A poly crystalline diamond-cemented carbide monolithic helical cutter additive manufacturing process

Abstract

The present application relates to a kind of preparation methods of cutting tool, specifically to a kind of polycrystalline diamond-hard alloy integral spiral cutting tool additive manufacturing process.The present application is shaped by additive manufacturing respectively with grooved hard alloy substrate green body, matching groove type diamond PCD blade green body, after hard alloy substrate green body is debound presintering, with the debound diamond blade blank is combined after using interference fit way, high temperature and high pressure treatment is carried out, and spiral structure PCD cutting tool bit is obtained;The pressure of high temperature and high pressure treatment is 5~10GPa, and the temperature is 1400~1700 ℃.The present application not only avoids a series of problems such as thermal damage caused by bit welding, poor heat resistance, etc., but also obtains hard alloy-polycrystalline diamond composite with high interface bonding strength.The present application process is simple and controllable, and the performance of the obtained product is excellent, and it is easy to industrialize application.

Description

TECHNICAL FIELD

[0001] The present application relates to a tool manufacturing method, in particular to a kind of poly crystalline diamond (PCD)-cemented carbide integral spiral tool additive manufacturing process. BACKGROUND

[0002] As a kind of superhard material, poly crystalline diamond (PCD) has extremely high hardness and wear resistance, and the tool made of PCD and cemented carbide can significantly improve machining efficiency and quality in machining high-strength aluminum alloy, carbon fiber composite material and other difficult-to-cut materials, so it has wide application prospect in aerospace, automobile, die manufacturing and other high-end manufacturing fields.

[0003] Compared with flat edge structure tool, spiral structure PCD tool has the following outstanding advantages: Spiral edge participates in cutting longer and more stable, cutting force distribution is more uniform, impact load is lower, machining stability is higher, and cutting process window is wider; Chip removal efficiency is significantly improved compared with straight groove of flat edge structure tool, and the tool is more widely applicable; Cutting heat is more evenly dispersed, thermal damage failure is reduced, and tool life is improved; Spiral edge gradually participates in cutting, avoids instantaneous stress concentration of flat edge, and is more suitable for machining of hard and brittle materials and fiber composite materials and other difficult-to-machine materials.

[0004] Traditional PCD cutters are mainly prepared by welding and machining combination. For example, patent applications CN116117334A and CN113977641A disclose that a PCD large wafer prepared by high temperature and high pressure is cut according to a target cutter structure, and then welded with a cutter base with a reserved groove, and then the cutter shape and size precision requirements are realized through multiple machining processes such as turning, milling and grinding. Although the welding process can realize the combination of PCD and hard alloy, it has high requirements for the welding process, and needs to accurately control the welding temperature, time and other parameters. However, the commonly used high-frequency welding and laser welding are difficult to accurately control, which may cause problems such as loose welding and virtual welding. In addition, due to the high temperature in the welding process, the thermal stress at the connection may easily damage the cutter when it is subjected to a large cutting force or impact force, affecting the overall strength and reliability of the cutter and reducing its service life. Furthermore, due to the limitation of the original length-diameter ratio of the PCD blade and the limitation of the machining process by the cutter and the grinding tool, it is difficult to prepare complex shape integral spiral cutters such as large angle and multi-rotation. Since the current PCD cutters are mainly prepared by cutting and welding large-diameter thin polycrystalline diamond composite sheets, and then machining to achieve the target cutter structure and size precision, the obtained PCD cutters are planar edge structure, which is difficult to realize the welding and machining of spiral structure cutters. Moreover, the existing PCD cutters prepared by welding polycrystalline diamond composite sheets have a work layer close to the welding surface, and the cutting heat and cutting force generated during the cutting process significantly affect the bonding strength of the welding surface, resulting in reduced machining precision or premature failure of the PCD cutter.

[0005] In recent years, there have been some reports on integral PCD cutters. For example, patent CN118357467A uses a pressing process to form a spiral structure diamond layer on the surface of a hard alloy rod, and then burns the diamond and hard alloy into one body under high temperature and high pressure process conditions, which can realize the preparation of large-angle PCD spiral cutter head. However, since the HTHP process needs to place the hard alloy base and diamond powder combination in a metal cup made of molybdenum, zirconium or niobium under high temperature and high pressure, the powder pressing process is difficult to operate and has low efficiency, and the machining and positioning of the hard alloy cutter head with spiral grooves are difficult. SUMMARY

[0006] Since the current PCD cutters are mainly prepared by cutting and welding thin PCD large wafers (<1mm) with hard alloy, the actual PCD life is difficult to reach its intrinsic material performance due to the limitation of solder strength and welding temperature. Due to the limitation of PCD flat sheet structure, it is difficult to meet the preparation of large-angle, multi-rotation and other structure PCD cutters under complex working conditions. Therefore, the present application provides a high-efficiency and simple PCD cutter preparation method with high design freedom for the first time.

[0007] The application discloses a kind of poly crystalline diamond-cemented carbide integral spiral cutter additive manufacturing processes, by additive manufacturing respectively forming grooved cemented carbide matrix green body, matching groove diamond (PCD) blade green body, after cemented carbide matrix green body is defatted presintering, after defatting with the diamond blade blank of presintering, it is combined after high temperature and high pressure treatment using interference fit, obtain spiral structure PCD cutter bit;The pressure of high temperature and high pressure treatment is 5~10GPa, preferably 6~8GPa, temperature is 1400~1700 DEG C, preferably 1450~1550 DEG C.

