High-wear-resistance hard alloy mirror-polished plate and preparation method thereof

Abstract

The present application relates to the technical field of alloy, in particular to a high wear-resistant hard alloy mirror polishing plate and a preparation method thereof.The present application realizes directional and nanoscale uniform coating of grain growth inhibitor on the surface of tungsten carbide particles by surface activation of tungsten carbide powder, treatment with vanadium-containing solution and chromium source solution in sequence, formation of layered precursor with internal vanadium and external chromium, and precise segmented cooling process after pre-heat preservation and pressure sintering in liquid phase, so that the hard alloy mirror polishing plate with high hardness, high strength, low surface roughness / waviness and excellent long-term wear resistance is obtained.

Description

Technical Field

[0001] This invention relates to the field of alloy technology, and in particular to a high wear-resistant hard alloy mirror polishing sheet and its preparation method. Background Technology

[0002] Due to its excellent hardness, wear resistance, and compressive strength, cemented carbide is widely used in key fields such as precision molds, cutting tools, and wear-resistant seals. Among them, large-size cemented carbide sheets, after high-precision polishing, can serve as core optical platforms and carriers in high-value-added fields such as optics, semiconductor manufacturing, and high-precision measurement. Its surface quality and service life directly determine the accuracy and reliability of the end products.

[0003] In existing technologies, to achieve high hardness, high wear resistance, and good mirror polishing effect, methods such as refining tungsten carbide grains, adding grain growth inhibitors (such as VC, Cr3C2, etc.), and optimizing sintering processes are commonly used. However, these conventional methods often face irreconcilable contradictions when synergistically improving the overall performance of the sheet material.

[0004] Firstly, in pursuing high hardness and high wear resistance, methods such as increasing cobalt content or adding various inhibitors are usually adopted. However, excessive cobalt content will reduce the elastic modulus and high-temperature performance of the alloy, while the uneven distribution of inhibitors can easily form coarse and brittle phases or abnormal local grain growth in the microstructure. Although this can improve some wear resistance indicators, it often comes at the cost of sacrificing the transverse fracture strength and impact toughness of the material, making the plate prone to brittle fracture under complex stress conditions.

[0005] Secondly, the uniformity of the material's microstructure is a decisive factor in achieving excellent mirror-like finish. Traditional mixing and sintering processes struggle to achieve a uniform and orderly nanoscale distribution of inhibitors among tungsten carbide grains. During the subsequent high-temperature liquid-phase sintering stage, inhibitor elements (such as vanadium and chromium) are prone to uncontrolled long-range diffusion and segregation, forming a second phase or grain boundary phase with uneven size, morphology, and distribution within the matrix. This microstructural inhomogeneity exacerbates the selective grinding effect during subsequent ultra-precision polishing due to differences in hardness and wear resistance between the "phase" and the "matrix." This manifests as microscopic "pits" or "protrusions" on the polished surface, making it difficult to achieve surface roughness and waviness down to the nanometer level, and resulting in poor in-plane roughness consistency, thus affecting optical functionality.

[0006] Furthermore, in terms of thermal process control, existing processes mostly focus on the densification stage, with insufficient control over the pretreatment of the sintering precursor and the cooling process after liquid phase formation. This results in a large amount of internal stress between tungsten carbide grains in the final product, and the grain boundary structure cannot be effectively optimized. Under long-term abrasive wear or continuous sliding friction conditions, these potential defects will accelerate crack initiation and propagation, manifesting as a rapid decline in wear resistance, especially resistance to high-stress friction and wear, which does not match the initial high hardness index and restricts the service life of high-end precision components.

[0007] Therefore, how to start from the source of material preparation and, through innovative process design, ensure the high hardness and high strength of cemented carbide while achieving a highly uniform, stable, and controllable microstructure, thereby synergistically obtaining excellent mirror polishing performance and long-term stable high wear resistance, has become a core technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] In view of this, the purpose of this invention is to provide a high wear-resistant cemented carbide mirror polishing sheet and its preparation method, so as to solve the problem that the existing cemented carbide sheet preparation technology is difficult to achieve high hardness, high strength and extremely low mirror roughness and waviness, and its wear resistance stability is insufficient after high-precision polishing, which restricts its application in ultra-precision optical and semiconductor equipment.

[0009] To achieve the above objectives, the present invention provides a high wear-resistant cemented carbide mirror polished sheet material, comprising a cemented carbide substrate, wherein the cemented carbide substrate contains tungsten carbide and cobalt, and at least one surface of the cemented carbide substrate is a mirror polished surface.

[0010] The raw materials for preparing the high wear-resistant cemented carbide mirror polishing sheet, by weight, include: 268-274 parts tungsten carbide powder, 28-33 parts cobalt powder, 0.40-0.65 parts carbon black, 1.8-3.0 parts ammonium metavanadate, 2.5-3.8 parts oxalic acid dihydrate, 0.9-1.6 parts chromium nitrate nonahydrate, and 3-5 parts polyvinyl alcohol;

[0011] The high wear-resistant cemented carbide mirror polished sheet is prepared by the following method: after surface activation of the tungsten carbide powder, it is first treated with a vanadium-containing solution formed by ammonium metavanadate and oxalic acid dihydrate, then treated with a chromium source solution formed by chromium nitrate nonahydrate, and then heat-treated to obtain composite tungsten carbide powder; the composite tungsten carbide powder is mixed with cobalt powder and carbon black, pressed, preheated before liquid phase formation, pressure sintered and segmented cooled, and then mirror polished to obtain the high wear-resistant cemented carbide mirror polished sheet.

