WO2018099491A1 - 一种可调控板状wc晶粒排列状态的硬质合金的制备方法 - Google Patents

一种可调控板状wc晶粒排列状态的硬质合金的制备方法 Download PDF

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WO2018099491A1
WO2018099491A1 PCT/CN2017/117674 CN2017117674W WO2018099491A1 WO 2018099491 A1 WO2018099491 A1 WO 2018099491A1 CN 2017117674 W CN2017117674 W CN 2017117674W WO 2018099491 A1 WO2018099491 A1 WO 2018099491A1
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powder
plate
cemented carbide
grains
raw material
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French (fr)
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朱敏
王为
鲁忠臣
曾美琴
鲍贤勇
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华南理工大学
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
    • C22C29/02—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides
    • C22C29/06—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds
    • C22C29/08—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds based on tungsten carbide
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/05—Mixtures of metal powder with non-metallic powder
    • C22C1/051—Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor
    • C22C1/053—Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor with in situ formation of hard compounds
    • C22C1/055—Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor with in situ formation of hard compounds using carbon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
    • C22C29/02—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides
    • C22C29/06—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds
    • C22C29/067—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds comprising a particular metallic binder
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • B22F2998/10—Processes characterised by the sequence of their steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/12—Both compacting and sintering
    • B22F3/16—Both compacting and sintering in successive or repeated steps

Definitions

  • the invention relates to the preparation of a WC-Co cemented carbide, in particular to a method for preparing a cemented carbide which can regulate the arrangement state of the plate-like WC grains.
  • WC-Co cemented carbide As a hard material with high hardness and excellent wear resistance, WC-Co cemented carbide is widely used in the fields of machining and mining, and is known as “industrial teeth”.
  • traditional WC-Co cemented carbide as a cermet material, hardness and strength, that is, wear resistance and toughness (crack resistance) are two contradictory characteristics, which tend to sacrifice the toughness of the material when the hardness is increased, and vice versa.
  • many measures such as preparation of nano/ultrafine crystal WC, twin crystal structure WC, Co gradient functional cemented carbide, etc., which have both hardness, strength and toughness, have been well developed.
  • the WC crystal has a close-packed hexagonal structure.
  • the hardness of the (0001) crystal plane is higher than that of other crystal planes.
  • the WC grains in the conventional WC-Co cemented carbide are mostly triangular or polygonal prismatic bodies. If the (0001) plane of the triangular or polygonal prismatic body is preferentially grown, it can be transformed into a plate-shaped WC grain. And as the proportion of WC grains in the proportion of the (0001) plane increases, the overall hardness and toughness of the alloy are improved. Therefore, cemented carbide containing plate-like WC grains has better comprehensive mechanical properties than traditional cemented carbides, and has its unique advantages in practical applications. It is a new development direction in the field of cemented carbides.
  • the raw materials used for preparing the plate-shaped WC are generally the following three types: elemental W powder, WC powder, W x Co y C powder, and the like.
  • elemental W powder WC powder
  • W x Co y C powder W x Co y C powder
  • a common feature of these methods is that in the early stage of preparation of the plate-shaped WC process, it is preferred to prepare precursors (specially treated W, WC, W x Co y C, etc.) which can form a plate-like morphology WC during post-sintering.
  • the preparation method of a cemented carbide containing (bulk) plate-shaped tungsten carbide grains is disclosed in Chinese Patent Nos. CN101117673A and CN101376931A.
  • high-energy ball milling is used to ball-mill WC seed crystals and Co ball milling to prepare a mixture, followed by hot pressing sintering to obtain a mixed crystal structure composed of plate-like WC and conventional WC grains.
  • the plate-like side length is usually 3 to 8 ⁇ m, the size of the plate-shaped WC crystal grains is large, which is disadvantageous for the strengthening of the cemented carbide.
  • the plate-like WC has a preferred orientation characteristic of the (0001) plane perpendicular to the direction of the pressing force, resulting in anisotropy of the mechanical properties of the alloy.
  • Chinese patent CN1068067C publishes "hard alloy containing platelet tungsten carbide and its preparation method", which adopts a two-step process, that is, firstly forms a platelet WC containing Co 3 W 3 C, Co 6 W 6 C and the like. A powder, which is then combined with a carbon source compound to prepare a cemented carbide containing platelet WC.
  • this method has the disadvantage of poor process stability.
  • the process flow is cumbersome, the production cycle is long, the energy consumption is high, and the alignment orientation of the plate-shaped WC in the alloy block is not well regulated.
  • the relationship between the arrangement state of the plate-shaped WC grains and the mechanical properties of the cemented carbide is often manifested in the following two cases: (1) When the plate-like WC is disorderly arranged in the alloy, although the mechanical properties of the alloy have good uniformity.
  • an object of the present invention is to provide a method for preparing a cemented carbide which can regulate the arrangement state of the plate-shaped WC grains, and optimize the WC-Co cemented carbide of the plate-shaped WC grain.
  • the mechanical properties make the cemented carbide have excellent comprehensive mechanical properties, and the process is simple and the energy consumption is low.
  • a method for preparing a cemented carbide capable of regulating the arrangement state of plate-like WC grains comprising the following steps:
  • the fine particle W raw material has a particle size of 0.3 ⁇ m to 1 ⁇ m; the coarse particle W raw material has a particle size of 5 ⁇ m to 25 ⁇ m;
  • the weight ratio of the fine particle W raw material and the coarse particle W raw material is 1:4 to 4:1;
  • step (1) adding the graphite powder, Co powder and W powder of step (1), and adding the extra amount of carbon actually required, and placing it in a planetary ball mill for planetary ball milling to obtain W-C-Co powder;
  • the W-C-Co powder green body is carbonized and sintered at 1350 to 1550 °C.
  • the graphite powder of the step (1) has a particle size of from 20 ⁇ m to 80 ⁇ m.
  • the particle size of the Co powder in the step (1) is from 0.5 ⁇ m to 5 ⁇ m.
  • step (2) The specific parameters of the planetary ball mill of step (2) are:
  • the ball-to-batch ratio is 1:3 to 1:5, and the ball milling time is 5 to 10 hours.
  • the specific parameters of the plasma-assisted ball milling in the step (3) are: a ball-to-batch ratio of 30:1 to 60:1, a ball milling time of 3 to 6 hours, and a discharge current of 1 to 3 A.
  • the WC-Co composite powder according to the step (3) is composed of a small-scale sheet-like W sheet and a large-scale sheet-like W sheet, and the small-scale sheet-like W sheet has a length of 200 nm to 1.5 ⁇ m and a thickness of 40 nm to 200 nm; the large-scale sheet-like W sheet has a length of 3 ⁇ m to 15 ⁇ m and a thickness of 60 nm to 300 nm.
  • the carbonization sintering is vacuum sintering or low pressure sintering.
