In the cutting process, the cutting force of the cutter is up to 2~3GPa, the cutting temperature is as high as 900~1 100 °C, and the cutting speed is usually in the range of several tens of meters to several hundred meters per minute, so it is under high pressure, high temperature and high speed. The problem of friction and wear of working cutting tools is very serious. Hard coatings play an important role in improving cutting performance and extending tool life. The most studied so far is the TiN coating, which has high hardness, low friction, and good chemical stability. Ti(C, N) coatings have better anti-adhesion and thermal wear resistance than TiN coatings. In addition to having a low coefficient of friction, wear-resistant coatings must also have high microhardness, high toughness, and adhesion to the substrate. By introducing a predetermined number of intermediate transition layers parallel to the substrate, the toughness and hardness of the coated tool can be improved, preventing crack initiation. Studies on TiN multilayer coatings have shown that it has better tribological properties than a single coating. Su et al.'s study of the wear resistance and cutting performance of multi-layered TiN/Ti(C, N) coated tools shows that they have better performance than single layer coatings. The wear resistance and reliability of coatings are often dictated by their mechanical properties. Due to the interaction between the film, interface and substrate, it is difficult to measure the mechanical properties of the coating. The emergence of nano-hardness tester enables people to understand the mechanical properties of coatings in depth from the micro-scale (nano-scale) history. The authors used the nanometer hardness tester to analyze and compare the deformation, failure and wear resistance of the four coatings. 1 Test method Test equipment The test equipment was produced by CSEM Instruments of Switzerland. The system consists of a nanometer hardness tester (NHT) and an atomic force microscope (AFM). It is equipped with optical microscope attachments. The components such as the indenter and the optical microscope for sample selection and observation of the indentation are controlled by an electromechanical positioning system, and the displacement resolution in the vertical force direction is μm. The load is applied to the compression rod by an electromagnetic force generated by an electromagnetic coil mounted on a compression rod supported by a guide spring which is a standard Vickers diamond indenter. Use a capacitive sensor to measure the displacement of the plunger. The overall system load and press-in depth resolutions are 10 μN and 1 nm, respectively. During the loading and unloading process, the sapphire ring, which is always in contact with the surface of the sample to be measured, allows the indenter to precisely position the surface of the sample in a vertical direction. Test samples were prepared on a cemented carbide substrate using CVD techniques TiN, TiN/Ti(C,N)/TiC, TiN/Ti(C,N)/TiC/Ti(C,N)/TiC and TiN/Ti (C , N) / TiC / Ti (C, N) / TiC / Ti (C, N) / TiC and other four wear-resistant coatings. After depositing 99.50% H2, 99.99% N2, 99.99% CH4, 99.50% CO2, chemically pure TiCl4, AlCl3 and other raw materials, the cemented carbide substrate was passivated, cleaned, furnaced, and heated, a CVD coating was deposited and cooled. That is, the sample to be tested is prepared. The thicknesses of the four coatings were 4.0 μm, 1.5 μm/1.0 μm/1.5 μm, 1.5 μm/1.0 μm/1.5 μm/1.0 μm/1.5 μm, and 1.5 μm/1.0 μm/1.0 μm/1.0 μm/1.5 μm/ 1.0 μm/1.5 μm. 2 Test results and discussion Mechanical properties Indentation tests were performed on four kinds of coatings using a nanometer hardness tester to obtain the relationship between load and press-in depth during loading and unloading. E is the elastic modulus and HV is the Vickers hardness value of the coating, which is determined according to Oliver et al. In addition to considering the unloading curve, the method also considers the shape of the indenter and the indentation depth to calculate the contact area under load. Hardness is considered as the average pressure that the material undergoes during unloading. Multilayer coatings have better load carrying capacity than single coatings. Li et al. used a nano-hardness tester to analyze various cracking processes occurring on the coating surface during the indentation process. It was found that the high stress in the contact zone gave rise to the first approximately annular crack penetrating the film around the indenter; The pressure causes the coating/matrix interface to peel off and break off at the contact zone; a second, approximately toroidal, crack or crack chipping through the film layer occurs at the edge of the bent film due to the bending stress. In the first stage, if the coating is cracked in an approximately toroidal penetrating film, a step will appear on the ph curve, otherwise no step will occur. We studied the failure characteristics of the four coatings. It can be seen that