[0012] Preferably, the tungsten carbide powder has an average particle size of 350 nm, and the cobalt powder has an average particle size of 1.6 μm.

[0013] Preferably, the surface activation is performed by adding the tungsten carbide powder to anhydrous ethanol and deionized water, mechanically stirring at 8-15°C for 12-20 min, then adding a 30% hydrogen peroxide solution by mass, continuing stirring for 10-15 min, followed by washing with anhydrous ethanol and vacuum drying to obtain surface-activated tungsten carbide powder.

[0014] Preferably, the vanadium-containing solution is added to the surface-activated tungsten carbide powder by atomization spraying, and the chromium source solution is sprayed into the resulting powder in three stages to form a layered precursor in which the vanadium-containing component is located in the inner layer and the chromium-containing component is located in the outer layer relative to the surface of the tungsten carbide particles before heat treatment.

[0015] Preferably, the heat treatment is carried out in an argon-hydrogen mixed atmosphere and includes: heating to 430-470°C at 2°C / min and holding for 50-75 min, then heating to 860-900°C at 3°C / min and holding for 30-50 min, followed by furnace cooling.

[0016] Preferably, the preheating, pressurized sintering, and segmented cooling before liquid phase formation include: first, heating to 1180-1220℃ at 2.5-3.5℃ / min and holding for 30-50min; then heating to 1365-1380℃ at 4.5-5.5℃ / min and holding for 20-28min; then introducing 4-6MPa argon gas at 1355-1365℃ and holding for 15-25min; then cooling to 1260-1290℃ at 30-40℃ / min; then cooling to 1080-1120℃ at 8-12℃ / min; and finally cooling to room temperature with the furnace.

[0017] Preferably, the volume fraction of hydrogen in the argon-hydrogen mixture is 5%, and the mirror-polished surface is formed by sequential double-sided fine grinding with 15μm and 6μm diamond grinding discs, followed by sequential polishing with 3μm, 1μm and 0.25μm polycrystalline diamond suspensions.

[0018] Furthermore, the present invention also provides a method for preparing a high wear-resistant cemented carbide mirror polishing sheet, comprising the following steps:

[0019] (1) Surface-activate tungsten carbide powder to obtain surface-activated tungsten carbide powder;

[0020] (2) Prepare a vanadium-containing solution by mixing ammonium metavanadate and oxalic acid dihydrate, and spray the vanadium-containing solution onto the surface-activated tungsten carbide powder and dry it;

[0021] (3) Chromium nitrate nonahydrate is prepared into a chromium source solution, and the chromium source solution is sprayed onto the powder obtained in step (2), dried and then heat-treated to obtain composite tungsten carbide powder;

[0022] (4) The composite tungsten carbide powder is mixed with cobalt powder and carbon black and wet-milled, dried, ground and sieved to obtain pressed particles;

[0023] (5) Press the pressed particles into a slab;

[0024] (6) The slab is preheated before liquid phase formation, pressurized and sintered and then cooled in stages to obtain sintered slab;

[0025] (7) The sintered plate is subjected to double-sided fine grinding and mirror polishing to obtain a high wear-resistant hard alloy mirror polished plate.

[0026] Preferably, in step (5), the pressed particles obtained in step (4) are placed into a rectangular mold, unidirectionally pressed at 70-90MPa, and then cold isostatically pressed at 200-240MPa for 2.5-3.5min to obtain a slab.

[0027] The beneficial effects of this invention are:

[0028] (1) This invention achieves directional, nanoscale uniform coating of grain growth inhibitors on the surface of tungsten carbide particles by surface activation of tungsten carbide powder, layered fixation of vanadium / chromium precursors, and dual-carbon timing control. This structure effectively inhibits abnormal grain growth during subsequent sintering, forming a fine and uniform microstructure. This is the key to achieving simultaneous improvement in high hardness (Rockwell A hardness of 92.5 or higher) and high transverse fracture strength (3800 MPa or higher) of the plate, providing a uniform substrate material for subsequent mirror polishing.

[0029] (2) Thanks to the highly uniform microstructure described above, the substrate prepared by this invention exhibits excellent surface quality after fine grinding and polishing. Example data shows that its surface roughness Ra can be as low as 0.014 μm, its waviness Wa as low as 0.032 μm, and its in-plane surface roughness uniformity is high (9-point Ra standard deviation ≤ 0.003 μm). This indicates that the material possesses excellent polishability and dimensional stability at the nanoscale, meeting the stringent requirements of ultra-precision optical platforms for surface morphology.

[0030] (3) This invention optimizes the grain boundary structure and residual stress distribution by precisely controlling the thermal process of pre-liquid phase heat preservation and segmented cooling. This synergistic effect significantly improves the wear resistance stability of the material under harsh working conditions. Tests show that the volumetric wear amount ΔV1 of the plate can reach as low as 0.593 mm in both abrasive wear and continuous contact sliding friction wear. 3 Compared with the comparative sample prepared by conventional process, the overall wear resistance is improved by more than 40%. This solves the problem of mismatch between the wear resistance life and the initial hardness index of traditional high hardness cemented carbide mirror panels in precision service, and greatly expands its application potential in high-load, long-life precision equipment. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0032] The raw materials used are as follows: tungsten carbide powder with an average particle size of 350 nm; cobalt powder with an average particle size of 1.6 μm; polyvinyl alcohol, type 1799; and hydrogen gas fraction of 5% in the argon-hydrogen mixture.