  • the present invention has the following advantages and benefits:
  • the invention adopts a two-step method of planetary low energy pre-ball milling and plasma-assisted ball milling to prepare alloy powder, and the planetary low-energy pre-ball milling is advantageous for WC- which has uniform distribution of powder components and low strength combination between particles.
  • Co powder to avoid the segregation of the powder in the subsequent plasma-assisted ball milling; in the plasma-assisted ball milling process, the W can be flattened in a shorter time (3-6 h) to obtain the WC- of the laminar W-sheet.
  • Co composite powder to avoid the segregation of the powder in the subsequent plasma-assisted ball milling; in the plasma-assisted ball milling process, the W can be flattened in a shorter time (3-6 h) to obtain the WC- of the laminar W-sheet.
  • the amount of the small-sized sheet-like W sheet and the large-scale sheet-like W sheet in the ball-milled WC-Co powder can be adjusted by adjusting the ratio of the weight of the small particle W raw material to the large particle W raw material.
  • the control of the ratio in turn, achieves the regulation of the orientation of the plate-like WC in the prepared cemented carbide in the cemented carbide, and optimizes the comprehensive mechanical properties of the alloy.
  • the WC-Co powder obtained after plasma-assisted ball milling for 3-6 hours can be directly carbonized and sintered in a high temperature environment to obtain a high content of plate-like WC, plate shape.
  • the amount ratio of WC grains in the alloy is greater than 65%.
  • the preparation process of the invention is short and easy to operate, and the main steps are "pre-ball milling, plasma-assisted ball milling, powder compression molding, in-situ high-temperature carbonization sintering" powdering to overcome the conventional method for preparing high content plate-shaped WC hard
  • the production cycle of the alloy is long, the preparation process is cumbersome, and the energy consumption is high.
  • Figure 1 is a schematic diagram of the definition and test of different sections of cemented carbide.
  • Example 2 is a topographical view of the F powder after ball milling of Example 1.
  • Example 3 is a three-dimensional topography of the plate-like WC in the sample F of Example 1.
  • Fig. 5 is an XRD chart of the sample F of Example 1 in a cross section.
  • Fig. 6 is a SEM image of the microstructure of the sample F of Example 1 in a longitudinal section.
  • Fig. 7 is an XRD chart of the sample F of Example 1 in a longitudinal section.
  • Fig. 8 is a topographical view of the P powder after ball milling of Example 1.
  • Fig. 9 is a three-dimensional topography of the plate-like WC in the sample P of Example 1.
  • Figure 10 is an SEM image of the microstructure of the sample P of Example 1 in cross section.
  • Figure 11 is an XRD chart of the sample P of Example 1 in cross section.
  • Fig. 12 is an SEM image showing the microstructure of the sample P of Example 1 in a longitudinal section.
  • Fig. 13 is an XRD chart of the sample P of Example 1 in a longitudinal section.
  • Figure 14 is a SEM image of the microstructure of the sample F1P1 of Example 1 in cross section.
  • Figure 15 is an XRD pattern of the sample F1P1 of Example 1 in cross section.
  • Fig. 16 is a SEM image showing the microstructure of the sample F1P1 of Example 1 in the longitudinal section.
  • Fig. 17 is an XRD chart of the sample F1P1 of Example 1 in a longitudinal section.
  • Figure 18 is an XRD pattern of a sample T3G2 cemented carbide block of Example 6 in cross section.
  • Figure 19 is an XRD pattern of the sample T3G2 cemented carbide block of Example 6 in a longitudinal section.
  • Figure 20 is an XRD pattern of the sample T2G3 cemented carbide block of Example 7 in cross section.
  • Figure 21 is an XRD pattern of the sample T2G3 cemented carbide block of Example 7 in a longitudinal section.
  • Figure 22 is an XRD chart of a cross section of a sample T1G4 cemented carbide block in Example 8.
  • Figure 23 is an XRD chart of the longitudinal section of the sample T1G4 cemented carbide block in Example 8.
  • the method for preparing the WC-Co cemented carbide in the state in which the plate-like WC grains are arranged in the embodiment includes the following steps:
  • a W raw material having a particle size of 0.5 ⁇ m and a W raw material having a particle size of 12 ⁇ m were selected as a source of W powder.
  • the composition of the W powder is composed of a W material having a particle size of 0.5 ⁇ m and a W material having a particle size of 12 ⁇ m in a weight ratio of 1:1, and is weighed with a graphite powder having a size of 30 ⁇ m and 0.5.
  • the ⁇ m Co powder has an additional carbon content of 5.8% of the theoretical alloy composition carbon content.
  • the WC-Co composite powder containing the lamellar W-sheets combined in two dimensions and sizes obtained in the step (3) is loaded into the mold, and is pressed by a one-way axial compression molding, and the pressing pressure is 220 MPa, and the pressure holding time is After 3 min, the mold was released to obtain a powder green body.
  • the green body is sintered by a low pressure sintering process.
  • the low-pressure sintering process is as follows: after vacuuming to 1 Pa, the temperature is raised to 1390 ° C at a heating rate of 10 K/min. After the temperature reaches the highest temperature, it is filled with 4 MPa Ar gas, kept for 60 min, and then cooled to room temperature at a cooling rate of 20 K/min.
  • a WC-Co cemented carbide having a plate-like WC grain was obtained, which was designated as sample F1P1.
  • W raw material with particle size of 0.5 ⁇ m and W raw material with particle size of 12 ⁇ m were pre-blanched and plasma ball-milled with graphite powder and Co powder, respectively, to obtain a single-scale WC-Co powder containing lamellar W-wafer, which was pressed.
  • the samples obtained after sintering were designated as sample F and sample P, respectively, and used as a comparative sample.
  • Fig. 8 it can be seen that in the WC-Co composite powder obtained by using 12 ⁇ m W of the raw material as the W powder, most of the sheet layer W has a length of 3.0 to 10.0 ⁇ m and a thickness of 150 to 310 nm.
  • Figure 9 shows that the WC in the P sample also has a distinct plate-like characteristic. The average grain size of the plate-like WC is 1.21 ⁇ m, and the WC content of the plate is 72.2%.
  • Figure 10 shows that the WC shape in the cross section is a triangle.
  • Figure 12 shows that the shape of the WC is mostly strip shape, and the different appearance of the WC in the cross section and the longitudinal section indicates that the plate-like WC has a highly directional arrangement.
  • the peak shape of XRD in Fig. 11 and Fig. 13 and the cross section and the longitudinal section are shown in Table 1.
  • the ratios are 2.85 and 0.27, indicating that the plate-like WC is in a highly oriented state.
  • the morphology of the different alloy sections in Figures 14-17 and the orientation of the plate-like WC of the F1P1 specimen are given in Table 1: cross-section and longitudinal section The ratios are 1.31 and 0.35, respectively.
  • the content of the plate-like WC in the alloy was 70.4%.
