Surface coated cutting tool

Abstract

To provide a cutting tool having a base body improved in defect resistance and further improved in durability.SOLUTION: A cutting tool is provided, which contains 4.0 to 16.0 mass% of at least one kind out of Co and Ni, further contains 0.0 to 0.5 mass% of Cr, 4.0 to 12.0 mass% of one kind out of Ti, Ta, Nb, Zr, Hf and V, 6.0 to 7.5 mass%, with the remainder consisting of W and inevitable impurities, having a binder phase, a hard phase and a γ phase. In the cutting tool, the binder phase has the main component of Co and / or Ni, the hard phase has the main component of W carbide, and the γ phase has the main component of cubic crystal structure carbide of at least selected out of Ti, Ta, Nb, Zr, Hf and V, and having an average number of 0.5 to 5.0 of other binder phases in contact with each one of the binder phases in a cross-sectional region from the interface of the base body with a coating layer to the inner part of 10 μm on the inner side of the base body.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a surface-coated cutting tool having a coating layer and a substrate made of a WC-based cemented carbide. [Background technology]

[0002] WC-based cemented carbide is highly hard and has toughness, so cutting tools using it as a base exhibit excellent wear resistance and are known as cutting tools with long life. In recent years, various proposals have been made to further improve the cutting performance and tool life of cutting tools depending on the type of work material, cutting conditions, etc.

[0003] For example, Patent Document 1 describes a cutting tool made of a WC-based cemented carbide, in which the ratio of the area occupied by hexagonal Co to the area occupied by face-centered cubic Co in a cross-sectional region from the surface to a depth of 10 μm inside the substrate is more than 0.1 and not more than 0.3, and the cutting tool is said to have excellent chipping resistance, thermal cracking resistance, and wear resistance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-172697 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in consideration of the above circumstances and proposals, and has an object to provide a cutting tool having a base body with improved resistance to chipping during cutting. [Means for solving the problem]

[0006] The surface-coated cutting tool according to an embodiment of the present invention comprises: a substrate and a coating layer on the substrate; The substrate is 4.0 to 16.0 mass% of at least one of Co and Ni, 0.0 to 0.5 mass% of Cr, 4.0 to 12.0 mass% of at least one of Ti, Ta, Nb, Zr, Hf, and V; Contains 6.0 to 7.5 mass% C, the balance being W and inevitable impurities; having a binder phase, a hard phase and a γ phase; the binder phase is mainly composed of Co and / or Ni, The hard phase is mainly composed of W carbide, the γ phase is mainly composed of one or more cubic crystal structure carbides selected from Ti, Ta, Nb, Zr, Hf, W, and V; In a cross-sectional region extending from the interface between the substrate and the coating layer to a depth of 10 μm inside the substrate, the average number of the binder phase particles in contact with one of the binder phase particles is 0.5 to 5.0.

[0007] The cutting tool may satisfy the following (1).

[0008] (1) The area ratio of the binder phase is 10 to 25%. [Effects of the Invention]

[0009] The surface-coated cutting tool according to the embodiment has a substrate with improved resistance to chipping during cutting, and has further improved durability. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic diagram illustrating the number of other bonded phases in contact with one of the bonded phases. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present inventors have conducted extensive research to achieve the above-mentioned problem (object of the invention), and as a result have discovered that when the average number of binder phases in contact with one another in the vicinity of the substrate surface is within a predetermined range, the residual stress between the substrate and the coating layer is alleviated, the adhesion between the coating layer and the substrate is improved, and excellent chipping resistance is exhibited.

[0012] The present invention is based on this finding, and cutting tools according to embodiments of the present invention will be described below. In this specification and claims, when a numerical range is expressed as "L to M" (L and M are both numerical values), this is synonymous with "not less than L and not more than M," and the range includes an upper limit (M) and a lower limit (L), and the upper limit (M) and the lower limit (L) have the same units. Unless otherwise specified, the average value is an arithmetic average value.