[0033] Example 1:

[0034] Step 1: Take 270g of tungsten carbide powder and add it to 180g of anhydrous ethanol and 40g of deionized water. Stir mechanically at 10℃ for 15min to fully wet and disperse the powder. Then slowly add 8g of 30% hydrogen peroxide solution and continue stirring for 12min. After the treatment, wash once with 60g of anhydrous ethanol and vacuum dry at 60℃ for 4h to obtain surface-activated tungsten carbide powder.

[0035] Step 2: Take 2.4g of ammonium metavanadate and 3g of oxalic acid dihydrate and add them to 30g of deionized water. Stir at 70℃ until the solution is clear. Add the vanadium-containing solution evenly to the surface-activated tungsten carbide powder obtained in Step 1 by atomization spraying. Stir continuously at 60℃. After the spraying is completed, continue stirring for 30min. Then dry at 80℃ for 2h.

[0036] Step 3: Take 1.2g of chromium nitrate nonahydrate and add it to 15g of deionized water to prepare a chromium source solution; spray the chromium source solution into the powder obtained in Step 2 in three parts at 50℃, stirring for 5min after each spraying, and dry at 80℃ for 2h after the spraying is completed; place the dried powder in an argon-hydrogen mixed atmosphere, heat it to 450℃ at 2℃ / min and hold it for 1h, then heat it to 880℃ at 3℃ / min and hold it for 40min, and then cool it with the furnace to obtain composite tungsten carbide powder;

[0037] Step 4: Add the composite tungsten carbide powder obtained in Step 3, 30g of cobalt powder, 0.5g of carbon black, and 160g of anhydrous ethanol to a cemented carbide ball mill jar, then add 900g of cemented carbide balls, and wet mill for 5 hours under argon protection; separately, add 4g of polyvinyl alcohol to 80g of deionized water, stir at 90℃ until completely dissolved, cool to 40℃, and then add to the above ball mill slurry and continue wet milling for 1 hour; after ball milling, vacuum dry at 55℃, grind and pass through a 60-mesh sieve to obtain pressed particles;

[0038] Step 5: Take 300g of the pressed granules obtained in Step 4 and put them into a rectangular mold. Press them unidirectionally at 80MPa and then cold isostatically press them at 220MPa for 3 minutes to obtain a slab with dimensions of 122mm×61mm×4.8mm.

[0039] Step 6: Place the slab obtained in Step 5 into a sintering furnace. First, introduce an argon-hydrogen mixture, raise the temperature to 200℃ at 1℃ / min and hold for 30min, then raise the temperature to 450℃ at 0.5℃ / min and hold for 60min. Then, evacuate to below 5Pa, raise the temperature to 1200℃ at 3℃ / min and hold for 40min, raise the temperature to 1370℃ at 5℃ / min and hold for 25min, then introduce 5MPa argon at 1360℃ and hold for 20min. After that, lower the temperature to 1280℃ at 35℃ / min, then lower the temperature to 1100℃ at 10℃ / min, and finally cool it to room temperature with the furnace to obtain the sintered slab.

[0040] Step 7: The sintered plate obtained in Step 6 is sequentially double-sided finely ground using 15μm and 6μm diamond grinding discs, with the total removal amount on both sides controlled to 120μm; then, it is sequentially polished using 3μm, 1μm and 0.25μm polycrystalline diamond suspensions respectively, to obtain a high wear-resistant cemented carbide mirror polished plate with dimensions of 100mm×50mm×4mm.

[0041] Example 2:

[0042] Step 1: Take 268g of tungsten carbide powder and add it to 170g of anhydrous ethanol and 35g of deionized water. Stir mechanically at 8℃ for 12min to fully wet and disperse the powder. Then slowly add 6g of 30% hydrogen peroxide solution and continue stirring for 10min. After the treatment, wash once with 50g of anhydrous ethanol and vacuum dry at 55℃ for 3.5h to obtain surface-activated tungsten carbide powder.

[0043] Step 2: Take 1.8g of ammonium metavanadate and 2.5g of oxalic acid dihydrate and add them to 25g of deionized water. Stir at 65℃ until the solution is clear. Add the resulting vanadium-containing solution evenly to the surface-activated tungsten carbide powder obtained in Step 1 by atomization spraying. Stir continuously at 55℃. After the spraying is completed, continue stirring for 20min. Then dry at 75℃ for 1.5h.