  • the steps of this example are basically the same as those of the embodiment 1, except that the W raw material having a particle size of 0.5 ⁇ m and the W raw material having a particle size of 12 ⁇ m in the step (1) are 4:1 by weight, and the additional carbon is added.
  • the WC-8Co cemented carbide of the plate-shaped WC grain prepared by the low-pressure sintering process is recorded as the sample F4P1, and the degree of orientation of the plate-like WC in the alloy is listed in Table 1, and the alloy is different.
  • the mechanical properties of the cross section are shown in Table 2.
  • the orientation of the plate FC of the sample F4P1 is: cross section and longitudinal section The ratios were 0.86 and 0.37, respectively.
  • the content of the plate-like WC in the alloy was 69.3%.
  • the steps of this example are basically the same as those of the first embodiment, except that the W raw material having a particle size of 0.5 ⁇ m and the W raw material having a particle size of 12 ⁇ m in the step (1) are 3:2 by weight, and the additional carbon amount is added.
  • the W raw material having a particle size of 0.5 ⁇ m and the W raw material having a particle size of 12 ⁇ m in the step (1) are 3:2 by weight, and the additional carbon amount is added.
  • the WC-8Co cemented carbide of the plate-shaped WC grain prepared by the low-pressure sintering process, recorded as the sample F3P2 the degree of orientation of the plate-like WC in the alloy is listed in Table 1, alloy The mechanical properties of materials with different cross sections are shown in Table 2.
  • the orientation of the plate FC of the sample F3P2 is: cross section and longitudinal section The ratios are 1.06 and 0.36, respectively.
  • the content of the plate-like WC in the alloy was 70.2%.
  • the steps of this example are basically the same as those of the embodiment 1, except that the W raw material having a particle size of 0.5 ⁇ m and the W raw material having a particle size of 12 ⁇ m in the step (1) are 2:3 by weight, and the additional carbon is added.
  • the W raw material having a particle size of 0.5 ⁇ m and the W raw material having a particle size of 12 ⁇ m in the step (1) are 2:3 by weight, and the additional carbon is added.
  • the WC-8Co cemented carbide of the plate-shaped WC grain prepared by the low-pressure sintering process, recorded as the sample F2P3 recorded as the sample F2P3
  • the degree of orientation of the plate-like WC in the alloy is listed in Table 1, alloy
  • the mechanical properties of materials with different cross sections are shown in Table 2.
  • the orientation of the F2P3 plate-like WC is: cross section and longitudinal section The ratios were 1.77 and 0.33, respectively.
  • the content of the plate-like WC in the alloy was 70.7%.
  • the steps of this example are basically the same as those of the first embodiment, except that the W raw material having a particle size of 0.5 ⁇ m and the W raw material having a particle size of 12 ⁇ m in the step (1) are 1:4 by weight, and the additional carbon is added.
  • the WC-8Co cemented carbide of the plate-shaped WC grain prepared by the low-pressure sintering process, recorded as the sample F1P4 the degree of orientation of the plate-like WC in the alloy is listed in Table 1, alloy The mechanical properties of materials with different cross sections are shown in Table 2.
  • the orientation of the plate-shaped WC of the sample F1P4 is: cross section and longitudinal section The ratios were 1.96 and 0.31, respectively.
  • the content of the plate-like WC in the alloy was 71.5%.
  • a W raw material having a particle size of 0.3 ⁇ m and a W raw material having a particle size of 5 ⁇ m were selected as a source of W powder.
  • the composition of the W powder is composed of a W material having a particle size of 0.3 ⁇ m and a W material having a particle size of 5 ⁇ m in a weight ratio of 3:2, and is weighed with a graphite powder having a size of 20 ⁇ m and 5 ⁇ m.
  • the Co powder has an additional carbon content of 8.0% of the carbon content of the alloy composition.
  • the size-size sheet-like W sheet has a length of 0.8 to 4.5 ⁇ m and a thickness of about 120 to 240 nm.
  • the WC-Co composite powder containing the lamellar W-sheets combined in two dimensions and sizes obtained in the step (3) is loaded into the mold, and is pressed by a one-way axial compression molding, and the pressing pressure is 150 MPa, and the pressure holding time is After 4 min, the mold was subsequently released to obtain a powder green body.
  • the green body is sintered by a low pressure sintering process.
  • the low-pressure sintering process is as follows: after vacuuming to 1 Pa, the temperature is raised to 1430 ° C at a heating rate of 10 K/min. After the temperature reaches the highest temperature, it is filled with 5 MPa Ar gas, kept for 45 minutes, and then cooled to room temperature at a cooling rate of 20 K/min.
  • WC-Co cemented carbide with plate-like WC grains recorded as sample T3G2, cross-section and longitudinal section The ratios were 1.04 and 0.37, respectively.
  • the content of the plate-like WC in the alloy was 71.7%.
  • the XRD patterns of the T3G2 samples on different cross sections are shown in Figs. 18 to 19, and the degree of orientation of the plate-like WC in the alloy is shown in Table 3.
  • the mechanical properties of the materials are shown in Table 4.
  • the steps of this example are basically the same as those of the embodiment 6, except that the W raw material having a particle size of 0.3 ⁇ m and the W raw material having a particle size of 5 ⁇ m in the step (1) are 2:3 by weight, and the additional carbon amount is added.
  • the WC-6Co cemented carbide of the plate-shaped WC grain prepared by the low-pressure sintering process recorded as the sample T2G3, its cross section and longitudinal section The ratios are 1.37 and 0.32, respectively.
  • the content of the plate-like WC in the alloy was 75.0%.
  • the XRD patterns of the T2G3 samples on different sections are shown in Figures 20-21.
  • the degree of orientation of the plate-like WC in the alloy is shown in Table 3.
  • the mechanical properties of the materials are shown in Table 4.
  • the steps of this example are basically the same as those of the embodiment 6, except that the W raw material having a particle size of 0.3 ⁇ m and the W raw material having a particle size of 5 ⁇ m in the step (1) are 1:4 by weight, and the additional carbon is added.
  • the WC-6Co cemented carbide of the plate-shaped WC grain prepared by the low-pressure sintering process recorded as the sample T1G4, its cross section and longitudinal section The ratios were 1.78 and 0.31, respectively.
  • the content of the plate-like WC in the alloy was 78.3%.
  • the XRD patterns of the T1G4 samples on different sections are shown in Figures 22 to 23.
  • the degree of orientation of the plate-like WC in the alloy is shown in Table 3.
  • the mechanical properties of the materials are shown in Table 4.
  • a W raw material having a particle size of 1.0 ⁇ m and a W raw material having a particle size of 25 ⁇ m were selected as a source of W powder.
  • the composition of the W powder is composed of a W material having a particle size of 1.0 ⁇ m and a W material having a particle size of 5 ⁇ m in a weight ratio of 4:1, and is weighed with a graphite powder of a size of 80 ⁇ m and 1.5.