[0013] 1. Substrate composition and structure The details of the composition and structure of the substrate of the cutting tool according to this embodiment are as follows. There are no restrictions on the shape of the base body as long as it is the shape of a cutting tool.

[0014] (1) Co and Ni One or both of Co and Ni are contained, and the total content of at least one of Co and Ni is preferably 4.0 mass % or more and 16.0 mass % or less. The reason is that if this content is satisfied, the plastic deformation resistance is excellent when used as a cutting tool substrate.

[0015] Here, Co and Ni are present in a binder phase having crystal grains with an FCC structure or an HCP structure, and are the main components of the crystal grains of the binder phase, i.e., the total of Co and Ni accounts for 50 atomic % or more of all components constituting the binder phase.

[0016] The binder phase may contain W and C, which are components of the hard phase, one or more of Cr, Ti, Ta, Nb, Zr, Hf, and V, which are contained in the γ phase, and unavoidable impurities. When these elements are present in the binder phase, they are presumed to be in a solid solution state in the binder phase. The method for identifying the bonded phase will be described later.

[0017] The mean free path (MFP) of the binder phase is often determined by the intercept method using the Fullman equation. However, in this embodiment, the MFP of the binder phase is determined using a value calculated from the EBSD analysis results. A method for determining the MEP, which is the thickness of this binder phase, is introduced in, for example, the following reference 1. Reference 1: Suzuki Hisashi, ed. "Cemented Carbide and Sintered Hard Materials - Fundamentals and Applications" Maruzen Co., Ltd. February 20, 1986

[0018] That is, the MFP was defined as the diameter (median diameter) when the cumulative area ratio of the diameters of circles having an area equal to each divided binder phase within the EBSD measurement range reached 50%. That is, a graph was plotted with the equivalent circle diameter on the horizontal axis and the cumulative area ratio on the vertical axis, and the MFP was defined as the equivalent circle diameter when the cumulative area ratio reached 50%. In addition, in a cemented carbide substrate, the binder phase forms a three-dimensional network and forms large domains, and in the substrate of this embodiment, each divided binder phase within the field of view is treated as a single binder phase.

[0019] The MFP of the binder phase of this embodiment is not particularly limited, but is preferably 0.3 μm or more and 1.0 μm or less. The reason for this is that if the MFP is less than 0.3 μm, slippage is likely to occur via the binder phase during cutting, resulting in insufficient resistance to plastic deformation and chipping, while if the MFP is more than 1.0 μm, sufficient wear resistance cannot be obtained.

[0020] It is more preferable that the area ratio of the binder phase in a longitudinal section (a section perpendicular to the substrate surface treated as if there were no minute irregularities on the substrate surface) is 10 to 25%. When the area ratio of the binder phase is within this range, the above-mentioned problems can be more reliably solved.

[0021] (2)Cr Cr is an optional component and may not be contained, so the Cr content is 0.0 mass % or more and 0.5 mass % or less. Cr dissolves in the binder phase, inhibits the growth of W carbides contained mainly in the hard phase, refines the W carbides, and makes the W carbides contained in the substrate fine-grained and homogeneous, thereby improving the substrate's toughness and resistance to plastic deformation. This function is impaired if the content exceeds 0.5 mass%, causing precipitation of composite carbides of Cr and W in the binder phase, reducing the substrate's toughness, and there is a risk that these carbides will become base points for chipping.

[0022] (3) Ti, Ta, Nb, Zr, Hf, V It is preferable to contain at least one element selected from Ti, Ta, Nb, Zr, Hf, and V (hereinafter, these may be collectively referred to as M) in a total amount of 4.0 mass% or more and 12.0 mass% or less. If the content of these elements is less than 4.0 mass%, oxidation resistance is insufficient, and significant wear occurs due to oxidation of the hard phase during cutting, leading to the end of the steel's life. On the other hand, if the content of these elements exceeds 12.0 mass%, toughness is insufficient, and chipping is likely to occur.