[0008] In the application, the reason why the cemented carbide matrix green body is defatted presintered and then combined with the diamond blade blank after defatting by interference fit is that the shrinkage rates of the cemented carbide green body and the diamond green body are different, which can easily cause the deformation and collapse of the combined structure. In the technical exploration, it is found that if the temperature of the cemented carbide matrix green body is too high and the time of the defatting presintering is too long, the matrix sintering densification will occur, the migration of Co in the matrix to the diamond blade will be enhanced, the performance of the blade will be reduced, the interface bonding between the matrix and the diamond blade in the densification process will be poor, and the machining amount will be increased due to the large size shrinkage difference in the high temperature and high pressure process. If the diamond green body is also presintered after defatting, the designed structure will be easily deviated and the performance of the finished product will be reduced. Based on the above exploration, the scheme of the application is optimized.

[0009] In the application, the PCD blade green body can be prepared by the powder filling method or additive manufacturing processes such as PEP, FDM, FFF, SLA, BJP and SLS. In the small-angle spiral structure cutter, the powder filling method can be used for filling, but in the large-angle spiral structure, it is difficult to achieve dense filling, which leads to a large PCD removal amount after HTHP, a low PCD retention amount and high machining cost.

[0010] The grooved cemented carbide matrix green body can be prepared by machining grooving or additive manufacturing processes such as laser, PEP, FDM, FFF, SLA, BJP and SLS. The surface of the machined groove is smooth, the bonding area between the PCD blade and the groove is reduced, the interface bonding strength is reduced, and the cutting stability is reduced.

[0011] In actual application, the cutter head obtained by the above scheme is further installed with a tool shank, ground for outer circle, arranged with a chip removal groove and machined for a blade edge to obtain a target structure PCD cutter. High-strength interface bonding between the PCD blade and the cemented carbide matrix and high retention amount of the PCD blade are achieved to meet the preparation requirements of special structure PCD cutters under complex working conditions.

[0012] As an optimization, the application discloses a kind of poly crystalline diamond-cemented carbide integral spiral cutter additive manufacturing processes, and the specific technical scheme is as follows:

[0013] (1) Diamond feedstock preparation: with organic polymer material, binder, diamond powder as raw material, through mixing, crushing, screening to get diamond feedstock; wherein, the mass ratio of diamond and binder is 90-99:1-10, preferably 93-97:3-7; the powder loading of diamond+binder is 45-60vol.%, preferably 50-55vol.%; the binder is at least one of Co, Ni, Co-Ni, Co-Ni-Fe, Mo, Al-Si, preferably Co; the particle size of diamond is less than or equal to 35μm, which can be a single particle size. Particle size grading can also be used, but the main particle size is preferably 1-20μm.

[0014] The organic polymer material includes filler, skeleton, plasticizer, surfactant, and the mass ratio is 55-75:25-40:2-5:3-5 respectively; the filler includes one or more of polyformaldehyde (POM), polyethylene glycol (PEG), solid paraffin (PW), liquid paraffin (LPW), microcrystalline wax (MW), preferably PW and MW mixed in a mass ratio of 40-50:15-20; the skeleton includes one or more of high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), ethylene-vinyl acetate copolymer (EVA), polylactic acid (PLA), preferably HDPE and EVA mixed in a mass ratio of 20-25:10-15; the plasticizer is selected from at least one of dioctyl phthalate (DOP), dibutyl phthalate (DBP), trimethylphenyl phosphate (TCP), tributyl citrate (TBC), preferably DOP; the surfactant is selected from at least one of stearic acid (SA) and oleic acid (OA), preferably SA.

[0015] (2) Cemented carbide feedstock preparation: with organic polymer material and cemented carbide powder as raw material, through mixing, crushing, screening to get cemented carbide feedstock; wherein, the powder loading of cemented carbide powder is 50-70vol.%, preferably 60-65vol.%; the Co content of cemented carbide powder is 5-16wt.%, preferably 8-10wt; the WC grain size range is less than or equal to 10μm, preferably 0.2-3μm. 0.5-3wt.% of W powder is mixed in the cemented carbide powder to make the matrix after sintering show a carbon-poor structure to avoid the influence of residual carbon that may exist in the heat defatting; at the same time, the slight carbon-poor structure is conducive to inhibiting the abnormal WC grain growth at the interface between the cemented carbide matrix and PCD, and slowing down the stress concentration at the interface.

[0016] The organic polymer material includes a filler, a skeleton, a plasticizer, and a surfactant, and the mass ratio is 45-80:20-45:2-5:1-5; the filler includes one or more of polyoxymethylene (POM), polyethylene glycol (PEG), solid paraffin (PW), liquid paraffin (LPW), and microcrystalline wax (MW), and preferably, the PW and the MW are mixed at a mass ratio of 40-50:10-40; the skeleton includes one or more of high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), and ethylene-vinyl acetate copolymer (EVA), and preferably, the HDPE and the EVA are mixed at a mass ratio of 10-30:10-30; the plasticizer is at least one selected from dioctyl phthalate (DOP), dibutyl phthalate (DBP), and tricresyl phosphate (TCP), and preferably, the DOP; and the surfactant is at least one selected from stearic acid (SA) and oleic acid (OA), and preferably, the SA.