  • the ⁇ m Co powder has an additional carbon content of 8.0% of the carbon content of the alloy composition.
  • the pre-ball-milled WC-Co powder was then placed in a plasma-assisted ball mill for 6 h plasma ball milling with a ball-to-batch ratio of 30:1, a ball-milling speed of 1200 r/min, and a discharge current of 2.0 A.
  • a WC-Co composite powder in which a small-scale sheet-like W sheet and a large-scale sheet-like W sheet are combined; the small-scale sheet-like W sheet has a length of 0.4 to 1.2 ⁇ m and a thickness of about 100 to 200 nm.
  • the large-scale sheet-like W sheet has a length of 3.0 to 11.0 um and a thickness of about 100 to 250 nm.
  • the WC-Co composite powder containing the lamellar W-sheets combined in two dimensions and sizes obtained in the step (3) is loaded into the mold, and is pressed by a one-way axial compression molding, and the pressing pressure is 150 MPa, and the pressure holding time is After 4 min, the mold was subsequently released to obtain a powder green body.
  • the green body is sintered by a low pressure sintering process.
  • the low-pressure sintering process is: after vacuuming to 1 Pa, the temperature is raised to 1500 ° C at a heating rate of 10 K/min. After the temperature reaches the highest temperature, it is filled with 4.5 MPa Ar gas, kept for 30 min, and then cooled to a cooling rate of 20 K/min.
  • WC-20Co cemented carbide with plate-like WC grains was obtained, which was recorded as sample X4Y1, its cross section and longitudinal section. The ratios were 0.96 and 0.33, respectively.
  • the content of the plate-like WC in the alloy was 75.5%.
  • the degree of orientation of the plate-like WC in the X4Y1 sample in the alloy is shown in Table 5, and the mechanical properties of the material are shown in Table 6.
  • the steps of this example are basically the same as those of the embodiment 9, except that the W raw material having a particle size of 1.0 ⁇ m and the W raw material having a particle size of 25 ⁇ m in the step (1) are 1:1 by weight, and the additional carbon amount is added.
  • the WC-20Co cemented carbide of the plate-shaped WC grain prepared by the low-pressure sintering process, recorded as sample X1Y1, its cross section and longitudinal section The ratios are 1.82 and 0.27, respectively.
  • the content of the plate-like WC in the alloy was 78.9%.
  • the degree of orientation of the plate-like WC in the X1Y1 sample in the alloy is shown in Table 5, and the mechanical properties of the material are shown in Table 6.
  • the steps of this example are basically the same as those of the embodiment 9, except that the W raw material having a particle size of 1.0 ⁇ m and the W raw material having a particle size of 25 ⁇ m in the step (1) are 1:4 by weight, and the additional carbon amount is added.
  • the WC-20Co cemented carbide of the plate-shaped WC grain prepared by the low-pressure sintering process recorded as the sample X1Y4, its cross section and longitudinal section The ratios were 2.84 and 0.21, respectively.
  • the content of the plate-like WC in the alloy was 82.4%.