[0023] The M component exists in the γ phase as carbide grains and is included as the main component of the γ phase grains. "Main component" means that the carbides of the M component account for 50 atomic % or more of all the components that make up the γ phase. In addition to this carbide, the γ phase may also contain W and C contained in the hard phase, Co and Ni contained in the binder phase, and unavoidable impurities. The method for identifying the γ phase will be described later.

[0024] There are no particular restrictions on the average grain size (d50) of the γ phase, but it is preferably 1.0 μm or more and 3.0 μm or less. The reason for this is that if the average grain size is less than 1.0 μm, the γ phases are likely to slip during cutting, resulting in insufficient resistance to plastic deformation and chipping, while if the average grain size exceeds 3.0 μm, sufficient wear resistance cannot be obtained.

[0025] The average grain size (d50) of the γ phase refers to the equivalent circle diameter, i.e., the diameter (median diameter) when the cumulative area ratio of the diameter of a circle having an area equal to that of the γ phase is 50%. In other words, when a graph is plotted with the equivalent circle diameter on the horizontal axis and the cumulative area ratio on the vertical axis, the equivalent circle diameter is the diameter when the cumulative area ratio is 50%. The same definition of the average grain size (d50) applies hereinafter.

[0026] (4) C C is contained to form carbides, and is mainly contained in the hard phase and γ phase. Its content is preferably 6.0 mass% or more and 7.5 mass% or less, and if the amount of C is adjusted within this content range from the contents of the M component and W so that free carbon and η phases such as W3Co3C do not exist in the substrate, a sufficient amount of carbides can be formed in the hard phase and γ phase.

[0027] (5) W W exists in the hard phase as carbide grains, and is the main component of the hard phase, i.e., W carbide (mostly WC, but not limited to the stoichiometric composition) accounts for 50 atomic % or more of all components that make up the hard phase. The hard phase may contain binder phase components, gamma phase components, Cr, and unavoidable impurities that are inevitably mixed in during the manufacturing process. In addition, the crystal structure of the hard phase is an HCP structure, which is different from the crystal structure of the gamma phase, which has an FCC crystal structure. The method for identifying the hard phase will be described later.

[0028] The average grain size of the hard phase (average grain size when viewed over the entire substrate, d50) is preferably 0.8 μm or more and 6.0 μm or less. If the average grain size is less than 0.8 μm, the propagation of cracks during cutting cannot be sufficiently suppressed, while if it is 6.0 μm or less, plastic deformation resistance can be ensured and sufficient plastic deformation resistance is exhibited.

[0029] (6) Inevitable impurities As described above, the hard phase, γ phase, and binder phase may contain impurities that are inevitably (unintentionally) mixed in during the manufacturing process, and the amount of such impurities is preferably 0.3% by mass or less, with the entire substrate being 100% by mass.

[0030] (7) The average number of bonding phases in contact with one bonding phase in a cross-sectional area 10 μm from the interface between the substrate and the coating layer toward the substrate side. In a cross-sectional region extending from the interface between the substrate and the coating layer to a depth of 10 μm toward the substrate interior, the average number of other binder phases in contact with each binder phase is preferably 0.5 to 5.0. When this average number is 0.5 to 5.0, the residual stress between the substrate and the coating layer is alleviated by twin deformation and plastic deformation in the binder phase, improving the adhesion between the coating layer and the substrate, and exhibiting excellent chipping resistance and fracture resistance.

[0031] Here, other binder phases in contact with one binder phase refer to a situation in which it is possible to visually recognize that a certain binder phase and another binder phase share an interface when measured by EBSD at a magnification of 2000. In the cross-sectional region, the total number of binder phases within the field of view is used as the denominator and the sum of the number of other binder phases in contact with one binder phase is used as the numerator, which is the average number of other binder phases in contact with one binder phase.

[0032] This will be explained using the schematic diagram shown in Figure 1. Six bonding phases are depicted in Figure 1. The number written next to each bonding phase indicates the number of other bonding phases to which that bonding phase is adjacent. In the example shown in Figure 1, the total number of bonding phases is six, and the total number of other bonding phases adjacent to one bonding phase is 12 (= 0 + 2 + 3 + 3 + 3 + 1), so the average number of other bonding phases adjacent to one bonding phase is 2 (= 12 / 6).