as the indentation load increases, a step appears on the ph curve, suggesting that there are several cracks in the coating that form an approximately toroidal penetrating film. Each step corresponds to an approximately toroidal crack in the coating that penetrates through the film, thus defining the load pf at the step as the critical load for failure of the coating. In this way, the critical loads for the fracture failure of the four types of coatings are 11.1 mN, 16.4 mN, 35.5 mN, and 56.3 mN. It can be seen that the fracture failure load of multi-layer coating is significantly higher than that of single-layer TiN coating; with the increase of the number of coating layers, the critical load psub>f increases. This is because the middle layer in the multilayer coating can prevent crack initiation and propagation (the ability of the middle layer to prevent crack initiation and propagation is related to its thickness and number of layers). According to a certain document, the fracture toughness Ksub>IC of the coating can be calculated by the following formula:
E and v are the elastic modulus and Poisson's ratio of the coating; 2pRC is the length of the crack in the coating; t is the coating thickness; U is the strain energy before and after the crack appears. The area on the ph curve reflects the elastoplastic deformation energy of the coating/matrix system. The strain energy U that is released when the first crack that is approximately circularly penetrating through the film is calculated from the product of the steps at the curve. Kazmanli et al. also described the relationship between steps and crack formation on the ph curve. From the formula (1), the fracture toughness of the four types of coatings was 1.51 MPa·m1â„2, 2.18 MPa·m1â„2, 3.4 MPa·m1â„2, and 3.9 MPa·m1â„2. It can be seen that as the number of coating layers increases, the fracture toughness value increases. However, the use of multi-layer coating increases the complexity and cost of the process, so the appropriate number of layers should be selected. For this reason we recommend TiN/Ti(C, N)/TiC/Ti(C, N)/TiC coatings. The ph curve describes the fracture failure of the coating; the p-h2 curve can be used to reflect the changes in the coating/substrate boundary before the failure of the friction-reducing wear-resistant coating, especially the interfacial changes between multilayer coatings. For single-phase materials, the plastic deformation component is hp and the elastic deformation component is he in the depth of press. Then, the total indentation depth h: f and y are parameters related to the geometry of the indenter; p is the load; HV is the hardness; E is the elastic modulus. Therefore, we can get p=Kh2, K is the Loubet elasto-plastic parameters. For a single body phase material, pâˆh2. When studying the coating/matrix system, it was found that the straight line from the origin to the inflection point on the typical p-h2 curve satisfies the pâˆh2 relationship, reflecting the elastic-plastic deformation of the coating. According to the analysis of Hertz contact theory, it was found that the maximum shear stress is still located in the pressed coating, and finally the matrix can yield, so the straight line segment reflects only the deformation of the coating. After crossing the inflection point, the high shear stress causes the substrate to yield, so that the coating is bent, the interface changes, part of the interface desorbs during the unloading process, and material accumulation occurs around the contact area under the effect of tensile stress until Cracks appear at the steps. Therefore, the load at the inflection point pi is used to represent the critical load of the coating layer. The p-h2 and ph curve completely reflect the entire process of coating interface change and fracture failure. The p-h2 curves for the four coatings, the dashed line is the line that meets pâˆh2, the solid line is the p-h2 curve during the indentation process, and the inflection point is at the separation point between the solid line and the dotted line. Any line segment from the origin to the inflection point reflects the deformation of the coating itself, where the load value at the inflection point is lower than the load value at the step. Through SFM observation, it can be found that cracks appear on the surface of the coating under the corresponding step load. From the indentation test data, it can be seen that the single-layer TiN coating undergoes an interface change at pi=3.13 mN, indicating that the monolayer coating has weaker interface bonding and the coating has poorer toughness. However, TiN/Ti(C, N)/TiC coatings exhibited interface changes at pi=7.5 mN. The straight line from the origin to the step (solid, dotted line), indicating that the two kinds of coatings at the end of the fracture failure occurred significant changes in the interface. Therefore, TiN/Ti(C, N)/TiC/Ti(C, N)/TiC and TiN/Ti(C, N)/TiC/Ti(C, N)/TiC/Ti(C, N)/TiC are more The layer coating has a higher interface strength and better toughness.