[0017] (3) Green body additive manufacturing: the target three-dimensional structure of the hard alloy substrate and the PCD blade are converted into a multi-layer two-dimensional structure graph recognizable by the printing equipment through slicing software, and the printing parameters are set; the diamond feedstock and the hard alloy feedstock prepared in steps (1) and (2) are printed according to the set parameters to obtain a hard alloy substrate (corresponding to the tool bit substrate) and a diamond (corresponding to the PCD blade) of the target three-dimensional structure.

[0018] Based on the preferred diamond feedstock and hard alloy feedstock formula in steps (1) and (2), the printing parameters of the diamond green body are preferably: layer thickness 0.05-0.15 mm, nozzle size (i.e., line width) 0.2-0.4 mm, printing temperature 120-140℃, platform temperature 50-70℃, and printing speed 10-25 mm / s; and the printing parameters of the hard alloy green body are preferably: layer thickness 0.1-0.25 mm, nozzle size 0.2-0.8 mm, printing temperature 120-150℃, platform temperature 50-90℃, and printing speed 20-50 mm / s. Smaller layer thickness, line width, and printing speed can achieve higher precision of the green body printing, but the printing efficiency will be reduced, and the printing parameters can be further optimized according to the model size. In addition, considering the orientation of the 3D printing process, the model is printed along the model helical groove axis to ensure the precision of the formed structure. For the diamond blade with a large helix angle, a support model can be constructed to ensure the forming precision, and the support structure can be removed before being combined with the hard alloy substrate.

[0019] (4) Solvent degreasing: respectively, the hard alloy, diamond printing green body is placed in the degreasing solvent for degreasing treatment to remove paraffin, DOP, SA and other low molecular weight organic polymers, to obtain the degreasing brown blank. The degreasing solvent can be n-heptane, kerosene and the like. The solvent degreasing process is 30-60℃, and the degreasing time is 12-36h.

[0020] (5) Hard alloy pre-sintering: the vacuum degreasing-sintering integrated furnace is used for heat degreasing and sintering of the hard alloy. The heat degreasing stage is from room temperature to 600-650 ℃, the heating rate is 0.5-2 ℃ / min, and the time is 90-180 min to remove the organic polymer skeleton; the pre-sintering temperature is 900-1300℃, preferably 1000-1100℃, the heating rate is 3-8 ℃ / min, and the time is 60-120 min; so that the hard alloy blank has certain strength and density.

[0021] (6) Diamond and hard alloy assembly: the diamond degreasing blank and the hard alloy pre-sintering blank are assembled with interference, and then placed in a molybdenum / zirconium / niobium metal cup for high temperature and high pressure, and the diamond layer is subjected to heat degreasing and raw material purification treatment. The heat degreasing process is from room temperature to 600-650 ℃, and the heating rate is 0.5-2 ℃ / min to remove the organic polymer skeleton; the raw material purification process is 900-1000℃ vacuum heat treatment for 1-2h, and the heating rate is 2-5 ℃ / min to remove the impurities on the surface of the diamond.

[0022] (7) High temperature and high pressure sintering: the diamond-hard alloy combined structure in the metal cup in step (6) is assembled with salt tube, graphite tube and talc tube from inside to outside layer by layer gap, to obtain a synthesis block for high temperature and high pressure, and then placed in a hexahedral press for high temperature and high pressure synthesis, to obtain a spiral structure PCD cutter bit. The synthesis process is pressure: 5.5-7.5GPa, preferably 7-7.5GPa, temperature: 1400-1700℃, preferably 1450-1550℃.

[0023] As preferred, in the raw material diamond used, the mass ratio of diamond with particle size A: diamond with particle size B = 60~80:40~20, further preferably 70~80:30~20; the value of A is 8~20 microns, and the value of B is less than or equal to 3 microns, preferably 0.5-2 microns.

[0024] In step (1), the diamond feedstock is prepared by mixing, compounding, crushing and screening with organic polymer material, binder and diamond powder, and the 8-20 mesh feedstock is preferably used for printing.

[0025] In step (2), the cemented carbide feedstock is prepared: using organic polymer and cemented carbide powder as raw materials, the cemented carbide feedstock is prepared by mixing, compounding, crushing and screening, and the feedstock with a particle size of 8-20 is preferably used for printing.

[0026] In steps (5) and (6) of the application, the diamond green body is assembled with the cemented carbide pre-sintered body after debinding, because the diamond content in the diamond feedstock powder is more than 90%, and it is difficult to form strength through pre-sintering; and the diamond printed green body is combined with the cemented carbide printed green body for debinding and pre-sintering, because the pre-sintering shrinkage rates of the cemented carbide green body and the diamond green body are different, which easily leads to the collapse of the diamond blade structure due to the lack of strength.

[0027] The purpose of the heat debinding purification and high-temperature vacuum purification treatment in the application is to remove the residual polymer skeleton in the diamond blade after solvent debinding, the surface residual impurities in the diamond powder preparation process, and to change the surface state of the diamond powder, improve the surface atom activity and diffusion capacity of the powder in the high-temperature high-pressure reaction process, and accelerate the formation of the diamond skeleton. If the purification temperature is too high and the time is too long, it will lead to graphitization of the diamond, which will damage its quality and performance. If no purification treatment is performed or the purification is not complete, the residual organic matter or impurities will affect the formation of the polycrystalline diamond skeleton in the high-temperature high-pressure process, reduce the quality and yield of PCD, and affect the service life of the tool and the machining quality and other series of problems.

