Classifications

• • 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
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C27/00—Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
  • C22C27/04—Alloys based on tungsten or molybdenum
• • 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

Definitions

• the present invention relates to a WC-based cemented carbide.
• WC-based cemented carbide is used, for example, as a substrate for a cutting tool, or a substrate for a surface-coated cutting tool (hereinafter sometimes referred to as a coated tool).
• the coated tool has a coating layer formed by vapor deposition of an Al 2 O 3 layer or a TiCN layer on a base body, and is used for cutting carbon steel, cast iron, alloy steel, and the like.
• Patent Document 1 describes a WC-based cemented carbide alloy that has a hard phase containing tungsten carbide particles and a binder phase whose main component is an iron-group element including cobalt, and that satisfies B/A ⁇ 0.05, where A is the number of tungsten carbide particles and B is the number of tungsten carbide particles that have one or less contact points with other tungsten carbide particles, and the alloy is said to have excellent resistance to plastic deformation.
• Patent Document 2 describes a WC-based cemented carbide having a Co content of 10 to 13 mass%, a ratio of Cr content to Co content of 2 to 8%, at least one of TaC and NbC in an amount of 0.2 to 0.5 mass%, and the remainder being WC, a hardness of 88.6 to 89.5 HRA, a ratio D 80 /D 20 of the WC cumulative grain size 80% diameter D 80 to the cumulative grain size 20% diameter D 20 being 2.0 ⁇ D 80 /D 20 ⁇ 4.0, the D 80 being 4.0 to 4.86 ⁇ m, and a WC adhesion degree c being 0.36 ⁇ c ⁇ 0.43, and the WC-based cemented carbide is said to have excellent chipping resistance.
• Patent No. 6256415 Patent No. 6774645
• the present invention has been made in consideration of the above circumstances and proposals, and aims to provide a WC-based cemented carbide that provides excellent resistance to plastic deformation and chipping resistance, particularly when used as a base for cutting tools and coated tools.
• the WC-based cemented carbide according to one embodiment of the present invention is Co: 6.0 to 10.0 mass%, Cr: 0.08 to 0.90 mass% (wherein Cr content (mass%)/Co content (mass%) is 10% or less), M: 0.0 to 3.8 mass% (M is one or more of V, Ta, Nb, Ti, and Zr), C: 4.5 to 7.5 mass%, and the balance being W and inevitable impurities, having a binder phase, a hard phase and a ⁇ phase; the binder phase is mainly composed of Co, the hard phase is mainly composed of W carbide, and the ⁇ phase is mainly composed of M carbide; In the crystal grains constituting the hard phase, the cumulative particle number 99% particle diameter C99 ( ⁇ m) is 3.30 or less, and the ratio of the cumulative particle number 99% particle diameter C99 ( ⁇ m) to the cumulative particle number 50% particle diameter C50 ( ⁇ m), C99/C50, is 4.80 or more and 6.50 or less, The ratio (L) of the interface length in contact with
• the WC-based cemented carbide may satisfy the following (1).
• the WC-based cemented carbide according to the above embodiment provides excellent resistance to plastic deformation and chipping, particularly when used as a substrate for cutting tools and coated tools.
• the inventors conducted extensive research into cemented carbide alloys that provide excellent resistance to plastic deformation and chipping when used as the substrate of a coated tool, and first recognized the following points (1) and (2) regarding the WC-based cemented carbide alloys described in the above-mentioned Patent Documents 1 and 2.
• the WC-based cemented carbide described in Patent Document 1 reaches the end of its tool life early when subjected to intermittent cutting.
• the WC-based cemented carbide described in Patent Document 2 lacks resistance to plastic deformation when subjected to high-speed, high-feed cutting.
• the present inventors have further conducted intensive research and have obtained the following findings, which have led to the present invention.
• (a) The plastic deformation resistance of a WC-based cemented carbide varies depending on the grain size of the crystal grains constituting the hard phase, and the smaller the grain size, the more the plastic deformation resistance of the WC-based cemented carbide is improved. Therefore, by making the WC-based cemented carbide contain a larger amount of crystal grains constituting the hard phase with a small grain size than before, the plastic deformation resistance is improved.
• (b) By appropriately dispersing the crystal grains constituting this hard phase in the WC-based cemented carbide and suppressing contact between the crystal grains constituting the hard phase, stress concentration at the contact points is suppressed and chipping resistance is improved.