[0044] Step 3: Take 0.9g of chromium nitrate nonahydrate and add it to 12g of deionized water to prepare a chromium source solution; spray the chromium source solution into the powder obtained in Step 2 in three parts at 45℃, stirring for 5min after each spraying, and dry at 75℃ for 1.5h after the spraying is completed; place the dried powder in an argon-hydrogen mixed atmosphere, heat it to 430℃ at 2℃ / min and hold it for 50min, then heat it to 860℃ at 3℃ / min and hold it for 30min, and then cool it with the furnace to obtain composite tungsten carbide powder;

[0045] Step 4: Add the composite tungsten carbide powder obtained in Step 3, 28g of cobalt powder, 0.40g of carbon black, and 150g of anhydrous ethanol to a cemented carbide ball mill jar, then add 850g of cemented carbide balls, and wet mill for 4.5h under argon protection; separately, add 3g of polyvinyl alcohol to 70g of deionized water, stir at 85℃ until completely dissolved, cool to 35℃, and then add to the above ball mill slurry and continue wet milling for 0.8h; after ball milling, vacuum dry at 50℃, grind and pass through a 60-mesh sieve to obtain pressed particles;

[0046] Step 5: Take 300g of the pressed granules obtained in Step 4 and put them into a rectangular mold. Press them unidirectionally at 70MPa and then cold isostatically press them at 200MPa for 2.5min to obtain a slab with dimensions of 122mm×61mm×4.7mm.

[0047] Step 6: Place the slab obtained in Step 5 into a sintering furnace. First, introduce an argon-hydrogen mixture, raise the temperature to 180℃ at 0.8℃ / min and hold for 25 min, then raise the temperature to 430℃ at 0.4℃ / min and hold for 50 min. Then, evacuate to below 5 Pa, raise the temperature to 1180℃ at 2.5℃ / min and hold for 30 min, then raise the temperature to 1365℃ at 4.5℃ / min and hold for 20 min. Then, introduce 4 MPa argon at 1355℃ and hold for 15 min. After that, lower the temperature to 1260℃ at 30℃ / min, then lower the temperature to 1080℃ at 8℃ / min, and finally cool it to room temperature with the furnace to obtain the sintered slab.

[0048] Step 7: The sintered plate obtained in Step 6 is sequentially double-sided finely ground using 15μm and 6μm diamond grinding discs, with the total removal amount on both sides controlled to 100μm; then, it is sequentially polished using 3μm, 1μm and 0.25μm polycrystalline diamond suspensions respectively, to obtain a high wear-resistant cemented carbide mirror polished plate with dimensions of 100mm×50mm×4mm.

[0049] Example 3:

[0050] Step 1: Take 272g of tungsten carbide powder and add it to 185g of anhydrous ethanol and 42g of deionized water. Stir mechanically at 12℃ for 18min to fully wet and disperse the powder. Then slowly add 9g of 30% hydrogen peroxide solution and continue stirring for 14min. After the treatment, wash once with 65g of anhydrous ethanol and vacuum dry at 62℃ for 4.2h to obtain surface-activated tungsten carbide powder.

[0051] Step 2: Take 2.8g of ammonium metavanadate and 3.4g of oxalic acid dihydrate and add them to 32g of deionized water. Stir at 72℃ until the solution is clear. Add the resulting vanadium-containing solution evenly to the surface-activated tungsten carbide powder obtained in Step 1 by atomization spraying. Stir continuously at 62℃. After the spraying is completed, continue stirring for 35min. Then dry at 82℃ for 2.2h.

[0052] Step 3: Take 1.4g of chromium nitrate nonahydrate and add it to 16g of deionized water to prepare a chromium source solution; spray the chromium source solution into the powder obtained in Step 2 in three parts at 52℃, stirring for 5min after each spraying, and dry at 82℃ for 2.2h after the spraying is completed; place the dried powder in an argon-hydrogen mixed atmosphere, heat it to 460℃ at 2℃ / min and hold it for 65min, then heat it to 890℃ at 3℃ / min and hold it for 45min, and then cool it with the furnace to obtain composite tungsten carbide powder;

[0053] Step 4: Add the composite tungsten carbide powder obtained in Step 3, 31g of cobalt powder, 0.55g of carbon black, and 165g of anhydrous ethanol to a cemented carbide ball mill jar, then add 930g of cemented carbide balls, and wet mill for 5.2h under argon protection; separately, add 4.5g of polyvinyl alcohol to 85g of deionized water, stir at 92℃ until completely dissolved, cool to 42℃, and then add to the above ball mill slurry and continue wet milling for 1.1h; after ball milling, vacuum dry at 58℃, grind and pass through a 60-mesh sieve to obtain pressed particles;

[0054] Step 5: Take 300g of the pressed granules obtained in Step 4 and put them into a rectangular mold. Press them unidirectionally at 85MPa and then cold isostatically press them at 230MPa for 3.2min to obtain a slab with dimensions of 122mm×61mm×4.85mm.

[0055] Step 6: Place the slab obtained in Step 5 into a sintering furnace. First, introduce an argon-hydrogen mixture, raise the temperature to 210℃ at 1.1℃ / min and hold for 32 min, then raise the temperature to 460℃ at 0.55℃ / min and hold for 65 min. Then, evacuate to below 5 Pa, raise the temperature to 1210℃ at 3.2℃ / min and hold for 45 min, raise the temperature to 1375℃ at 5.2℃ / min and hold for 26 min, then introduce 5 MPa argon at 1360℃ and hold for 20 min. After that, lower the temperature to 1285℃ at 36℃ / min, then lower the temperature to 1100℃ at 10℃ / min, and finally cool it to room temperature with the furnace to obtain the sintered slab.

[0056] Step 7: The sintered plate obtained in Step 6 is sequentially double-sided finely ground using 15μm and 6μm diamond grinding discs, with the total removal amount on both sides controlled to 130μm; then, it is sequentially polished using 3μm, 1μm and 0.25μm polycrystalline diamond suspensions respectively, to obtain a high wear-resistant cemented carbide mirror polished plate with dimensions of 100mm×50mm×4mm.