[0028] In the application, the high-temperature high-pressure sintering can be: the diamond-cemented carbide combined structure in step (6) is assembled in a metal cup, and the salt tube, graphite tube and pyrophyllite tube are assembled from the inside to the outside layer by layer, to obtain a synthesis block for high-temperature high-pressure, and then the synthesis block is placed in a hexahedral press for high-temperature high-pressure synthesis, to obtain a spiral structure PCD tool bit.

[0029] The additive manufacturing process of the polycrystalline diamond-cemented carbide integral spiral tool of the application obtains the spiral structure PCD tool bit through steps (1)-(7), and then connects the tool handle to obtain the tool finished product after subsequent processing. The specific scheme is: after high-temperature high-pressure, the spiral structure PCD tool bit is obtained, the metal cup is removed after outer circle and end face grinding, and then the PCD tool blank is obtained by welding the tool handle; then the excess cemented carbide matrix is removed by diamond grinding wheel and electrolytic grinding wheel, and the PCD tool chip groove is processed; then the PCD edge is processed by wire cutting or laser processing, to obtain the PCD tool with high dimensional accuracy and surface finish. Of course, after obtaining the spiral structure PCD tool bit, other processing methods are also suitable for the application.

[0030] The application adopts additive manufacturing to prepare a polycrystalline diamond-cemented carbide integral spiral structure cutter, since a welding process is not introduced, the prepared cutter can maintain the intrinsic material performance of PCD, and the cutter life is greatly improved; the PCD cutting edge is an integral spiral structure, and has better machining performance. In the application, the high powder loading of the diamond feed, and the diamond debinding blank still has certain strength and plasticity, so that the sintering shrinkage of the diamond layer in the HTHP process is greatly reduced under the premise of ensuring high filling density of the PCD cutting edge. The layered printing lines of the cemented carbide substrate increase the interface contact area of the cemented carbide substrate and the diamond debinding blank; the incomplete densification of the cemented carbide pre-sintered body and the diamond debinding blank is sintered and densified in the high temperature and high pressure process, which is beneficial to improving the interface bonding strength of the two. In addition, since the PCD cutting edge part is assembled according to the required structure design, the actual PCD cutting edge machining amount is greatly reduced.

[0031] Principle and advantage

[0032] The application adopts the process route that the cemented carbide substrate and the diamond cutting edge are printed separately and then combined at high temperature and high pressure; the application not only avoids a series of problems such as thermal damage and poor heat resistance caused by tool head welding, but also obtains a cemented carbide-polycrystalline diamond composite with high interface bonding strength.

[0033] The application adopts additive manufacturing with appropriate parameters to prepare the cemented carbide substrate, which not only improves the design freedom of the spiral structure cutter, but also improves the contact area of the substrate and the PCD cutting edge due to the characteristic layered structure of additive manufacturing, and is beneficial to improving the interface bonding strength of the two.

[0034] The application adopts the debinding blank with high diamond content to fill the cemented carbide alloy substrate, since the debinding blank contains a mixed polymer containing a skeleton and a small amount of a filler, a plasticizer and a surfactant, and has certain strength and plasticity, the PCD layer can be uniformly and densely filled in any structure cutter without printing a PCD cutting edge with high size structure precision.

[0035] In the application, the cemented carbide substrate and the PCD cutting edge are integrally formed and sintered, the cutting edge structure positioning is more accurate, and the PCD machining amount of the difficult-to-machine part is reduced, so that the cost is reduced and the efficiency is improved.

[0036] In the forming stage of the application, the equipment and process of each step are general in the traditional preparation process, and the applicability is wide and the upgrading cost is low. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 It is a principle diagram of the additive manufacturing integral PCD spiral cutter of the application;

[0038] Figure 2 It is an interface feature diagram of the PCD cutting edge and the cemented carbide;

[0039] Figure 3 This is a picture of the PCD tool head after it has been connected to the tool holder.

[0040] Figure 4 The image shows a real product of a spiral cutting tool, consisting of three smaller images: (a), (b), and (c). Image (a) is a top view of a cutting tool with a spiral angle of 5° in both directions; image (b) is a front view of a cutting tool with a spiral angle of 5° in both directions; and image (c) is a front view of a cutting tool with a single spiral propeller angle of 30°. Detailed Implementation

[0041] Example 1:

[0042] like Figure 1 As shown, the additively manufactured integral helical PCD tool consists of two parts: a cemented carbide matrix with helical grooves and a PCD cutting edge filled with helical grooves. The cemented carbide used has a composition of 10 wt.% Co, 1 wt.% W, and 89 wt.% WC, with the WC grain size being 1.6 μm; the PCD cutting edge powder composition is 75 wt.% 10 μm diamond, 20% 1 μm diamond, and 5 wt% 1-2 μm Co. Its fabrication process is as follows:

[0043] (1) The above diamond powder and Co powder are mixed to obtain diamond mixed powder; according to the mass ratio, PW:MW:EO:EVA:HDPE:DOP:SA=45:10:5:16:17:5:2, organic polymer is weighed; according to the volume ratio, organic polymer:diamond mixed powder=45:55, raw materials are prepared (corresponding to a powder loading of 55 vol.%). PW, MW, EO, EVA, HDPE, and DOP are added to the internal mixer in order of melting point and heated and mixed evenly. SA is added simultaneously with the powder in 3 batches. During the process, the temperature is lowered to allow the powder and organic polymer to be fully sheared and kneaded to ensure uniform mixing. Then, the cooled internally mixed material is crushed and sieved to obtain the target feed particles. The mixing temperature is 150℃, the cooling temperature-time is 125℃-30min, the total mixing time is 2h, and the feed sieve particle size is 8-20 mesh.

