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Research on Tool Life of Coated Cemented Carbide Inserts for Milling AISI410 Stainless Steel
ABSTRACT AISI410 stainless steel is widely applied in the manufacture of many kinds of commercial units, such as steam turbine blades, mechanical parts of pump and steam generating installations, etc. In the processing there are many problems including low thermal conductivity, serious work hardening and big cutting force. AISI410 stainless steel belongs to the typical difficult-to-machine material. A series of orthogonal steel tests about milling AISI410 stainless with coated cemented carbide inserts were carried out. The regularity of the tool life based on the orthogonal milling experiment was investigated, the tool life model was proposed, and the independent effect of each factor of the model was analyzed. The results show that the influences on the tool life of milling method, feed per tooth, cutting speed and cutting depth for milling AISI410 stainless steel reduce in turn. The influence of feed per tooth on tool life increases with the lowering of cutting speed. In the constant cutting efficiency condition, lowering cutting speed and increasing the amount of feed per tooth are the better selection for a longer tool life.
KEY WORDS milling method; coated cemented carbide inserts; tool life model; stainless steel;
Numerical Simulation of Surface Coating's Effect on Cutting Process
ABSTRACT In the paper, the effect of the coating of cemented carbide insert on cutting process was researched by simulation using the finite element method. The results show that the TiC coating on the cemented carbide can reduce the c utting force by an average of 19.7%, of which the main cutting force is decreased by 15.7%, which can help enhancing the durability of the insert and reducing output powder of the machine. Moreover, the axial force and the radial force are decreased by 19.4% and 23.6%, respectively, which can help improving the machining accuracy and surface quality. During cutting, there exists intensive isotherm distributions on the insert surface with a coating and the maximum temperature is 907 °C, while scattered isotherm distributions on the common insert surface with the maximum temperature being 882 °C, which is relevant with low thermal conductivity of the coating. In addition, the highest surface temperature is not distributed at the cutting edge, but at the root during cutting. Meanwhile, the results of the simulation and experiment were compared. The average errors for the axial force, main cutting force and radial force are 7.9%, 3.8%, 7.3%, respectively, which indicates that the errors are not large.
KEY WORDS coating; simulation; cutting force; surface temperature
Study on Preparation of Cemented Carbide Coating by 45 # Steel Surface Sintering
Surface treatment technology is to improve the surface performance, improve the service life of mechanical parts of an effective measure, has been widely used. The main processes for preparing surface coating or coating are chemical vapor deposition, physical vapor deposition, laser cladding, thermal spraying, sol-gel, self-propagating high-temperature synthesis. These methods have their own characteristics, they exist in the main problem is the thickness of the coating or coating thinner, and the interface with the substrate instability, combined strength is low, equipment investment, process complexity. Powder metallurgy preparation of surface hard alloy coating can solve these problems to a certain extent.
Carbide has a high hardness, abrasion resistance, elastic modulus, compressive strength and stable chemical properties, especially the high temperature strength, making it in modern tool materials, wear-resistant materials, high temperature and corrosion resistance Materials and other aspects of the important position, the application is more and more widely. The sintered hard alloy coating on the surface of ordinary 45 steel was carried out by powder sintering method, and the process and structure of the surface cemented carbide were analyzed.
2 Selection of Cemented Carbide Cladding Materials The requirement for cemented carbide cladding materials is to form a interface with a higher bonding strength to the matrix material. Kerans and other W will be divided into the interface of the sudden deformation, compound type and diffusion of three, in terms of WC cemented carbide, it and 45 steel matrix can only produce diffusion between the interface, if the coating material contains iron, 45 steel between the proliferation of the formation of metallurgical interface. Therefore, FeCNi alloy containing iron as the main component is selected as the binder.