[0057] Example 4:

[0058] Step 1: Take 274g of tungsten carbide powder and add it to 190g of anhydrous ethanol and 45g of deionized water. Stir mechanically at 15℃ for 20min to fully wet and disperse the powder. Then slowly add 10g of 30% hydrogen peroxide solution and continue stirring for 15min. After the treatment, wash once with 70g of anhydrous ethanol and vacuum dry at 65℃ for 4.5h to obtain surface-activated tungsten carbide powder.

[0059] Step 2: Take 3.0g of ammonium metavanadate and 3.8g of oxalic acid dihydrate and add them to 35g of deionized water. Stir at 75℃ until the solution is clear. Add the resulting vanadium-containing solution evenly to the surface-activated tungsten carbide powder obtained in Step 1 by atomization spraying. Stir continuously at 65℃. After the spraying is completed, continue stirring for 40min. Then dry at 85℃ for 2.5h.

[0060] Step 3: Take 1.6g of chromium nitrate nonahydrate and add it to 18g of deionized water to prepare a chromium source solution; spray the chromium source solution into the powder obtained in Step 2 in three parts at 55℃, stirring for 5min after each spraying, and dry at 85℃ for 2.5h after the spraying is completed; place the dried powder in an argon-hydrogen mixed atmosphere, heat it to 470℃ at 2℃ / min and hold it for 75min, then heat it to 900℃ at 3℃ / min and hold it for 50min, and then cool it with the furnace to obtain composite tungsten carbide powder;

[0061] Step 4: Add the composite tungsten carbide powder obtained in Step 3, 33g of cobalt powder, 0.65g of carbon black, and 170g of anhydrous ethanol to a cemented carbide ball mill jar, then add 950g of cemented carbide balls, and wet mill for 5.5h under argon protection; separately, add 5g of polyvinyl alcohol to 90g of deionized water, stir at 95℃ until completely dissolved, cool to 45℃, and then add to the above ball mill slurry and continue wet milling for 1.2h; after ball milling, vacuum dry at 60℃, grind and pass through a 60-mesh sieve to obtain pressed particles;

[0062] Step 5: Take 300g of the pressed granules obtained in Step 4 and put them into a rectangular mold. Press them unidirectionally at 90MPa and then cold isostatically press them at 240MPa for 3.5min to obtain a slab with dimensions of 122mm×61mm×4.9mm.

[0063] Step 6: Place the slab obtained in Step 5 into a sintering furnace. First, introduce an argon-hydrogen mixture, raise the temperature to 220℃ at 1.2℃ / min and hold for 35min, then raise the temperature to 470℃ at 0.6℃ / min and hold for 70min. Then, evacuate to below 5Pa, raise the temperature to 1220℃ at 3.5℃ / min and hold for 50min, then raise the temperature to 1380℃ at 5.5℃ / min and hold for 28min. Then, introduce 6MPa argon at 1365℃ and hold for 25min. After that, lower the temperature to 1290℃ at 40℃ / min, then lower the temperature to 1120℃ at 12℃ / min, and finally cool it to room temperature with the furnace to obtain the sintered slab.

[0064] Step 7: The sintered plate obtained in Step 6 is sequentially double-sided finely ground using 15μm and 6μm diamond grinding discs, with the total removal amount on both sides controlled to 140μm; then, it is sequentially polished using 3μm, 1μm and 0.25μm polycrystalline diamond suspensions respectively, to obtain a high wear-resistant cemented carbide mirror polished plate with dimensions of 100mm×50mm×4mm.

[0065] Comparative Example 1:

[0066] The difference from Example 1 is that in step 1, 8g of 30% hydrogen peroxide solution is not added, but instead an equal mass of deionized water is used; the other conditions are the same as in Example 1.

[0067] Comparative Example 2:

[0068] The difference from Example 1 is that: in step 2, ammonium metavanadate is not added, but only 3g of oxalic acid dihydrate is added to 30g of deionized water and sprayed onto the surface-activated tungsten carbide powder obtained in step 1; at the same time, in step 4, 2.4g of ammonium metavanadate, together with the powder obtained in step 3, 30g of cobalt powder, 0.5g of carbon black and 160g of anhydrous ethanol, are added to the cemented carbide ball mill jar; the other conditions are the same as in Example 1.

[0069] Comparative Example 3:

[0070] The difference from Example 1 is that in step 2, 2.4g of ammonium metavanadate, 3g of oxalic acid dihydrate and 1.2g of chromium nitrate nonahydrate are added together to 30g of deionized water to prepare a mixed solution, which is then sprayed onto the surface-activated tungsten carbide powder obtained in step 1 in one go; in step 3, the chromium nitrate nonahydrate is no longer sprayed separately, and only drying and subsequent heat treatment are performed; the other conditions are the same as in Example 1.

[0071] Comparative Example 4:

[0072] The difference from Example 1 is that 1.2g of chromium nitrate nonahydrate is not added in step 3; in order to keep the total solid feed amount consistent, 1.2g of tungsten carbide powder is added in step 4; the other conditions are the same as in Example 1.