• the WC-based cemented carbide according to the embodiment of the present invention will be described in detail to explain the present invention.
• the range includes an upper limit value (B) and a lower limit value (A)
• the unit of the upper limit value (B) and the lower limit value (A) are the same.
• the composition of a compound not expressed by a formula is not limited to a stoichiometric composition, and includes all compositions of conventionally known atomic ratios.
• composition of WC-based cemented carbide is: Co: 6.0 to 10.0 mass%, Cr: 0.08 to 0.90 mass% (however, the Cr content (mass%)/Co content (mass%) is 10% or less), M: 0.0 to 3.8 mass% (M is one or more of V, Ta, Nb, Ti and Zr), C: 4.5 to 7.5 mass%, with the balance being W and unavoidable impurities.
• Co 6.0 to 10.0 mass%
• Cr 0.08 to 0.90 mass%
• M 0.0 to 3.8 mass%
• M is one or more of V, Ta, Nb, Ti and Zr
• C 4.5 to 7.5 mass%, with the balance being W and unavoidable impurities.
• the WC-based cemented carbide has excellent resistance to plastic deformation when used as a coated tool or a tool substrate for a coated tool.
• Co is mainly present in the binder phase and is the main component of the binder phase (occupying 50 atomic % or more of all components contained in the binder phase).
• the binder phase is composed of crystal grains having an fcc structure and an hcp structure.
• the Co content is more preferably 7.0 to 9.6 mass %.
• the Cr content (mass%)/Co content (mass%) is set to 10% or less, and since the upper limit of the Co content is 10.0% by mass, the upper limit of the Cr content is set to 0.90% by mass to allow for some leeway.
• M one or more selected from V, Ta, Nb, Ti, and Zr
• M may not be contained (the content may be 0.0 mass%), but if it is contained, it dissolves in Co, which is the main component of the binder phase, and acts to increase the hardness of the WC-based cemented carbide.
• M forms carbides (not limited to stoichiometric composition) and becomes the main component of the ⁇ -phase (M accounts for 50 atomic % or more of all components contained in the ⁇ -phase). If the content exceeds 3.8 mass%, it reduces the toughness of the WC-based cemented carbide and becomes the starting point of chipping, so the upper limit of the M content is set to 3.8 mass%.
• C C is contained to form carbides, and is mainly contained in the hard phase and the ⁇ phase. If the C content is 4.5 mass% or more and 7.5 mass% or less, an adequate amount of carbides is formed in the hard phase and the ⁇ phase.
• W W is the main component of the hard phase. That is, W accounts for 50 atomic % or more of all components contained in the hard phase. W exists mainly as carbides (mostly WC, but including W carbides not limited to the stoichiometric composition) in the hard phase.
• Raw materials may contain unintended impurities, and there is a possibility that unintended impurities may be mixed in during the manufacturing process. These impurities are called unavoidable impurities.
• the content of the unavoidable impurities is preferably 0.3% by mass or less when the entire WC-based cemented carbide is taken as 100% by mass.
• Structure WC-based cemented carbide has a binder phase, a hard phase, and a ⁇ phase.
• a free carbon phase, an ⁇ phase, etc. may occur unintentionally.
• the constituents of each of the binder phase, the hard phase, and the ⁇ phase are expressed as crystal grains, and the size of each of the crystal grains is expressed as the crystal grain size.
• the crystal grain size refers to the circle equivalent diameter.
• Binder phase The binder phase is composed of crystal grains that contain Co as the main component, and may contain W and C as the hard phase components, M and Cr contained in ⁇ phase, and inevitable impurities.When these components other than Co exist in the crystal grains that constitute the binder phase, they are considered to be in a solid solution state. These crystal grains have fcc structure and hcp structure. The method of identifying the crystal grains that constitute the binder phase will be described later.
• the hard phase is composed of crystal grains that are mainly composed of W carbide and may contain binder phase components, ⁇ phase components, Cr and inevitable impurities. These crystal grains have a hcp structure. The method for identifying the crystal grains that compose the hard phase will be described later.
• the cumulative particle number 99% particle diameter C99 ( ⁇ m) to the cumulative particle number 50% particle diameter C50 ( ⁇ m) of the crystal grains constituting the hard phase is preferably 4.80 or more and 6.50 or less.
