cast tungsten carbide spheres, 1992.02. 1
The preparation method of spherical casting tungsten carbide has some problems, such as large gas consumption, poor stability of spherical degree control due to strong impact of airflow in the pellet forming process. In addition, the above technologies also have problems such as wide particle size distribution of spheroidized powder, relatively poor controllability of particle size distribution, poor stability of preparation process, low production capacity and high maintenance cost of equipment.
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November 04, 2019
Production method of spherical thermal spraying powder based on tungsten carbide
The invention belongs to the production method of tungsten carbide based spherical thermal spraying powder in the production of hard alloy. Including WC as the substrate, Co or Co and Cr as the bonding phase, hexane as the ball grinding medium, paraffin as the pellet binder; And through: wet grinding preparation slurry, spray drying granulation, screening dry granule, sintering under the protection of hydrogen, finally sintered powder according to the requirements of classification, so as to obtain the object of spherical thermal spraying powder. The invention has the advantages of short process flow, regular powder morphology and good spherification, and the productivity can be increased by more than 20 times than the background technology, while the equipment investment is only one fourth of the background technology of the same scale. The production cost is low and can carry on the large-scale industrialization production and so on characteristic. It overcomes the disadvantages of large investment of background technology equipment, extremely low productivity, high production cost and can not be used in the production of cemented carbide spherical thermal spraying powder.
Compared with conventional materials, nanomaterials have unique properties in hardness, strength and toughness. The brittleness of nanostructured ceramics is reduced and the toughness is improved. Conventional nanocrystalline powder cannot be directly used for plasma spraying due to its low density, poor fluidity and small mass of individual particles, so it must be reprocessed. This article adopts the ball mill, pulp, spray drying and heat treatment method of Cr2O3 original nano powder together into suitable for thermal spraying with big particle spherical powder, different binder concentrations was studied, powder solids, spray drying conditions and the influence of heat treatment temperature on the physical properties of aggregate powder, measuring the apparent density of aggregate powder, tap density and liquidity, established under the condition of different dry air heating aggregate powder particle morphology of geometric model, discusses the morphology change process during the high temperature heat treatment, The ceramic powder was sprayed on the stainless steel substrate by dc plasma spraying method to prepare Cr2O3 wear-resistant coating. The powder and coating were detected and analyzed by metallographic microscope, scanning electron microscope and X-ray diffraction. The results showed that the size of aggregate powder particles after spray drying.
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