[0044] (2) The WC powder, W powder and Co powder are mixed to obtain cemented carbide mixed powder; the organic polymer is weighed according to the mass ratio of PW:MW:EO:EVA:HDPE:DOP:SA=45:10:5:16:17:5:2; the raw materials are prepared according to the volume ratio of organic polymer: cemented carbide mixed powder=40:60 (corresponding to the powder loading amount of 60 vol.%). The PW, MW, EO, EVA, HDPE and DOP are sequentially added into the internal mixer according to the melting point from high to low, and are uniformly heated and mixed, the SA is synchronously added in three times, and the powder is sheared and kneaded with the organic polymer during the temperature reduction to ensure uniform mixing, then the cooled internal mixing material is crushed and sieved to obtain the target feed granules. The internal mixing temperature is 145℃, the temperature reduction temperature and time are 125℃-30min, the total internal mixing time is 2h, and the feed sieving particle size is 8-20 meshes.

[0045] (3) The spiral structure cemented carbide substrate and the corresponding PCD blade model are introduced into the corresponding slicing software of the printer, and the printing parameters are set and the G code recognizable by the printer is output. The printing parameters of the cemented carbide substrate are set as follows: layer thickness 0.2mm, nozzle size 0.8mm, printing temperature 135℃, platform temperature 85℃, printing speed 40mm / s; the printing parameters of the PCD blade are set as follows: layer thickness 0.1mm, nozzle size 0.3mm, printing temperature 125℃, platform temperature 50℃, printing speed 15mm / s. The prepared diamond feed and cemented carbide feed are respectively placed in the feeding bin of the extrusion type 3D printer, and printing is carried out according to the preset parameters to obtain the cemented carbide and diamond printed blanks.

[0046] (4) The cemented carbide and diamond printed blanks are respectively placed in n-heptane for solvent removal treatment to obtain the corresponding solvent removal brown blanks. The solvent removal process is 50℃ for 14h.

[0047] (5) The cemented carbide solvent removal brown blank is placed in a vacuum debinding-sintering integrated furnace for thermal debinding and pre-sintering. The thermal debinding process is 2℃ / min to 400℃ for 1h, and then 1℃ / min to 600℃ for 1h; the pre-sintering process is 5℃ / min to 1000℃ for 1h.

[0048] (6) The diamond solvent removal brown blank and the cemented carbide pre-sintered blank are interference assembled, and are placed in a niobium cup matched with the size of the high-temperature and high-pressure synthesized block for thermal debinding and raw material purification treatment of the diamond layer. The thermal debinding process is 2℃ / min to 400℃ for 1h, and then 1℃ / min to 600℃ for 1h; the raw material purification process is 5℃ / min to 900℃ for 1h.

[0049] (7) The diamond-cemented carbide combination structure placed in the metal cup in step (6) is assembled into a high-temperature and high-pressure synthesis block in sequence with a salt tube, a carbon tube, a talc, a conductive sheet, and a graphite sheet to perform high-temperature and high-pressure sintering to obtain a spiral structure PCD cutter bit. The high-temperature and high-pressure synthesis process is 7 GPa-1500°C, and the holding time is 10 min.

[0050] (8) The spiral structure PCD cutter bit obtained in step (7) is combined and welded with a shank after the metal cup is removed by external circle and end face grinding to obtain a PCD cutter blank; then the PCD cutter chip flutes are processed by removing the excess cemented carbide matrix through a diamond grinding wheel and an electrolytic grinding wheel; and then the PCD cutting edges are processed by wire cutting or laser processing to obtain a PCD cutter with high dimensional precision and surface finish.

[0051] The prepared printing blank has a dense microstructure and high dimensional precision, and the solvent debinding has no bubbling and cracking defects. Compared with the model, the dimensional deviation of the cemented carbide matrix printing blank is less than 3%, and the pre-sintering density is 75%; and the dimensional deviation of the PCD cutting edge is less than 10%. After high-temperature and high-pressure synthesis, the radial shrinkage of the spiral structure PCD cutter matrix is 6.8%, the axial shrinkage is 5.6%, the radial shrinkage of the PCD cutting edge is 9.8%, and the axial shrinkage is 8.6%. The cemented carbide matrix and the PCD cutting edge are combined tightly, and there is an embedded area of interdiffusion and migration of diamond and cemented carbide components. For machining of 7075 series aviation aluminum alloy material, the machining parameters are set as follows: rotational speed 3800 r / min, feed rate 0.105 mm / z, cutting amount 1 mm, and cutting depth 0.5 mm. The service life of the prepared PCD cutter is 3517 m, which is 2.27 times that of the welded PCD cutter (1547 m).

[0052] Example 2:

[0053] The other conditions are the same as those in Example 1, except that the particle size of the diamond in the raw materials used is changed to only 95% 10 μm diamond, and the other raw materials and treatment methods remain unchanged.