The surface of the wear-resistant brittle coating material breaks, peels, and breaks during the friction process. At this time, the wear resistance of the coating mainly depends on the material's resistance to brittle failure. Therefore, increasing the material's strength and fracture toughness can increase its wear resistance. Taking into account the material quality factors (here does not consider the friction zone temperature and chemical wear and other effects, if you need to be corrected when considering the temperature effect), the wear resistance of the coating material WR can be expressed as:
WR=KIC0.5E-0.8HV1.43 (4) Where: WR is wear resistance; KIC is fracture toughness (MPa·m1â„2); E is elastic modulus (GPa); HV is hardness (GPa). The following table shows the wear resistance of the four coatings calculated according to equation (4). It can be seen that TiN/Ti(C, N)/TiC/Ti(C, N)/TiC/Ti(C, N)/TiC coatings have the best wear resistance, and the results are comparable to those of cutting test results. . The cutting test results show that the TiN/Ti(C,N)/TiC/Ti(C,N)/TiC/Ti(C,N)/TiC coated tools have the longest service life among the four coatings investigated. Table 1 Mechanical properties and wear resistance of the coating
(mN) pf
(mN) KIC
(MPa·m1â„2) WR TiN 3.13 11.1 1.51 1.08 TiN/Ti(C,N)/TiC 7.50 16.4 2.18 1.42 TiN/Ti(C, N)/TiC/Ti(C, N)/TiC - 35.5 3.40 1.61 TiN/ Ti(C, N)/TiC/Ti(C, N)/TiC/Ti(C, N)/TiC - 56.3 3.90 1.84 3 Conclusion The formation of cracks in the coating is very similar to the step on the curve of load and indentation depth. Good correspondence. The mechanical properties of the coating material can be fully described by the flat force curve and the load and press-in depth curves of the load and the press-in depth. The step on the load and press-in depth curve can be used to describe the fracture failure of the coating, while the sinker segment on the square of the load and press-in depth can be used to describe the interface variation of the multilayer coating. The fracture failure and interface change of the coating can be described by the critical loads pf and pi, respectively. Multilayer coatings have high hardness, fracture toughness, and wear resistance. With the increase of the number of coating layers, the ultimate load pf and pi tend to increase. Among them, the mechanical properties and wear resistance of TiN/Ti(C, N)/TiC/Ti(C, N)/TiC/Ti(C, N)/TiC coatings are the best.
E and v are the elastic modulus and Poisson's ratio of the coating; 2pRC is the length of the crack in the coating; t is the coating thickness; U is the strain energy before and after the crack appears. The area on the ph curve reflects the elastoplastic deformation energy of the coating/matrix system. The strain energy U that is released when the first crack that is approximately circularly penetrating through the film is calculated from the product of the steps at the curve. Kazmanli et al. also described the relationship between steps and crack formation on the ph curve. From the formula (1), the fracture toughness of the four types of coatings was 1.51 MPa·m1â„2, 2.18 MPa·m1â„2, 3.4 MPa·m1â„2, and 3.9 MPa·m1â„2. It can be seen that as the number of coating layers increases, the fracture toughness value increases. However, the use of multi-layer coating increases the complexity and cost of the process, so the appropriate number of layers should be selected. For this reason we recommend TiN/Ti(C, N)/TiC/Ti(C, N)/TiC coatings. The ph curve describes the fracture failure of the coating; the p-h2 curve can be used to reflect the changes in the coating/substrate boundary before the failure of the friction-reducing wear-resistant coating, especially the interfacial changes between multilayer coatings. For single-phase materials, the plastic deformation component is hp and the elastic deformation component is he in the depth of press. Then, the total indentation depth h: f and y are parameters related to the geometry of the indenter; p is the load; HV is the hardness; E is the elastic modulus. Therefore, we can get p=Kh2, K is the Loubet elasto-plastic parameters. For a single body phase material, pâˆh2. When studying the coating/matrix system, it was found that the straight line from the origin to the inflection point on the typical p-h2 curve satisfies the pâˆh2 relationship, reflecting the elastic-plastic deformation of the coating. According to the analysis of Hertz contact theory, it was found that the maximum shear stress is still located in the pressed coating, and finally the matrix can yield, so the straight line segment reflects only the deformation of the coating. After crossing the inflection point, the high shear stress causes the substrate to yield, so that the coating is bent, the interface changes, part of the interface desorbs during the unloading process, and material accumulation occurs around the contact area under the effect of tensile stress until Cracks appear at the steps. Therefore, the load at the inflection point pi is used to represent the critical load of the coating layer. The p-h2 and ph curve completely reflect the entire process of coating interface change and fracture failure. The p-h2 curves for the four coatings, the dashed line is the line that meets pâˆh2, the solid line is the p-h2 curve during the indentation process, and the inflection point is at the separation point between the solid line and the dotted line. Any line segment from the origin to the inflection point reflects the deformation of the coating itself, where the load value at the inflection point is lower than the load value at the step. Through SFM observation, it can be found that cracks appear on the surface of the coating under the corresponding step load. From the indentation test data, it can be seen that the single-layer TiN coating undergoes an interface change at pi=3.13 mN, indicating that the monolayer coating has weaker interface bonding and the coating has poorer toughness. However, TiN/Ti(C, N)/TiC coatings exhibited interface changes at pi=7.5 mN. The straight line from the origin to the step (solid, dotted line), indicating that the two kinds of coatings at the end of the fracture failure occurred significant changes in the interface. Therefore, TiN/Ti(C, N)/TiC/Ti(C, N)/TiC and TiN/Ti(C, N)/TiC/Ti(C, N)/TiC/Ti(C, N)/TiC are more The layer coating has a higher interface strength and better toughness.