• C99/C50 is less than 4.80, the fine crystal grains constituting the hard phase are insufficient, and the plastic deformation resistance is reduced, while if it exceeds 6.50, the grain size difference (grain size difference) between the coarse crystal grains and the fine crystal grains constituting the hard phase is enlarged, and the crystal grains constituting the hard phase become too large, and the plastic deformation resistance of the WC-based cemented carbide is reduced.
• C99/C50 is more preferably 5.30 or more and 6.30 or less.
• the value of C50 is preferably 0.68 ⁇ m or less, and more preferably 0.60 ⁇ m or less.
• the lower limit of the cumulative particle number 50% particle diameter C50 ( ⁇ m) is about 0.38 ⁇ m.
• the cumulative particle number 50% particle diameter C50 ( ⁇ m) is preferably 0.38 to 0.68, and more preferably 0.38 to 0.60.
• the cumulative particle number 99% particle diameter C99 ( ⁇ m) is preferably 3.30 ⁇ m or less. If it exceeds 3.30 ⁇ m, the plastic deformation resistance of the WC-based cemented carbide decreases.
• the cumulative particle number 99% particle diameter C99 ( ⁇ m) is more preferably 3.20 ⁇ m or less.
• the lower limit of the cumulative particle number 99% particle diameter C99 ( ⁇ m) is about 2.50 ⁇ m.
• the cumulative particle number 99% particle diameter C99 ( ⁇ m) is preferably 2.50 to 3.30, and more preferably 2.50 to 3.20.
• the crystal grains constituting the hard phase are in contact with the crystal grains constituting the binder phase, the ⁇ phase, and other hard phases.
• the ratio (L) of the interface length in contact with the crystal grains constituting the binder phase to the total interface length of the crystal grains constituting the hard phase is 35% or more. If this ratio is less than 35%, the contact between the crystal grains constituting the hard phase increases, which makes it easier for stress concentration to occur, and the chipping resistance of the WC-based cemented carbide decreases.
• L is 40% or more.
• there is no particular restriction on the upper limit value of L but when manufactured according to an example of the manufacturing method described later, the upper limit value is about 55%. That is, L is preferably from 35 to 55%, and more preferably from 40 to 55%.
• the ⁇ phase is mainly composed of carbides of M (not limited to the stoichiometric composition), and may contain binder phase components, hard phase components, Cr, and inevitable impurities.
• the ⁇ phase is composed of crystal grains having an fcc structure. The method of identifying the crystal grains that compose the ⁇ phase will be described later.
• the WC-based cemented carbide preferably has a Rockwell hardness (HRA) of 88.8 to 90.4. If the Rockwell hardness falls within this range, the plastic deformation resistance and chipping resistance are more reliably improved.
• the Rockwell hardness (HRA) is measured in accordance with ISO 3738-1:1982 and ISO 3738-2:1988.
• any surface or cross section of a cemented carbide alloy is machined to remove any fine irregularities so as not to interfere with EBSD measurement, making it smooth.
• multiple fields of view e.g., two fields of view
• each field of view being, for example, 90 ⁇ m (vertical) ⁇ 120 ⁇ m (horizontal).
• SEM field emission scanning electron microscope
• EDS energy dispersive X-ray spectrometer
• EBSD measurement device e.g., OIM Data Collection manufactured by AMETEK
• a focused ion beam device For surface or cross-sectional processing, a focused ion beam device (FIB device) is used, for example.
• FIB device focused ion beam device
• the measurement data is read into software for analyzing the EBSD measurement results, for example, OIM Analysis ver. 7.3.1 manufactured by EDAX/TSL, and for each crystal grain, the EDS count values obtained from each measurement point inside the crystal grain corresponding to each element are averaged to obtain the EDS measurement value for each element of each crystal grain, and the composition of each crystal grain is derived from the obtained measurement values.
• the hard phase is an aggregate of crystal grains that are identified as having an hcp structure from the EBSD pattern and in which W carbide accounts for 50 atomic % or more.
• the binder phase is identified as an aggregate of crystal grains having an hcp crystal structure or an fcc crystal structure, but since the ⁇ phase is also identified as an aggregate of crystal grains having an fcc crystal structure, it is not possible to distinguish between the two based on the EBSD measurement results alone.
• the aggregate of crystal grains having an EDS count value of M (V, Ti, Nb, Ta, or Zr) obtained by EDS measurement is defined as the ⁇ phase
• the remaining aggregate of crystal grains identified as an aggregate of crystal grains having an fcc crystal structure is defined as the binder phase.