[0054] The prepared printing blank can achieve similar dimensional precision. However, after high-temperature and high-pressure synthesis, the radial shrinkage of the PCD cutting edge increases to 11.2%, and the axial shrinkage increases to 9.9%. The cemented carbide matrix and the PCD cutting edge are combined tightly. Under the same test conditions as in Example 1, the service life of the prepared PCD cutter is 2977 m. However, due to the increased dimensional shrinkage of the PCD cutting edge, the difference in shrinkage rate between the cemented carbide and the PCD cutting edge increases. In order to obtain a spiral PCD cutter bit that can be welded with a shank, the machining amount of the external circle and end face of the cutter bit blank after synthesis increases, and the cost and cycle time increase.

[0055] Example 3: Other conditions are consistent with Example 1, except that the pre-sintering temperature of cemented carbide in Example 1 is adjusted to 1300℃, and the raw materials and other processing methods remain consistent with Example 1.

[0056] The prepared printing blank can achieve similar dimensional accuracy. However, the pre-sintering density of cemented carbide is increased to 89%, and after high-temperature and high-pressure synthesis, the radial shrinkage of the alloy matrix is reduced to 4.4%, and the axial shrinkage is reduced to 3.8%. Similarly, the gap between the PCD blade and the shrinkage of cemented carbide is increased, and the machining amount of the outer circle and end face of the blank after synthesis is increased, and the cost and cycle are increased. Under the same test conditions as Example 1, the service life of the prepared PCD cutter can reach 3254m.

[0057] Example 4

[0058] Other conditions are consistent with Example 1, except that the pre-sintering temperature in step (5) is 900℃.

[0059] The pre-sintering density of cemented carbide is increased to 68%, and after high-temperature and high-pressure synthesis, the radial shrinkage of the alloy matrix is increased to 8.8%, and the axial shrinkage is increased to 7.9%. The density of the alloy matrix is too low, and the deformation is large during the high-temperature and high-pressure process, and the time spent in the densification stage is longer. Under the same conditions, the time for forming the diamond skeleton and tightly combining with the matrix is shortened. Under the same test conditions as Example 1, the service life of the prepared PCD cutter is reduced to 3382m.

[0060] Example 5

[0061] Other conditions are consistent with Example 1, except that the proportion of organic macromolecular formula in step (2) is adjusted to PW:MW:EO:EVA:HDPE:DOP:SA=50:15:5:12:13:3:2. The filler is increased, and the flowability of the mixed macromolecule is increased. Under the premise of ensuring uniformity of the feed, more powder can be accommodated, and organic macromolecule:cemented carbide mixed powder=36:64 (corresponding to a powder loading of 64vol.%). The mixing temperature is reduced to 140℃. The printing temperature in step (3) is reduced to 130℃, and the platform temperature is reduced to 80℃.

[0062] The prepared printing blank can achieve similar dimensional accuracy. Due to the increase in powder loading, the pre-sintering density at 1000℃ is increased to 78%. Under the same test conditions as Example 1, the service life of the prepared PCD cutter can reach 3489m.

[0063] Example 6

[0064] Other conditions and embodiment 1 are consistent, except that the organic macromolecular formula ratio of step (1) is adjusted to PW:MW:EO:EVA:HDPE:DOP:SA=40:10:5:20:17:5:3. The filler in the organic macromolecular formula is reduced, the skeleton content is increased, and under the premise of ensuring the uniformity of the feed, the powder loading is reduced to 50vol.%. The temperature of the internal mixer is increased to 160℃. The printing temperature in step (3) is increased to 130℃, and the platform temperature is increased to 70℃.

[0065] The prepared printing blank can achieve similar dimensional accuracy. Due to the reduced loading of the diamond blade green powder, the filling density of the diamond mixed powder after thermal debinding decreases, the dimensional shrinkage rate of the diamond blade and the cemented carbide matrix increases after high temperature and high pressure, and the processing cost and cycle increase. Under the same test conditions as embodiment 1, the service life of the prepared PCD cutter can reach 3402m.

[0066] Embodiment 7: The cemented carbide formula in the raw materials used is adjusted to 10wt.%Co, 90wt.%WC, and other raw materials and processing methods remain unchanged. By using the same process and processing steps as embodiment 1, a whole PCD spiral milling cutter can be prepared.

[0067] But graphite phase is found in the pre-sintered cemented carbide matrix. After high temperature and high pressure synthesis, the graphite phase is converted into fine microcracks. The cemented carbide matrix and the PCD blade are still tightly combined, but there are many 3-7μm abnormally grown WC grains at the interface. Under the same test conditions as embodiment 1, the service life of the prepared PCD cutter can reach 3233m. Since the working layer of the PCD cutter is mainly the PCD blade, the adjustment of the alloy formula has little effect on the service life of the PCD cutter. However, the increase of microcracks in the alloy increases the risk of alloy fracture during high temperature and high pressure synthesis, and the yield of high temperature and high pressure synthesis decreases significantly. Among the actual 10 high-temperature and high-pressure synthesized cutter heads, only two are intact.

[0068] Comparative example 1: The alloy pre-sintering is adjusted to 1400-1450℃ densification sintering, and other raw materials and processing methods remain unchanged. The same process and processing steps as embodiment 1 are used.

[0069] In the obtained product, the interface between the cemented carbide matrix and the PCD blade has a 10-20μm interface Co-rich zone similar to PDC, but there is no obvious grain diffusion and migration phenomenon. And because the cemented carbide is a dense body, the tendency of Co diffusion and migration from the matrix to the PCD blade increases under high temperature and high pressure conditions, and the Co content of the PCD blade increases. Under the same conditions, the service life of the prepared PCD cutter is reduced to 2599m. In addition, since the cemented carbide hardly shrinks, the dimensional shrinkage difference between the PCD and the alloy increases significantly, the processing amount increases significantly, and the processing cost and cycle increase significantly.