[0073] Comparative Example 5:

[0074] The difference from Example 1 is that: 3g of oxalic acid dihydrate is not added in step 2; the amount of carbon black added in step 4 is adjusted from 0.5g to 1.07g to make up for the amount of carbon supplied by the oxalic acid dihydrate according to the theoretical carbon element mass; the other conditions are the same as in Example 1.

[0075] Comparative Example 6:

[0076] The difference from Example 1 is that in step 6, the temperature is directly increased from 450℃ to 1370℃ at a rate of 3℃ / min and held for 25 minutes, instead of being held at 1200℃ for 40 minutes; the other conditions are the same as in Example 1.

[0077] Comparative Example 7:

[0078] The difference from Example 1 is that in step 6, after introducing 5MPa argon gas at 1360℃ and holding it at that temperature for 20 minutes, the furnace is directly cooled to room temperature. The segmented cooling procedure of cooling down to 1280℃ at 35℃ / min and then to 1100℃ at 10℃ / min is no longer performed. The other conditions are the same as in Example 1.

[0079] Performance test sample preparation and sampling:

[0080] In addition to preparing mirror-polished sheets with dimensions of 100mm × 50mm × 4mm, each embodiment and comparative example also included an auxiliary test blank with dimensions of 110mm × 20mm × 8mm, used for processing standard specimens for transverse fracture strength. Density, Rockwell A hardness, surface roughness, surface waviness, abrasive wear, and continuous contact sliding friction wear specimens were all taken from the central area of ​​the 100mm × 50mm × 4mm mirror-polished sheet, avoiding the area within 5mm of the edge; transverse fracture strength specimens were obtained from the same batch of auxiliary test blanks. Abrasive wear specimens were processed into 50mm × 25mm × 4mm flat plates, and continuous contact sliding friction wear specimens were processed into 20mm × 20mm × 4mm flat plates; all wear-resistant specimens were ultrasonically cleaned in anhydrous ethanol for 10 min before testing, dried at 60℃ for 30 min, and their initial mass was measured using an analytical balance with an accuracy of 0.01mg. Each group of samples had at least three parallel samples, with density and hardness measured at least five times, and the results are expressed as average values.

[0081] Performance testing:

[0082] Density: The density was determined according to the Archimedes method in accordance with GB / T 3850-2015.

[0083] Rockwell A hardness: Rockwell A hardness was determined according to GB / T 3849.1-2015.

[0084] Transverse fracture strength: Transverse fracture strength was tested using type A specimens in accordance with GB / T 3851-2015. The three-point bending span was set to 30 mm, the loading head was located at the midpoint of the span, and the loading speed was set to 1 mm / min. The fracture load was recorded and the transverse fracture strength was calculated according to the standard formula.

[0085] Surface roughness: Surface roughness was tested according to GB / T 1031-2009, GB / T 3505-2009, and GB / T 10610-2009. A 3×3 measuring point matrix was established on the surface of each mirror panel using a contact profilometer, with a total of 9 measuring points. The measurement length of each measuring point was 4 mm, the sampling length was 0.8 mm, the stylus tip radius was 2 μm, and the measurement speed was 0.5 mm / s. The test was performed once along the length and once along the width of the panel, and Ra and Rz were obtained. The average value of the two directions was taken as the result of the measuring point. For each sample, the average value and standard deviation of Ra at the 9 points were further calculated. The average value of Ra was used to characterize the fineness of the mirror surface, and the standard deviation of Ra at the 9 points was used to characterize the in-plane uniformity of the mirror surface.

[0086] Surface waviness: The surface waviness was tested according to the terminology for surface waviness in GB / T 16747-2009 and the evaluation rules in GB / T10610-2009. A contact profilometer, the same type used for surface roughness, was employed. Three measurement lines were selected along the length of the plate: the center line and two equidistant lines on both sides. Each measurement line was 15 mm long, with an evaluation length of 12.5 mm and a cutoff wavelength of 2.5 mm. Wa and Wt were measured. Each sample was tested three times, and the average value was taken as the final result.

[0087] Abrasive wear performance: Abrasive wear tests were conducted according to GB / T 34501-2017. The sample size was 50mm × 25mm × 4mm. A dry abrasive wear mode using a rubber wheel was employed. The rubber wheel diameter was 228.6mm, the wheel surface width was 12.7mm, and the wheel surface hardness was Shore A 60±2. The abrasive used was dry quartz sand with a particle size of 180μm-250μm and a moisture content controlled below 1%. The test load was 130N, the wheel speed was 200r / min, and the total number of revolutions was 6000rev. The sample masses m0 and m1 were weighed before and after the test, and the volumetric wear amount ΔV1 was calculated based on the density test results. Three parallel samples were tested for each group of samples.

[0088] Continuous contact sliding friction and wear performance: Pin-disc sliding friction and wear test was conducted according to YB / T 6178-2024. A 20mm×20mm×4mm mirror panel was fixed as a disc sample and matched with a GCr15 steel pin with an end face diameter of 6mm. The test was conducted under the conditions of 23℃±2℃, relative humidity 50%±10%, load of 50N, linear velocity of 0.20m / s, grinding rail radius of 5mm, and total sliding distance of 1000m. The friction coefficient curve was continuously recorded during the test, and the average friction coefficient of the last 200m interval was taken as the steady-state friction coefficient.

[0089] The test results are shown in Table 1.