• a graph is prepared in which the horizontal axis represents the particle diameter of the crystal grains constituting the hard phase, and the vertical axis represents the cumulative proportion of the number of crystal grains constituting the hard phase corresponding to each particle diameter on the horizontal axis ((cumulative number of the number of crystal grains constituting the hard phase up to each particle diameter)/(total number of crystal grains constituting the hard phase) ⁇ 100). Then, the cumulative particle number 50% particle diameter C50 ( ⁇ m) at which the cumulative number ratio becomes 50% and the cumulative particle number 99% particle diameter C99 ( ⁇ m) at which the cumulative number ratio becomes 99% are obtained for each observation field, and the results are arithmetically averaged to calculate C99/C50.
• any surface or cross section of a cemented carbide is machined to remove any fine irregularities so as not to interfere with EBSD measurement, making it smooth.
• multiple fields of view e.g., 4 or 5 fields of view
• SEM field emission scanning electron microscope
• EDS energy dispersive X-ray spectrometer
• EBSD measurement device e.g., OIM Data Collection manufactured by AMETEK
• the measurement data is read into software for analyzing the EBSD measurement results, for example, OIM Analysis ver. 7.3.1 manufactured by EDAX/TSL, and for each crystal grain, the EDS count values obtained from each measurement point inside the crystal grain corresponding to each element are averaged to obtain the EDS measurement value for each element of each crystal grain, and the composition of each crystal grain is derived from the obtained measurement values.
• the hard phase is an aggregate of crystal grains that are identified as having an hcp structure from the EBSD pattern and in which W carbide accounts for 50 atomic % or more.
• the binder phase is identified as an aggregate of crystal grains having an hcp crystal structure or an fcc crystal structure, but since the ⁇ phase is also identified as an aggregate of crystal grains having an fcc crystal structure, it is not possible to distinguish between the two based on the EBSD measurement results alone.
• the aggregate of crystal grains having an EDS count value of M (V, Ti, Nb, Ta, or Zr) obtained by EDS measurement is defined as the ⁇ phase
• the remaining aggregate of crystal grains identified as an aggregate of crystal grains having an fcc crystal structure is defined as the binder phase.
• the total interface length of the crystal grains constituting the hard phase and the interface length where the crystal grains constituting the hard phase and the crystal grains constituting the bonding phase come into contact are determined.
• software for analyzing the EBSD measurement results described above for example, OIM Analysis ver. 7.3.1 manufactured by EDAX/TSL, can be used.
• the measured values obtained for each of the multiple measurement fields are arithmetically averaged to calculate the ratio of the interface length between the crystal grains constituting the hard phase and the crystal grains constituting the bonding phase to the total interface length of the crystal grains constituting the hard phase.
• three observation fields of 100 ⁇ m (vertical) ⁇ 100 ⁇ m (horizontal) are set, and the components and their amounts are measured from the characteristic X-rays obtained from each observation field, and the arithmetic average value of the measurement results is calculated.
• the manufacturing method involves preparing a predetermined raw material powder, followed by (1) a mixing step, (2) a molding step, (3) a sintering step, (4) a finishing step, and an optional (5) coating step, which are described below in order.
• the first mixing step is a step for pre-pulverizing a part of the WC powder to be used in order to obtain a WC powder pulverized into fine particles.
• 20 to 50 mass% of the WC powder to be used is mixed using a known method such as an attritor or a ball mill.
• the preferred mixing conditions using an attritor are a rotation speed of 40 to 90 min -1 , an amount of carbide balls of 100 to 300 kg, and a mixing time of 70 to 240 minutes.
• the mixing time is set to 120 to 240 minutes.
• Second mixing step In the second mixing step, the remaining WC powder, binder phase powder, and ⁇ phase powder are added to the mixed powder from the first mixing step so as to obtain the composition of the WC-based cemented carbide to be produced, and mixed using a known method such as an attritor, a ball mill, etc.
• the preferred mixing conditions using an attritor are a rotation speed of 40 to 90 min -1 , an amount of cemented carbide balls of 200 to 500 kg, and a mixing time of 70 to 420 minutes.
• the mixing time is set to 240 to 420 minutes.
• the raw powder of WC-based cemented carbide that has undergone these two mixing steps contains a large amount of fine WC powder that has been pulverized by mixing and contributes to improving resistance to plastic deformation.
• the value of the cumulative particle number 50% particle diameter C50 for the crystal particles that make up the hard phase becomes small, and it is possible to set the value of the cumulative particle number 99% particle diameter C99 to the cumulative particle number 50% particle diameter C50, C99/C50, to 4.80 or more and 6.50 or less.