[0070] Comparative Example 2: The cemented carbide formulation was adjusted to 5wt.% W, 10wt.% Co, 85wt.% WC in the raw materials used, and the other raw materials and processing methods remained unchanged. The same process and processing steps as in Example 1 were used. Due to the high W content, a eta phase carbon-poor organization was formed inside the cemented carbide, increasing the brittleness of the alloy, leading to the alloy breaking easily during the cold pressing stage of the high temperature and high pressure process, and the complete monolithic PCD spiral cutter could not be prepared.

[0071] Comparative Example 3: The other conditions were the same as in Example 1, except that the main particle size of the diamond was adjusted to 95% 40pm diamond in the raw materials used, and the other conditions were the same as in Example 1. Due to the increase in the main particle size, it was not possible to achieve the 0.1mm layer thickness and 0.3mm trace width in Example 1. The PCD blade printing parameters were adjusted to a layer thickness of 0.2mm and a trace width of 0.6mm. The X / Y / Z size deviation of the PCD blade printing blank was >20%, the structural precision was reduced, the size matching of the PCD blade debinding blank and the cemented carbide pre-sintered blank was reduced, it was difficult to form a tight bond, and local material shortages were prone to occur, resulting in incomplete PCD blade after high temperature and high pressure synthesis.

[0072] Comparative Example 4: The other conditions were the same as in Example 1, except that the diamond feed powder loading in Example 1 was adjusted to 65%, and the powder raw materials and other conditions remained unchanged. The prepared feed was viscous, had poor flowability, and had poor mixing uniformity, with local powder agglomeration defects. Adjusting the printing temperature, layer thickness, nozzle size, platform temperature, etc. could not achieve smooth extrusion of the feed. High printing temperature would cause unstable outflow of the nozzle during the printing process, and low printing temperature would not allow extrusion. Increasing the nozzle size could achieve printing, but could not change the defects of uneven feed, and would further reduce the printing precision.

[0073] Comparative Example 5: The other conditions were the same as in Example 1, except that the skeleton content of the organic polymer in the feed was increased in Example 1, and the polymer ratio was adjusted to PW:MW:EO:EVA:HDPE:DOP:SA=23:5:5:30:30:5:2. The other raw materials and processing methods remained unchanged. The viscosity of the feed increased, the flowability decreased, and the mixing uniformity was poor. Similarly, it was not possible to achieve smooth extrusion of the feed by adjusting the printing temperature, layer thickness, nozzle size, platform temperature, etc.

[0074] Comparative Example 6: Other conditions are consistent with Example 1, except that the solvent debinding process is adjusted to 70°C, and other raw materials and processing are consistent with Example 1. Increasing the temperature, the solvent debinding time can be shortened to 6-8h, but the solvent debinding speed is too fast, which will lead to the generation of bubbles in the green body and even delamination defects. Taking the cemented carbide substrate as an example, the bubbling and delamination defects in the pre-sintering process cannot be eliminated, and the fracture occurs in the high temperature and high pressure synthesis process. The volume of the PCD blade is small, and due to the support of the cemented carbide substrate, the bubbling and delamination defects of the debinding green body will not cause fracture defects, but will cause local composition unevenness and increase the shrinkage.

[0075] Comparative Example 7: Other conditions are consistent with Example 1, except that the heating rate of the cemented carbide substrate is adjusted to 5°C / min in the thermal debinding process, and other raw materials and processing are consistent with Example 1. There are local undecomposed polymers in the cemented carbide, which are carbonized at high temperature and remain in the alloy, forming local defects. After high temperature and high pressure synthesis, the alloy is fractured, and a complete PCD spiral cutter bit cannot be prepared.