[0090] Table 1 Performance Test Results

[0091] sample <![CDATA[Density / (g / cm 3 )]]> Rockwell A hardness Transverse fracture strength (MPa) Ra / (μm) Rz / (μm) 9-point Ra standard deviation / (μm) Wa / (μm) Wt / (μm) <![CDATA[Volume wear loss ΔV1 / (mm 3 )]]> steady-state friction coefficient Example 1 14.40 92.8 3940 0.017 0.104 0.002 0.040 0.297 0.724 0.364 Example 2 14.46 92.6 3810 0.021 0.126 0.003 0.047 0.348 0.846 0.388 Example 3 14.36 92.9 4060 0.014 0.086 0.002 0.032 0.238 0.593 0.346 Example 4 14.30 92.5 3900 0.015 0.094 0.003 0.036 0.266 0.649 0.354 Comparative Example 1 14.35 91.9 3460 0.034 0.224 0.006 0.070 0.528 1.312 0.438 Comparative Example 2 14.37 92.1 3550 0.030 0.197 0.005 0.063 0.468 1.108 0.416 Comparative Example 3 14.38 92.2 3650 0.026 0.169 0.004 0.055 0.411 0.981 0.401 Comparative Example 4 14.40 92.4 3750 0.023 0.149 0.004 0.050 0.377 0.908 0.391 Comparative Example 5 14.38 92.2 3690 0.025 0.159 0.004 0.053 0.396 0.944 0.396 Comparative Example 6 14.39 92.2 3620 0.028 0.182 0.005 0.058 0.434 1.027 0.408 Comparative Example 7 14.39 92.1 3590 0.029 0.191 0.005 0.061 0.456 1.082 0.421

[0092] As can be seen from Table 1, the densities of each embodiment and comparative example of this application are all within the reasonable range of fine-grained / ultra-fine-grained WC-Co cemented carbide. However, the density does not correspond to the overall performance in a simple linear manner. This is because the amount of Co and VC / Cr inhibitor added in Examples 2 to 4 is different, and the theoretical density itself is different. In terms of overall performance, Example 1 has optimized the Rockwell A hardness, transverse fracture strength, mirror roughness and wear resistance of the plate simultaneously by means of surface activation, vanadium-containing precursor layer orientation fixation, outer chromium source post-spraying, pre-carbon supply / post-carbon replenishment, liquid phase pre-heating and segmented cooling.

[0093] Compared with Comparative Example 1, the Rockwell A hardness of Example 1 increased from 91.9 to 92.8, the transverse fracture strength increased from 3460 MPa to 3940 MPa, Ra decreased from 0.03 μm to 0.017 μm, and the volumetric wear amount ΔV1 decreased from 1.312 mm. 3 Reduced to 0.724mm 3 This indicates that mirror finish quality and service wear resistance can only be improved simultaneously when the WC surface is first activated and provides interface conditions for subsequent inhibitor layering and fixation.

[0094] Compared with Comparative Examples 2 and 3, Examples 1 and 3 further demonstrate that fixing ammonium metavanadate to the outer edge of WC particles before introducing the chromium source is superior to the treatment method of post-mixing the vanadium component or spraying vanadium and chromium together in one step. Among them, Example 3 has the best overall performance, with a Rockwell A hardness of 92.9, a transverse fracture strength of 4060 MPa, and Ra, Rz, 9-point Ra standard deviation, Wa, and Wt reduced to 0.014 μm, 0.086 μm, 0.002 μm, 0.032 μm, and 0.238 μm, respectively. The volumetric wear amount ΔV1 and the steady-state friction coefficient were further reduced to 0.593 mm. 3The values ​​of 0.346 indicate that by appropriately increasing the amount of vanadium-containing layer and outer chromium source, and combining this with preheating before liquid phase and segmented cooling, abnormal grain agglomeration, in-plane structural abrupt changes, and mirror ripples can be significantly reduced while maintaining high strength and high hardness.

[0095] Further analysis of Comparative Examples 4 and 5 reveals that omitting the chromium source post-layer or eliminating the pre-carbon supply and relying solely on post-carbon replenishment will reduce strength, mirror uniformity, and wear resistance to varying degrees. Comparative Examples 6 and 7 show that even with essentially the same chemical composition, eliminating the 1200℃ heat preservation or segmented cooling significantly degrades Ra, Wa, Wt, volumetric wear ΔV1, and steady-state friction coefficient, indicating that thermal history control plays a crucial role in maintaining the short-range distribution structure and suppressing random diffusion in the liquid phase.

[0096] It should be noted that although Example 4 still maintains a low Ra, Wa and wear amount, its Rockwell A hardness and transverse fracture strength are slightly lower than those of Example 3, indicating that the inhibitor and Co content is not necessarily better the higher it is, and there is a better synergistic window.

[0097] In summary, this application does not rely on the single crystal-inhibiting effect of VC or Cr, but rather achieves high hardness, high transverse fracture strength, low mirror roughness and waviness, and better abrasive wear and continuous contact sliding friction wear performance by means of surface activation, vanadium / chromium layer positioning, dual carbon timing regulation and synergistic thermal history before and after liquid phase.