  • the degree of orientation of the plate-like WC in the X1Y4 sample in the alloy is shown in Table 5, and the mechanical properties of the material are shown in Table 6.

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Abstract

一种可调控板状WC晶粒排列状态的硬质合金的制备方法，按合金的理论成分计，称取的W粉由两种颗粒大小明显不同的W原料以一定的重量比例所组成，并称取石墨粉及Co粉；通过调节行星式球磨的工艺参数先对W‑C‑Co粉末进行行星式球磨；然后再通过调控等离子体辅助球磨，获得由小尺寸片层状W薄片与大尺度片层状W薄片共同组成的W‑C‑Co复合粉末；随后将球磨粉末进行压制成型，经高温原位碳化烧结得到致密的板状WC晶粒硬质合金。由此实现烧结块体中板状WC排列取向程度的调控，进一步优化了板状WC晶粒WC‑Co硬质合金的力学性能，使硬质合金具有优良的综合力学性能。

Description

一种可调控板状WC晶粒排列状态的硬质合金的制备方法 技术领域
本发明涉及WC-Co硬质合金的制备，特别涉及一种可调控板状WC晶粒排列状态的硬质合金的制备方法。
背景技术
WC-Co硬质合金作为一种具有高硬度、优异的耐磨性的硬质材料，被广泛应用于在机加工业及采掘业等领域，被誉为“工业的牙齿”。然而，传统WC-Co硬质合金作为一种金属陶瓷材料，硬度和强度即耐磨性和韧性(抗裂性)是相互矛盾的两项特性，在提高硬度往往会牺牲材料的韧性，反之亦然，这就限制了硬质合金的进一步发展。因此发展同时兼顾高硬度、高强度、高韧性等力学性能的硬质合金成为硬质合金研究领域的重点。针对这一情况，诸多措施例如制备纳米/超细晶WC、双晶结构WC，Co梯度功能硬质合金等可兼顾硬度、强度及韧性的方法均取得了较好的发展。
WC晶体具有密排六方结构，作为一种六方晶系的各向异性晶体，其(0001)晶面上的硬度要高于其它晶面上的硬度。但传统WC-Co硬质合金中的WC晶粒多为三角或者多角棱柱状体，若三角或多角棱柱状体的发生(0001)面的择优长大，则可转变为板状WC晶粒，且随着(0001)面所占比例的WC晶粒所占比例的增加，合金整体硬度和韧性都会得到提高。因此，含板状WC晶粒的硬质合金要比传统硬质合金具有更好的综合力学性能，在实际应用中具有其独特的优势，是硬质合金领域中的一个新的发展方向。
目前，制备板状WC的所使用的原材料一般为以下3种：单质W粉末、WC粉末、W xCo yC粉末等。这些方法的共同特点是在于制备板状WC流程的前期阶段中，优先制备出具有后期烧结过程中可生成板状形态WC的前驱体(特殊处理的W、WC、W xCo yC等)。
研究报道称采用微米级W粉，经特殊处理后，促使W转变为板状体来制备含板状WC晶粒的硬质合金。但该类方法的缺点在于板状体W的含量低，需要提高烧结温度及延长烧结时间来获得板状WC，不仅板状WC的产量低，难以实现对板状WC的比例调控，制备周期长，工艺繁琐，能耗高。
中国专利CN101117673A及CN101376931A中公布了“含(大块)板状碳化钨晶粒的硬质合金的制备方法”。该方法中采用高能球磨对板状WC晶种及Co 进行球磨制备混合料，后续热压烧结得到了板状WC与常规WC晶粒组成的混晶结构。但由于板状边长通常在3～8μm，板状WC晶粒的尺寸较大，对硬质合金的强化不利。并且板状WC具有垂直于压制力方向的(0001)面的择优取向特征，导致了合金力学性能的各向异性。
中国专利CN1068067C公布了“含片晶碳化钨的硬质合金及其制备方法”，其采用两步法工艺，即先制备出含Co 3W 3C，Co 6W 6C等的片晶WC形成粉末，再将该粉末与碳源化合物来制备含片晶WC的硬质合金。但该方法的缺点是工艺稳定性差。
上述方法虽然较好的制备板状WC，明显的不足之处在于工艺流程较为繁琐，生产周期长，能耗高，而且对板状WC在合金块体中的排列取向没有进行较好的调控。而板状WC晶粒的排列状态与硬质合金力学性能的关系常表现为以下两种情况：(1)当板状WC混乱排列于合金中时，虽然合金的力学性能具有较好的均一性，但其力学性能相对于定向排列时较差；(2)当板状WC处于高度定向排列时，虽然合金在WC(0001)晶面较多的部位具有优异的性能，但由于WC的各向异性，其他部位的性能相对较差，实际工况应用中不利于合金力学性能的发挥。由此可见，寻求一种能耗低，生产周期短，既可高效制备高含量板状WC晶粒，且可对板状WC晶粒排列取向进行较好的调控，同时保证硬质合金具有较好的力学性能均匀性的板状WC硬质合金的制备方法变得至关重要。
发明内容
为了克服现有技术的上述缺点与不足，本发明的目的在于提供一种可调控板状WC晶粒排列状态的硬质合金的制备方法，优化了板状WC晶粒WC-Co硬质合金的力学性能，使硬质合金具有优良的综合力学性能，并且工艺简单，耗能低。
本发明的目的通过以下技术方案实现：
一种可调控板状WC晶粒排列状态的硬质合金的制备方法，包括以下步骤：
(1)按WC-XCo的成分称量石墨粉、Co粉与W粉；其中W粉包括细小颗粒的W原料和粗大颗粒的W原料，其中6≤X≤20；
所述细小颗粒的W原料的颗粒尺寸为0.3μm～1μm；所述粗大颗粒的W原料的颗粒尺寸为5μm～25μm；
所述细小颗粒的W原料和粗大颗粒的W原料的重量比为1:4～4:1；
(2)将步骤(1)的石墨粉、Co粉与W粉，并加入实际所需的额外碳量， 置于行星式球磨机中进行行星式球磨，得到W-C-Co粉末；
(3)将步骤(2)得到的W-C-Co粉末置于等离子体辅助高能球机中，进行等离子体辅助球磨，得到W-C-Co复合粉末；
(4)将步骤(3)得到的W-C-Co复合粉末进行单向轴压压制成型，得到W-C-Co粉末生坯；
(5)将W-C-Co粉末生坯于1350～1550℃中进行碳化烧结。
步骤(1)所述石墨粉的颗粒尺寸为20μm～80μm。
步骤(1)所述Co粉的颗粒尺寸为0.5μm～5μm。
步骤(2)所述行星式球磨的具体参数为：
球料比为1:3～1:5，球磨时间为5～10h。
步骤(3)所述等离子体辅助球磨的具体参数为：球料比为30:1～60:1，球磨时间为3～6h，放电电流为1～3A。
步骤(3)所述W-C-Co复合粉末，由小尺度片层状W薄片与大尺度片层状W薄片共同组成，所述小尺度片层状W薄片的长度为200nm～1.5μm，厚度为40nm-200nm；所述大尺度片层状W薄片的长度为3μm～15μm，厚度为60nm～300nm。
所述碳化烧结为真空烧结或低压烧结。
与现有技术相比，本发明具有以下优点和有益效果：
(1))本发明采用了行星式低能预球磨及等离子体辅助球磨的两步法来制备合金粉末，行星式低能量预球磨有利于粉末成分分布均匀且颗粒之间达到低强度结合的W-C-Co粉末，以避免后续等离子体辅助球磨中粉末的偏聚；采用等离子体辅助球磨过程中可在较短时间内(3～6h)对W进行扁平化处理以获得片层状W薄片的W-C-Co复合粉末。
(2)本发明通过调配小颗粒W原料与大颗粒W原料的重量之比，可对球磨后的W-C-Co粉末中的小尺度片层状W薄片与大尺度片层状W薄片的进行数量比例的控制，进而实现所制备的硬质合金中板状WC在硬质合金中排列取向的调控，优化合金的综合力学性能。