• the two-stage mixing causes new surfaces to form on the surfaces of the WC particles, making it easier for Co to exist around them and improving sinterability. Therefore, even if the upper limit temperature of the sintering process described below is set to a relatively low temperature of 1430°C, which can suppress the growth of the hard phase, it is possible to obtain a WC-based cemented carbide alloy in which Co is well distributed around the hard phase and the crystal particles that make up the hard phase are dispersed, and it is possible to make the cumulative particle number 99% particle size C99 3.30 ⁇ m or less and L 35% or more for the crystal particles that make up the hard phase.
• the raw material powder that has been subjected to the mixing step is molded into a substrate having a predetermined shape (for example, an insert shape of CNMG120408).
• the molding can be performed by press molding at a pressure of, for example, 100 MPa.
• Sintering process This is a process of sintering the molded raw material.
• the maximum holding temperature is set to 1350 to 1430°C, and the temperature is held in a vacuum atmosphere of 10 -1 Pa or less for 50 to 120 minutes to prevent excessive grain growth of the crystal grains constituting the hard phase.
• There is no restriction on the cooling rate but it is more preferable to cool from the maximum holding temperature to 1100°C to 1200°C at a cooling rate of 35°C/min. If the cooling rate is slower than this rate, the grain growth of the crystal grains constituting the hard phase may be promoted and coarsened even in the cooling process, so that the generation of coarse-grained WC due to abnormal grain growth of the crystal grains can be suppressed by cooling.
• the upper limit of the cooling rate was determined based on the limitations of the apparatus at the time of filing.
• the molded body that has undergone the sintering process is subjected to a grinding process to form a predetermined shape (an insert shape of CNMG120408 defined in ISO standard 1832:2017 can be exemplified, but is not limited to this, and may be a shape of a drill, milling cutter, end mill, etc.).
• a predetermined coating layer is formed by a known means.
• the WC-based cemented carbide of this embodiment can be used as a cutting tool by processing it into a substrate of a predetermined shape, but it can also be coated with a hard layer by a known method to form a surface-coated cutting tool.
• the raw material powder was WC powder having an average particle size as shown in Table 1; Co powder with an average particle size of 1.0 ⁇ m, Cr3C2 powder with an average particle size of 1.6 ⁇ m , TiC powder having an average particle size of 1.0 ⁇ m; TaC powder with an average particle size of 1.9 ⁇ m; NbC powder with an average particle size of 1.1 ⁇ m; ZrC powder with an average particle size of 1.2 ⁇ m; VC powder having an average particle size of 1.7 ⁇ m was prepared and compounded according to the compounding compositions shown in Table 1, A to G and A′ to E′.
• the average particle size of each raw material powder is a Fischer diameter measured by an air permeability method using a Fischer subsieve sizer.
• the WC powder that had been subjected to the first mixing step and the remaining WC powder that had not been subjected to the first mixing step were mixed for the mixing time shown in Tables 2 and 3.
• the raw material powder after the second mixing step was press-molded into an insert shape of CNMG120408 shape at a pressure of 100 MPa.
• Cutting condition 1 high speed, high feed cutting
• Work material SUS304 round bar with outer diameter of 100 mm
• Cutting speed 150 m/sec.
• Depth of cut 1.5 mm
• Feed per revolution 0.3 mm
• Cutting condition 2 Work material: SUS316 round bar with outer diameter of 100 mm Cutting speed: 150 m/sec. Depth of cut: 2.0 mm Feed per revolution: 0.2 mm Wet Cutting
• Cutting condition 3 Work material: SUS630 round bar with outer diameter of 100 mm Cutting speed: 120 m/sec. Depth of cut: 2.0 mm Feed per revolution: 0.15 mm Wet Cutting
• Cutting condition 4 (intermittent cutting) Workpiece: SUS304, regular hexagonal prism-shaped material with an outer diameter of 80 mm, cutting speed: 100 m/sec, cutting depth: 2.0 mm Feed per revolution: 0.3 mm

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• 2024
  • 2024-10-24 JP JP2025553407A patent/JPWO2025089337A1/ja active Pending
  • 2024-10-24 WO PCT/JP2024/037901 patent/WO2025089337A1/ja active Pending
  • 2024-10-24 CN CN202480062417.2A patent/CN122003512A/zh active Pending

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