[0098] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A mirror-polished plate of high wear-resistant cemented carbide, characterized in that, It includes a cemented carbide substrate containing tungsten carbide and cobalt, and at least one surface of the cemented carbide substrate is a mirror-polished surface; The raw materials for preparing the high wear-resistant cemented carbide mirror polishing sheet, by weight, include: 268-274 parts tungsten carbide powder, 28-33 parts cobalt powder, 0.40-0.65 parts carbon black, 1.8-3.0 parts ammonium metavanadate, 2.5-3.8 parts oxalic acid dihydrate, 0.9-1.6 parts chromium nitrate nonahydrate, and 3-5 parts polyvinyl alcohol; The high wear-resistant cemented carbide mirror polished sheet is prepared by the following method: After surface activation of the tungsten carbide powder, it is first treated with a vanadium-containing solution formed by ammonium metavanadate and oxalic acid dihydrate, then treated with a chromium source solution formed by chromium nitrate nonahydrate, and finally heat-treated to obtain composite tungsten carbide powder; the composite tungsten carbide powder is mixed with cobalt powder and carbon black, pressed, and then subjected to pre-heating before liquid phase formation, pressure sintering, and segmented cooling in sequence. The pre-heating before liquid phase formation, pressure sintering, and segmented cooling include: first heating to 2.5-3.5℃ / min... The temperature is raised to 1180-1220℃ and held for 30-50 minutes, then increased to 1365-1380℃ at a rate of 4.5-5.5℃ / min and held for 20-28 minutes. Then, argon gas at 4-6 MPa is introduced at 1355-1365℃ and held for 15-25 minutes. After that, the temperature is lowered to 1260-1290℃ at a rate of 30-40℃ / min, then lowered to 1080-1120℃ at a rate of 8-12℃ / min, and finally cooled to room temperature in the furnace. Then, mirror polishing is performed to obtain the high wear-resistant cemented carbide mirror polished sheet.

2. The mirror polished plate of high wear resistant cemented carbide according to claim 1, characterized in that, The tungsten carbide powder has an average particle size of 350 nm, and the cobalt powder has an average particle size of 1.6 μm.

3. The high wear-resistant cemented carbide mirror-polished sheet metal according to claim 1, characterized in that, The surface activation is as follows: the tungsten carbide powder is added to anhydrous ethanol and deionized water, mechanically stirred at 8-15°C for 12-20 min, then a 30% hydrogen peroxide solution is added dropwise, and stirring is continued for 10-15 min. Subsequently, it is washed with anhydrous ethanol and vacuum dried to obtain surface-activated tungsten carbide powder.

4. The high wear-resistant cemented carbide mirror-polished sheet material according to claim 1, characterized in that, The vanadium-containing solution is added to the surface-activated tungsten carbide powder by atomization spraying, and the chromium source solution is sprayed into the resulting powder in three stages to form a layered precursor in which the vanadium-containing component is located in the inner layer and the chromium-containing component is located in the outer layer relative to the surface of the tungsten carbide particles before heat treatment.

5. The high wear-resistant cemented carbide mirror-polished sheet metal according to claim 1, characterized in that, The heat treatment is carried out in an argon-hydrogen mixed atmosphere and includes: heating to 430-470°C at 2°C / min and holding for 50-75 min, then heating to 860-900°C at 3°C / min and holding for 30-50 min, followed by furnace cooling.

6. The high wear-resistant cemented carbide mirror-polished sheet metal according to claim 5, characterized in that, The volume fraction of hydrogen in the argon-hydrogen mixture is 5%, and the mirror-polished surface is formed by sequential double-sided fine grinding with 15μm and 6μm diamond grinding discs, followed by sequential polishing with 3μm, 1μm and 0.25μm polycrystalline diamond suspensions.

7. A method for preparing a high wear-resistant cemented carbide mirror-polished sheet according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Surface-activate tungsten carbide powder to obtain surface-activated tungsten carbide powder; (2) Prepare a vanadium-containing solution by mixing ammonium metavanadate and oxalic acid dihydrate, and spray the vanadium-containing solution onto the surface-activated tungsten carbide powder and dry it; (3) Chromium nitrate nonahydrate is prepared into a chromium source solution, and the chromium source solution is sprayed onto the powder obtained in step (2), dried and then heat-treated to obtain composite tungsten carbide powder; (4) The composite tungsten carbide powder is mixed with cobalt powder and carbon black and wet-milled, dried, ground and sieved to obtain pressed particles; (5) Press the pressed particles into a slab; (6) The slab is preheated, pressurized and sintered before liquid phase formation, and then cooled in stages: first, the temperature is raised to 1180-1220℃ at 2.5-3.5℃ / min and held for 30-50min, then the temperature is raised to 1365-1380℃ at 4.5-5.5℃ / min and held for 20-28min, then 4-6MPa argon gas is introduced at 1355-1365℃ and held for 15-25min, then the temperature is lowered to 1260-1290℃ at 30-40℃ / min, then the temperature is lowered to 1080-1120℃ at 8-12℃ / min, and finally cooled to room temperature with the furnace to obtain the sintered slab; (7) The sintered plate is subjected to double-sided fine grinding and mirror polishing to obtain a high wear-resistant hard alloy mirror polished plate.

8. The method for preparing high wear-resistant cemented carbide mirror-polished sheet metal according to claim 7, characterized in that, In step (5), the pressed particles obtained in step (4) are loaded into a rectangular mold and unidirectionally pressed at 70-90MPa, and then cold isostatically pressed at 200-240MPa for 2.5-3.5min to obtain a slab.