(3)相比于其它制备板状WC的方法，等离子体辅助球磨的时间为3～6h后得到的W-C-Co粉末，在高温环境中可直接碳化烧结获得高含量的板状WC，板状WC晶粒在合金中的数量比大于65％。
(4)本发明的制备工艺流程短，操作简便，主要步骤为“预球磨、等离子体辅助球磨、粉末压制成型、原位高温碳化烧结”制粉克服了传统技术中制备高 含量板状WC硬质合金中生产周期长，制备工艺繁琐，能耗高的缺点。
附图说明
图1为硬质合金不同截面的定义及测试示意图。
图2为实施例1的球磨后F粉末的形貌图。
图3为实施例1的试样F中板状WC的三维形貌。
图4为实施例1的试样F在横截面上的组织形貌SEM图。
图5为实施例1的试样F在横截面上的XRD图。
图6为实施例1的试样F在纵截面上的组织形貌SEM图。
图7为实施例1的试样F在纵截面上的XRD图。
图8为实施例1的球磨后P粉末的形貌图。
图9为实施例1的试样P中板状WC的三维形貌。
图10为实施例1的试样P在横截面上的组织形貌SEM图。
图11为实施例1的试样P在横截面上的XRD图。
图12为实施例1的试样P在纵截面上的组织形貌SEM图。
图13为实施例1的试样P在纵截面上的XRD图。
图14为实施例1的试样F1P1在横截面上的组织形貌SEM图。
图15为实施例1的试样F1P1在横截面上的XRD图。
图16为实施例1的试样F1P1在纵截面上的组织形貌SEM图。
图17为实施例1的试样F1P1在纵截面上的XRD图。
图18为实施例6的试样T3G2硬质合金块体在横截面上的XRD图。
图19为实施例6的试样T3G2硬质合金块体在纵截面上的XRD图。
图20为实施例7的试样T2G3硬质合金块体在横截面上的XRD图。
图21为实施例7的试样T2G3硬质合金块体在纵截面上的XRD图。
图22为实施例8中的试样T1G4硬质合金块体在横截面上的XRD图。
图23为实施例8中的试样T1G4硬质合金块体在纵截面上的XRD图。
具体实施方式
下面结合实施例，对本发明作进一步地详细说明，但本发明的实施方式不限于此。
实施例1
如图1所示，本实施例的可调控板状WC晶粒排列状态的WC‐Co硬质合金的制备方法包括以下步骤：
(1)以WC-8wt.％Co为最终成分，选取颗粒大小为0.5μm的W原料与颗粒大小为12μm的W原料作为W粉的来源。按合金的理论成分计，W粉的组成由颗粒大小为0.5μm的W原料与颗粒大小为12μm的W原料以重量比例为1:1所共同组成，并称取与30μm大小的石墨粉及0.5μm的Co粉，额外补碳量为理论合金成分碳含量的5.8％。
(2)将上述W粉，石墨粉，Co粉置于行星式球磨机中进行5h低能量预球磨，球磨转速为200r/min，球料比为1:5，以实现粉末的均匀化分布及粉末颗粒之间的低强度结合，得到预球磨的W-C-Co粉末；
(3)随后将预球磨后的W-C-Co粉末置于等离子体辅助球磨机种进行3h的等离子体辅助球磨，球料比为50:1，球磨转速为960r/min，放电电流为1.5A，得到具有小尺度片层状W薄片与大尺度片层状W薄片相组合的W-C-Co复合粉末；
(4)将步骤(3)中得到的含两种尺度大小相结合的片层状W薄片的W-C-Co复合粉末装入模具，采用单向轴压压制成型，压制压强为220Mpa，保压时间3min，随后脱模，得到粉末生坯。
(5)采用低压烧结工艺对生坯进行烧结。低压烧结工艺为：抽真空至1Pa后以升温速率为10K/min升温至1390℃，待温度达到最高温后，同时充入4MPa Ar气，保温60min，随后以20K/min的降温速度冷却至室温，得到板状WC晶粒的WC-Co硬质合金，记为试样F1P1。
将颗粒大小为0.5μm的W原料与颗粒大小为12μm的W原料，分别与石墨粉、Co粉进行预球磨及等离子球磨，得到单一尺度的含片层状W薄片的W-C-Co粉末，经压制烧结后得到的试样分别记为试样F及试样P，并作为对比样。
利用扫描电子显微镜及XRD对试样F及试样P的粉末形态、碳化烧结后的板状WC的三维形貌，以及在不同块体截面上的形貌图及物相组成进行了观察和表征，分别见于图2～图7及图8～图13；试样F1P1的不同截面的形貌图及XRD见于图14～图17。板状WC的排列取向程度的表征主要体现在XRD图中WC(0001)晶面的峰强与
Figure PCTCN2017117674-appb-000001
晶面的峰强的比值，记为
Figure PCTCN2017117674-appb-000002
列于表1。在合金不同截面上进行了力学性能测试，所得测试值列于表2。
图2中可以看出由0.5μm W原料作为W粉得到的W-C-Co复合粉末中，W具有明显的片层结构，片层的长度处于0.3～1.0um，厚度约为60～180nm。图3显示，F试样中的WC具有明显的板状特征，板状WC的平均晶粒大小为552nm，板状WC的含量为68.5％，图4及图6显示板状WC在横截面及纵截面上的形貌相似，说明板状WC排列较为混乱，这与图5及图7的得到的XRD峰型相吻 合；表1中给出了横截面及纵截面上的
Figure PCTCN2017117674-appb-000003
比值为0.71和0.43，进一步说明板状WC排列混乱。从表2可知，F试样具有较好的力学均匀性：横截面上的硬度约为92.3HRA,TRS＝2926MPa，断裂韧性为18.75MPa*m 1/2；纵截面上的硬度为92.2HRA，TRS＝2865MPa，断裂韧性为18.67MPa*m 1/2。
图8中可以看出由12μm W原料作为W粉得到的W-C-Co复合粉末中，大多数片层W的长度处于3.0～10.0μm，厚度处于150～310nm。图9显示，P试样中的WC同样具有明显的板状特征，板状WC的平均晶粒大小为1.21μm，板状WC的含量为72.2％，图10显示横截面上的WC形状为三角形或截角三角形，而图12显示WC的形态多为条形，WC在横截面及纵截面上的呈现不同形貌说明板状WC具有高度定向排列的特点。图11和图13中的XRD的峰型及表1显示横截面及纵截面上
Figure PCTCN2017117674-appb-000004
比值为2.85及0.27，说明板状WC处于高度定向排列的状态。如表2可知，P试样中的板状WC高度定向排列导致不同截面上的合金力学性能有所差异：横截面上的硬度约为92.6HRA,TRS＝3389MPa，断裂韧性为19.52MPa*m 1/2；纵截面上的硬度为92.1HRA，TRS＝2757MPa，断裂韧性为18.53MPa*m 1/2。
对于F1P1试样而言，图14～17中的不同合金截面上的形貌及表1中给出了F1P1试样的板状WC的定向程度为：横截面及纵截面的
Figure PCTCN2017117674-appb-000005
比值分别为1.31和0.35。横截面及纵截面上的力学性能虽有所差异，但整体力学性能优良：横截面上的硬度约为92.3HRA,TRS＝3720MPa，断裂韧性为21.56MPa*m 1/2；纵截面上的硬度为92.2HRA，TRS＝3531MPa，断裂韧性为21.83MPa*m 1/2。合金中板状WC的含量为70.4％。
实施例2
本实施例步骤与实施例1基本相同，所不同之处在于步骤(1)中的颗粒大小为0.5μm的W原料与颗粒大小为12μm的W原料以重量比例为4:1，额外补碳量为理论合金成分碳含量的7.2％，低压烧结工艺制备的板状WC晶粒的WC-8Co硬质合金记为试样F4P1，板状WC在合金中的排列取向程度列于表1，合金不同截面的材料力学性能见于表2。试样F4P1板状WC的定向程度为：横截面及纵截面的