The surface of the wear-resistant brittle coating material breaks, peels, and breaks during the friction process. At this time, the wear resistance of the coating mainly depends on the material's resistance to brittle failure. Therefore, increasing the material's strength and fracture toughness can increase its wear resistance. Taking into account the material quality factors (here does not consider the friction zone temperature and chemical wear and other effects, if you need to be corrected when considering the temperature effect), the wear resistance of the coating material WR can be expressed as:
WR=KIC0.5E-0.8HV1.43 (4) Where: WR is wear resistance; KIC is fracture toughness (MPa·m1â„2); E is elastic modulus (GPa); HV is hardness (GPa). The following table shows the wear resistance of the four coatings calculated according to equation (4). It can be seen that TiN/Ti(C, N)/TiC/Ti(C, N)/TiC/Ti(C, N)/TiC coatings have the best wear resistance, and the results are comparable to those of cutting test results. . The cutting test results show that the TiN/Ti(C,N)/TiC/Ti(C,N)/TiC/Ti(C,N)/TiC coated tools have the longest service life among the four coatings investigated. Table 1 Mechanical properties and wear resistance of the coating
(mN) pf
(mN) KIC
(MPa·m1â„2) WR TiN 3.13 11.1 1.51 1.08 TiN/Ti(C,N)/TiC 7.50 16.4 2.18 1.42 TiN/Ti(C, N)/TiC/Ti(C, N)/TiC - 35.5 3.40 1.61 TiN/ Ti(C, N)/TiC/Ti(C, N)/TiC/Ti(C, N)/TiC - 56.3 3.90 1.84 3 Conclusion The formation of cracks in the coating is very similar to the step on the curve of load and indentation depth. Good correspondence. The mechanical properties of the coating material can be fully described by the flat force curve and the load and press-in depth curves of the load and the press-in depth. The step on the load and press-in depth curve can be used to describe the fracture failure of the coating, while the sinker segment on the square of the load and press-in depth can be used to describe the interface variation of the multilayer coating. The fracture failure and interface change of the coating can be described by the critical loads pf and pi, respectively. Multilayer coatings have high hardness, fracture toughness, and wear resistance. With the increase of the number of coating layers, the ultimate load pf and pi tend to increase. Among them, the mechanical properties and wear resistance of TiN/Ti(C, N)/TiC/Ti(C, N)/TiC/Ti(C, N)/TiC coatings are the best.
Roll Crusher Applications
Roll Crushers are simple in design and construction, long-lasting, economical, and versatile. Roll crushing surfaces operate at a fixed distance apart, as opposed to the continually changing distances in a jaw or Cone Crusher. Product size is much more consistent. Both oversized pieces and fined are minimized. Wet, sticky materials are more easily handled.
The rolls act as flywheels, contributing to smooth operation and efficient use of power. Roll crushers are low in profile and relatively easy to install. They can be fed with a minimum of headroom, or even choke fed. Adjustments are simple. Internal parts are readily accessible.
Typical feed materials for Roll Crushers include: bauxite, cement clinker, chalk, cinders, clay, coal, glass, gypsum, limestone, burnt lime, rock salt, sandstone, shale, sulfur ore, sea shells, and sewer sludge clinker. Single Roll Crushers, sometimes called lump breakers, can also be used for breaking frozen or agglomerated materials.
Roll Crusher
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