Iron, cobalt and nickel are the first group of elements, used alone as a cemented carbide binder when the best cobalt, nickel, iron is the worst, mainly iron easy to form such as W3Fe3C class brittle compounds, so that the brittle alloy Increased, reduced strength, but also hinder the alloy sintering and bonding. However, iron can be improved by adding appropriate alloying elements such as cobalt and nickel, and the improved binder can be enhanced by martensitic transformation, precipitation hardening and disorder-ordered transformation. For WC-Fe / Ni / Co based cemented carbide, when the mass ratio of iron to nickel + cobalt is greater than 1, the hardness of the material is the highest, the bonding phase is martensite or martensite + retained austenite The The use of FVONi as a binder to completely wet the hard phase WC, with a lower melting point, easy to melt at a much lower temperature than the WC sintering, at the same time, WC in which a certain degree of solubility, easy to form brittle Three-phase, can get martensite, when the bond phase of the mass fraction (the same below) to 20%, the mechanical properties and WC-Co carbide equivalent.
3 Sample preparation and test method The composition of the cemented carbide powder for the test was 82% WC, 18% FeQrNi alloy (65 g, 20% 0, 15%); the base material was 45 steel. The powder was mixed with a KQM-X4 ball mill for 30 h and then triturated with water glass and coated on the surface of the sample and dried by vacuum at 80 ° C. In the IVNi-CW-C cemented carbide, the content of the binder phase is 10% and the cobalt-nickel mass ratio is 1: 1, the eutectic temperature is about 1300 ° C, and vacuum sintering is selected at 12001400X: different temperatures And the sintering time was 30 min.The phase composition of the coating was analyzed by D / max-3A X-ray diffractometer. The element distribution in the coating was analyzed by CXA-733 electron probe, and the coating was measured by HVSIOOO microhardness tester The hardness distribution of the section.
4 test results and discussion 4.1 sintering temperature on the impact of coating structure 280X: when the coating cracks, and the matrix can not generate a solid interface, easy to peel off. When the sintering temperature exceeds 1350 ° C, the number of liquid phases in the coating process increases during the sintering process, which causes the coating to be lost, so that the hard phase can not be evenly distributed in the cladding layer, and the hard phase gathers more seriously and can not form a complete coating Floor.
2801300 ° C sintering, the coating of the organization consists of three parts, namely the coating area, the transition zone and the matrix. The hard-point WCs are evenly distributed in the cladding, and the hard phases are closely connected by the bonding phase. The cladding layer is firmly bonded together through the transition layer and the matrix. The whole coating structure is dense and the grains are small and no pores , Cracks and other defects. 320C, the surface of the coating to form carbide, carbide form see, clearly visible bond phase needle-like martensite. In the sintering, the main composition of the cladding is the addition of the carbide phase (FtNiG), which is mainly composed of a-Fe / Co / Ni, hard phase WC and precipitated phase Co3W3C at 1320 ° C sintering. The generation of carbides can increase the brittleness of the material and adversely affect the wear resistance of the coating, so the choice of sintering temperature should avoid the formation of carbide phases in the cladding.
4.2 The microhardness of the coating with microhardness is about 850HV, and the microhardness in the transition zone decreases gradually. In the cladding, a large amount of WC hard spots have high hardness. During the sintering process, the binder phase forms a liquid phase, and the WC particles are displaced under the action of the liquid surface tension, and the coating begins to densify, and the surface of the particles The atoms gradually dissolved in the liquid phase, due to the movement, the particles began to move closer, contact, the formation of a solid solid phase skeleton, the remaining liquid phase filled in the gap between the skeleton and empty. The atoms on the surface of the particle phase are gradually dissolved in the liquid phase, so that the tungsten content in the binder phase is remarkably increased, while the partially dissolved WC is dispersed in the cladding in the form of the second phase, which obviously improves the bonding phase Microhardness, in addition, the dispersed phase of the dispersed carbide phase Co3W3C in the cladding layer also increases the hardness of the binder phase. The transition zone is formed by the diffusion of elements between the cladding and the matrix. Due to the limited diffusion ability of WC, the content of the matrix in the transition zone is gradually reduced, and the results of the electron probe analysis are shown in Fig.
The microstructures of the cladding sections are dense, the structure is uniform and the diffusion is permeated with the matrix, and the bonding is strong, no pores and cracks.
The distribution of the hard phase and the distribution of the particles in the cladding, the dissolution and diffusion of the particle phase in the cladding, and the generation of the new phase. The structure of the bonded phase is martensite.
Powder metallurgy has an irreplaceable position in the parts manufacturing industry
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