Figure PCTCN2017117674-appb-000006
比值分别为0.86和0.37。横截面上的硬度约为92.2HRA,TRS＝3191MPa，断裂韧性为19.43MPa*m 1/2；纵截面上的硬度为92.2HRA，TRS＝3224MPa，断裂韧性为19.87MPa*m 1/2。合金中板状WC的含量为69.3％。
实施例3
本实施例步骤与实施例1基本相同，所不同之处在于步骤(1)中的颗粒大 小为0.5μm的W原料与颗粒大小为12μm的W原料以重量比例为3:2，额外补碳量为理论合金成分碳含量的6.2％，低压烧结工艺制备的板状WC晶粒的WC-8Co硬质合金，记为试样F3P2，板状WC在合金中的排列取向程度列于表1，合金不同截面的材料力学性能见于表2。试样F3P2板状WC的定向程度为：横截面及纵截面的
Figure PCTCN2017117674-appb-000007
比值分别为1.06和0.36。横截面上的硬度约为92.3HRA,TRS＝3428MPa，断裂韧性为20.12MPa*m 1/2；纵截面上的硬度为92.1HRA，TRS＝3398MPa，断裂韧性为20.04MPa*m 1/2。合金中板状WC的含量为70.2％。
实施例4
本实施例步骤与实施例1基本相同，所不同之处在于步骤(1)中的颗粒大小为0.5μm的W原料与颗粒大小为12μm的W原料以重量比例为2:3，额外补碳量为理论合金成分碳含量的5.4％，低压烧结工艺制备的板状WC晶粒的WC-8Co硬质合金，记为试样F2P3，板状WC在合金中的排列取向程度列于表1，合金不同截面的材料力学性能见于表2。试样F2P3板状WC的定向程度为：横截面及纵截面的
Figure PCTCN2017117674-appb-000008
比值分别为1.77和0.33。横截面上的硬度约为92.4HRA,TRS＝3826MPa，断裂韧性为21.60MPa*m 1/2；纵截面上的硬度为92.2HRA，TRS＝3117MPa，断裂韧性为20.48MPa*m 1/2。合金中板状WC的含量为70.7％。
实施例5
本实施例步骤与实施例1基本相同，所不同之处在于步骤(1)中的颗粒大小为0.5μm的W原料与颗粒大小为12μm的W原料以重量比例为1:4，额外补碳量为理论合金成分碳含量的4.5％，低压烧结工艺制备的板状WC晶粒的WC-8Co硬质合金，记为试样F1P4，板状WC在合金中的排列取向程度列于表1，合金不同截面的材料力学性能见于表2。试样F1P4板状WC的定向程度为：横截面及纵截面的
Figure PCTCN2017117674-appb-000009
比值分别为1.96和0.31。横截面上的硬度约为92.6HRA,TRS＝3562MPa，断裂韧性为20.13MPa*m 1/2；纵截面上的硬度为92.1HRA，TRS＝2964MPa，断裂韧性为19.62MPa*m 1/2。合金中板状WC的含量为71.5％。
综合实施例1到实施例5的结果(见于表1及表2)可知，通过调控含细小尺度的片层状W薄片的W-C-Co复合粉末与含粗大尺度的片层状W薄片的W-C-Co复合粉末的重量之比，可实现所制备的硬质合金中板状WC在硬质合金中排列取向的控制，进而优化合金整体的力学性能。
表1.含板状WC晶粒WC-8Co硬质合金中板状WC的排列取向程度
Figure PCTCN2017117674-appb-000010
表2.含板状WC晶粒WC-8Co硬质合金的物理及力学性能
Figure PCTCN2017117674-appb-000011
Figure PCTCN2017117674-appb-000012
实施例6
(1)以WC-6wt.％Co为最终成分，选取颗粒大小为0.3μm的W原料与颗粒大小为5μm的W原料作为W粉的来源。按合金的理论成分计，W粉的组成由颗粒大小为0.3μm的W原料与颗粒大小为5μm的W原料以重量比例为3:2所共同组成，并称取与20μm大小的石墨粉及5μm的Co粉，额外补碳量为合金成分碳含量的8.0％。
(2)将上述W粉，石墨粉，Co粉置于行星式球磨机中进行8h低能量预球磨，球磨转速为150r/min，球料比为1:4，以实现粉末的均匀化分布及粉末颗粒之间的低强度结合，得到预球磨的W-C-Co粉末；
(3)随后将预球磨后的W-C-Co粉末置于等离子体辅助球磨机种进行4.5h的等离子体球磨，球料比为40:1，球磨转速为1100r/min，放电电流为2.5A，得到具有小尺度片层状W薄片与大尺度片层状W薄片相组合的W-C-Co复合粉末；小尺度片层状W薄片的长度处于0.3～0.6μm，厚度约为50～120nm。，大小尺度片层状W薄片的长度处于0.8～4.5μm，厚度约为120～240nm。
(4)将步骤(3)中得到的含两种尺度大小相结合的片层状W薄片的W-C-Co复合粉末装入模具，采用单向轴压压制成型，压制压强为150Mpa，保压时间4min，随后脱模，得到粉末生坯。
(5)采用低压烧结工艺对生坯进行烧结。低压烧结工艺为：抽真空至1Pa后以升温速率为10K/min升温至1430℃，待温度达到最高温后，同时充入5MPa Ar气，保温45min，随后以20K/min的降温速度冷却至室温，得到板状WC晶粒的WC-Co硬质合金，记为试样T3G2，其横截面及纵截面的
Figure PCTCN2017117674-appb-000013
比值分别为1.04和0.37。横截面上的硬度约为92.4HRA，TRS＝3282MPa，断裂韧性为18.32MPa*m 1/2；纵截面上的硬度为92.3HRA，TRS＝3218MPa，断裂韧性为18.69MPa*m 1/2。合金中板状WC的含量为71.7％。该T3G2试样在不同截面上的XRD谱图见于图18～19，板状WC在合金中的排列取向程度列于表3。材料力学性能见于表4。
实施例7
本实施例步骤与实施例6基本相同，所不同之处在于步骤(1)中的颗粒大小为0.3μm的W原料与颗粒大小为5μm的W原料以重量比例为2:3，额外补碳量为理论合金成分碳含量的7.0％，低压烧结工艺制备的板状WC晶粒的WC-6Co硬质合金，记为试样T2G3，其横截面及纵截面的
Figure PCTCN2017117674-appb-000014
比值分别为1.37和0.32。横截面上的硬度约为92.6HRA,TRS＝3547MPa，断裂韧性为 19.95MPa*m 1/2；纵截面上的硬度为92.3HRA，TRS＝3562MPa，断裂韧性为19.57MPa*m 1/2。合金中板状WC的含量为75.0％。
该T2G3试样在不同截面上的XRD谱图见于图20～21，板状WC在合金中的排列取向程度列于表3，材料力学性能见于表4。
实施例8
本实施例步骤与实施例6基本相同，所不同之处在于步骤(1)中的颗粒大小为0.3μm的W原料与颗粒大小为5μm的W原料以重量比例为1:4，额外补碳量为理论合金成分碳含量的6.0％，低压烧结工艺制备的板状WC晶粒的WC-6Co硬质合金，记为试样T1G4，其横截面及纵截面的
Figure PCTCN2017117674-appb-000015
比值分别为1.78和0.31。横截面上的硬度约为92.7HRA,TRS＝3378MPa，断裂韧性为19.04MPa*m 1/2；纵截面上的硬度为92.0HRA，TRS＝3018MPa，断裂韧性为18.23MPa*m 1/2。合金中板状WC的含量为78.3％。