Claims

1. A process for additive manufacturing of a polycrystalline diamond-cemented carbide solid helical cutter, characterized by: The hard alloy substrate green body with a groove type and the diamond PCD blade green body with a matching groove type are respectively formed by additive manufacturing, the hard alloy substrate green body is debound and pre-sintered, then the debound diamond blade green body is combined with the hard alloy substrate green body in an interference fit mode, and high-temperature and high-pressure treatment is performed, so that a spiral structure PCD cutter head is obtained; the pressure of the high-temperature and high-pressure treatment is 5-10 GPa, and the temperature is 1400-1700 ℃; Specifically comprising the following steps: (1) Diamond feedstock preparation: taking organic polymer material, binder, and diamond micro powder as raw materials, diamond feedstock is prepared by mixing and densifying, crushing, and sieving; wherein the mass ratio of diamond to binder is 90-99:1-10; the powder loading amount of diamond+binder is 45-60 vol.%; the binder is at least one of Co, Ni, Co-Ni, Co-Ni-Fe, Mo, and Al-Si; the particle size of diamond is less than or equal to 35 μm; The organic polymer material includes a filler, a skeleton, a plasticizer, and a surfactant, and the mass ratio is 55-75:25-40:2-5:3-5; (2) Hard alloy feedstock preparation: taking organic polymer material and hard alloy powder as raw materials, hard alloy feedstock is prepared by mixing and densifying, crushing, and sieving; wherein the powder loading amount of hard alloy powder is 50-70 vol.%; the Co content of hard alloy powder is 5-16 wt.%; the WC grain size range is less than or equal to 10 μm; The organic polymer material includes a filler, a skeleton, a plasticizer, and a surfactant, and the mass ratio is 45-80:20-45:2-5:1-5; The filler used for preparing the diamond feedstock and the hard alloy feedstock includes one or more of polyformaldehyde, polyethylene glycol, solid paraffin, liquid paraffin, and microcrystalline wax; the skeleton includes one or more of high-density polyethylene, low-density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, and polylactic acid; the plasticizer is at least one selected from dioctyl phthalate, dibutyl phthalate, trimethylphenyl phosphate, and tributyl citrate; and the surfactant is at least one selected from stearic acid and oleic acid; (3) Green body additive manufacturing: the target three-dimensional structure hard alloy substrate and PCD blade are converted into a multi-layer two-dimensional structure graph recognizable by a printing device through slicing software; and printing parameters are set; the diamond feedstock and the hard alloy feedstock prepared in steps (1) and (2) are printed according to the set parameters, so that the target three-dimensional structure hard alloy substrate green body and the corresponding PCD blade diamond printing green body are obtained. Based on the diamond feeding, hard alloy feeding formula of step (1), (2), the diamond green body printing parameter selection is: layer thickness 0.05-0.15mm, nozzle size 0.2-0.4mm, printing temperature 120-140℃, platform temperature 50-70℃, printing speed 10-25mm / s; the hard alloy green body printing parameter selection is: layer thickness 0.1-0.25mm, nozzle size 0.2-0.8mm, printing temperature 120-150℃, platform temperature 50-90℃, printing speed 20-50mm / s; (4) solvent debinding: respectively, the hard alloy, diamond printing green body is put into the debinding solvent for debinding, and the debinding brown body is obtained; the solvent debinding process is 30-60℃, and the debinding time is 12-36h; (5) hard alloy presintering: the vacuum debinding-sintering integrated furnace is used for heat debinding and sintering of the hard alloy; wherein the heat debinding stage is room temperature to 600-650℃, the heating rate is 0.5-2℃ / min, and the time is 90-180min, to remove the organic polymer skeleton; the presintering temperature is 900-1300℃, the heating rate is 3-8℃ / min, and the time is 60-120min; (6) diamond and hard alloy assembly: the diamond debinding body and the hard alloy presintering body are assembled with interference, and then placed in a molybdenum / zirconium / niobium metal cup for high temperature and high pressure, and the diamond layer is subjected to heat debinding and raw material purification treatment, the heat debinding process is room temperature to 600-650℃, the heating rate is 0.5-2℃ / min, to remove the organic polymer skeleton; the raw material purification process is 900-1000℃ vacuum heat treatment for 1-2h, the heating rate is 2-5℃ / min, (7) high temperature and high pressure sintering: the diamond-hard alloy combined structure in step (6) is placed in the metal cup, and the salt tube, graphite tube and talc tube are assembled layer by layer from inside to outside, to obtain a high temperature and high pressure synthesis block, and then placed in a hexahedral press for high temperature and high pressure synthesis, to obtain a spiral structure PCD cutter bit.

2. A process for additive manufacturing of a polycrystalline diamond-cemented carbide solid helical cutter according to claim 1, characterized in that: The pressure of the high temperature and high pressure treatment is 6~8GPa, and the temperature is 1450~1550℃.

3. A process for additive manufacturing of a polycrystalline diamond-cemented carbide solid helical cutter according to claim 1, characterized in that: The raw material diamond used has a particle size of A: particle size of B = 60~80:40~20 by mass ratio; the value of A is 8~20 microns, and the value of B is less than or equal to 3 microns.

4. A process for additive manufacturing of a polycrystalline diamond-cemented carbide solid helical cutter according to claim 1, characterized in that: In step (1), when preparing the diamond feeding, the mass ratio of diamond to binder is 93-97:3-7; the powder loading of diamond+binder is 50-55vol.%.

5. A process for additive manufacturing of a polycrystalline diamond-cemented carbide solid helical cutter according to claim 1, characterized in that: In step (1), the filler is composed of solid paraffin and microcrystalline wax in a mass ratio of 40-50:15-20; the skeleton is composed of high-density polyethylene and ethylene-vinyl acetate copolymer in a mass ratio of 20-25:10-15; the plasticizer is dioctyl phthalate; and the surfactant is stearic acid.

6. A process for additive manufacturing of a polycrystalline diamond-cemented carbide solid helical cutter according to claim 1, characterized in that: In step (2), the filler is composed of solid paraffin and microcrystalline wax in a mass ratio of 40-50:10-40; the skeleton is composed of high-density polyethylene and ethylene-vinyl acetate copolymer in a mass ratio of 10-30:10-30; the plasticizer is dioctyl phthalate; and the surface active agent is stearic acid.

7. A process for additive manufacturing of a polycrystalline diamond-cemented carbide solid helical cutter according to claim 1, characterized in that: The particle size of the diamond printing feed is 8-20 mesh; and the particle size of the cemented carbide printing feed is 8-20 mesh.

8. A process for additive manufacturing of a polycrystalline diamond-cemented carbide solid helical cutter according to claim 1, characterized in that: In step (7), the synthesis process is pressure: 5.5-7.5 GPa, temperature: 1400-1700 ℃.

Images