该T1G4试样在不同截面上的XRD谱图见于图22～23，板状WC在合金中的排列取向程度列于表3，材料力学性能见于表4。
表3.含板状WC晶粒WC-10Co硬质合金中板状WC的排列取向程度
Figure PCTCN2017117674-appb-000016
表4.含板状WC晶粒WC-6Co硬质合金的物理及力学性能
Figure PCTCN2017117674-appb-000017
Figure PCTCN2017117674-appb-000018
实施例9
(1)以WC-20wt.％Co为最终成分，选取颗粒大小为1.0μm的W原料与颗粒大小为25μm的W原料作为W粉的来源。按合金的理论成分计，W粉的组成由颗粒大小为1.0μm的W原料与颗粒大小为5μm的W原料以重量比例为4:1所共同组成，并称取与80μm大小的石墨粉及1.5μm的Co粉，额外补碳量为合金成分碳含量的8.0％。
(2)将上述W粉，石墨粉，Co粉置于行星式球磨机中进行10h低能量预球磨，球磨转速为120r/min，球料比为1:3，以实现粉末的均匀化分布及粉末颗粒之间的低强度结合，得到预球磨的W-C-Co粉末；
(3)随后将预球磨后的W-C-Co粉末置于等离子体辅助球磨机种进行6h的等离子体球磨，球料比为30:1，球磨转速为1200r/min，放电电流为2.0A，得到具有小尺度片层状W薄片与大尺度片层状W薄片相组合的W-C-Co复合粉末；小尺度片层状W薄片的长度处于0.4～1.2μm，厚度约为100～200nm。，大尺度片层状W薄片的的长度处于3.0～11.0um，厚度约为100～250nm。
(4)将步骤(3)中得到的含两种尺度大小相结合的片层状W薄片的W-C-Co复合粉末装入模具，采用单向轴压压制成型，压制压强为150Mpa，保压时间4min，随后脱模，得到粉末生坯。
(5)采用低压烧结工艺对生坯进行烧结。低压烧结工艺为：抽真空至1Pa后以升温速率为10K/min升温至1500℃，待温度达到最高温后，同时充入4.5MPa Ar气，保温30min，随后以20K/min的降温速度冷却至室温，得到板状WC晶粒的WC-20Co硬质合金，记为试样X4Y1，其横截面及纵截面的
Figure PCTCN2017117674-appb-000019
比值分别为0.96和0.33。横截面上的硬度约为89.1HRA,TRS＝4276MPa，断裂韧性为21.78MPa*m 1/2；纵截面上的硬度为89.2HRA，TRS＝4023MPa，断裂韧性为21.43MPa*m 1/2。合金中板状WC的含量为75.5％。
该X4Y1试样中的板状WC在合金中的排列取向程度列于表5，材料力学性能见于表6。
实施例10
本实施例步骤与实施例9基本相同，所不同之处在于步骤(1)中的颗粒大小为1.0μm的W原料与颗粒大小为25μm的W原料以重量比例为1:1，额外补碳量为理论合金成分碳含量的4.3％，低压烧结工艺制备的板状WC晶粒的 WC-20Co硬质合金，记为试样X1Y1，其横截面及纵截面的
Figure PCTCN2017117674-appb-000020
比值分别为1.82和0.27。横截面上的硬度约为89.4HRA,TRS＝4682MPa，断裂韧性为22.14MPa*m 1/2；纵截面上的硬度为89.2HRA，TRS＝4445MPa，断裂韧性为21.97MPa*m 1/2。合金中板状WC的含量为78.9％。
该X1Y1试样中的板状WC在合金中的排列取向程度列于表5，材料力学性能见于表6。
实施例11
本实施例步骤与实施例9基本相同，所不同之处在于步骤(1)中的颗粒大小为1.0μm的W原料与颗粒大小为25μm的W原料以重量比例为1:4，额外补碳量为理论合金成分碳含量的2.9％，低压烧结工艺制备的板状WC晶粒的WC-20Co硬质合金，记为试样X1Y4，其横截面及纵截面的
Figure PCTCN2017117674-appb-000021
比值分别为2.84和0.21。横截面上的硬度约为89.5HRA,TRS＝4398MPa，断裂韧性为22.85MPa*m 1/2；纵截面上的硬度为89.1HRA，TRS＝3814MPa，断裂韧性为21.45MPa*m 1/2。合金中板状WC的含量为82.4％。
该X1Y4试样中的板状WC在合金中的排列取向程度列于表5，材料力学性能见于表6。
表5.含板状WC晶粒WC-15Co硬质合金中板状WC的排列取向程度
Figure PCTCN2017117674-appb-000022
表6.含板状WC晶粒WC-20Co硬质合金的物理及力学性能
Figure PCTCN2017117674-appb-000023
Figure PCTCN2017117674-appb-000024
上述实施例为本发明较佳的实施方式，但本发明的实施方式并不受所述实施例的限制，其他的任何未背离本发明的精神实质与原理下所作的改变、修饰、替代、组合、简化，均应为等效的置换方式，都包含在本发明的保护范围之内。

Claims (7)

  1. 一种可调控板状WC晶粒排列状态的硬质合金的制备方法，其特征在于，包括以下步骤：
    (1)按WC-XCo的成分称量石墨粉、Co粉与W粉；其中W粉包括细小颗粒的W原料和粗大颗粒的W原料，其中6≤X≤20；
    所述细小颗粒的W原料的颗粒尺寸为0.3μm～1μm；所述粗大颗粒的W原料的颗粒尺寸为5μm～25μm；
    所述细小颗粒的W原料和粗大颗粒的W原料的重量比为1:4～4:1；
    (2)将步骤(1)的石墨粉、Co粉与W粉，并加入实际所需的额外碳量，置于行星式球磨机中进行行星式球磨，得到W-C-Co粉末；
    (3)将步骤(2)得到的W-C-Co粉末置于等离子体辅助高能球机中，进行等离子体辅助球磨，得到W-C-Co复合粉末；
    (4)将步骤(3)得到的W-C-Co复合粉末进行单向轴压压制成型，得到W-C-Co粉末生坯；
    (5)将W-C-Co粉末生坯于1350～1550℃中进行碳化烧结。
  2. 根据权利要求1所述的可调控板状WC晶粒排列状态的硬质合金的制备方法，其特征在于，步骤(1)所述石墨粉的颗粒尺寸为20μm～80μm。
  3. 根据权利要求1所述的可调控板状WC晶粒排列状态的硬质合金的制备方法，其特征在于，步骤(1)所述Co粉的颗粒尺寸为0.5μm～5μm。
  4. 根据权利要求1所述的可调控板状WC晶粒排列状态的硬质合金的制备方法，其特征在于，步骤(2)所述行星式球磨的具体参数为：
    球料比为1:3～1:5，球磨时间为5～10h。
  5. 根据权利要求1所述的可调控板状WC晶粒排列状态的硬质合金的制备方法，其特征在于，步骤(3)所述等离子体辅助球磨的具体参数为：球料比为30:1～60:1，球磨时间为3～6h，放电电流为1～3A。
  6. 根据权利要求1所述的可调控板状WC晶粒排列状态的硬质合金的制备方法，其特征在于，步骤(3)所述W-C-Co复合粉末，由小尺度片层状W薄片与大尺度片层状W薄片共同组成，所述小尺度片层状W薄片的长度为200nm～1.5μm，厚度为40nm-200nm；所述大尺度片层状W薄片的长度为3μm～15μm，厚度为60nm～300nm。
  7. 根据权利要求1所述的可调控板状WC晶粒排列状态的硬质合金的制备 方法，其特征在于，所述碳化烧结为真空烧结或低压烧结。
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