[0033] 2. Methods for distinguishing between binder phase, hard phase, and γ phase, and measuring particle size distribution The binder phase, γ phase, and hard phase are distinguished and the particle size distribution of the hard phase is measured as follows.

[0034] (1) Cross section to be observed The vertical cross section of the cutting tool is smoothed by removing minute irregularities on the surface so that it does not interfere with measurement by Electron Backscatter Diffraction Pattern (EBSD) described later. The processing to obtain a smooth cross section is carried out using, for example, a focused ion beam device (FIB device).

[0035] (2) Determining the reference position The point closest to the intersection of the extension of the flank face and the extension of the rake face is defined as the cutting edge ridge, and the position moved 150 μm along the rake face from this cutting edge ridge is defined as the reference position.

[0036] (3) Determination of the substrate surface A 72 μm long range perpendicular to the cutting edge ridge is set with this reference position as the center, and the convex parts of the substrate surface within this range (the upper parts of the convex parts are the coating layer) are connected with line segments. A straight line is then drawn across the line connecting these convex parts so that the areas of the substrate above and below the line are equal. This straight line is treated as the substrate surface.

[0037] (4) Observation field A rectangular observation field is set on the substrate surface, centered on the reference position, with a width of 72 μm and a length of 10 μm extending perpendicular to the substrate surface toward the interior of the substrate. The sample is tilted 70 degrees around the 10 μm short side of the observation field as the axis. Observation is performed at a magnification of 2000x so that the set observation field can be observed in its tilted state.

[0038] It is preferable to observe at least 300 bonding phases in an observation field. If 300 bonding phases cannot be observed in one observation field, observation fields of the same size are set at positions 150 μm or more apart in the width direction, and the number of observation fields is increased until 300 bonding phases can be observed.

[0039] (5) Measurement The following measurements are performed on the observation field.

[0040] 1) Observe using a field emission scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS) and an EBSD measurement device (e.g., AMETEK OIM Data Collection) at an accelerating voltage of 15 kV with a measurement point spacing of 0.1 μm, and capture the EBSD pattern and EDS data simultaneously.

[0041] 2) Next, the measurement data is read into software for analyzing EBSD measurement results, such as EDAX / TSL OIM Analysis ver. 7.3.1, and the EDS count values ​​obtained from each measurement point inside the crystal grain corresponding to each element for all crystal grains within the observation field are averaged to obtain the EDS measurement value for each element in each crystal grain. The composition of each crystal grain is then derived from the obtained measurement values. In addition, with this software example, the average number of other bonded phases in contact with one bonded phase according to the above definition can be calculated by performing the operation described below.

[0042] 3) The phases contained in each grain are identified according to the definitions of grains and phases described above. That is, the EBSD pattern shows an HCP structure, and the average of the EDS count values ​​of W detected at all measurement points identified as the HCP structure is calculated. Grains that give measurement points with a W count value higher than half of this average are considered to be included in the hard phase. Next, the average of the EDS count values ​​of Co and Ni detected at all measurement points identified as the FCC or HCP structure is calculated. Grains with measurement points identified as the FCC or HCP phase with EDS count values ​​of Co and Ni higher than the average are considered to be included in the binder phase, and grains with measurement points that are the remainder of the FCC phase are considered to be included in the γ phase.

[0043] 4) When adjacent measurement points are judged to be the same phase, if the difference in orientation obtained from each measurement point is 5 degrees or more, the boundary between those two measurement points is considered to be the phase interface.

[0044] 5) EDS measurements are again carried out for each of the phases identified as the hard phase, γ phase, and binder phase in 3) above, and it is confirmed that the crystal grains identified as the hard phase are made up of W carbides at 50 atomic % or more, the crystal grains identified as the γ phase are made up of M carbides at 50 atomic % or more, and the crystal grains identified as the binder phase are made up of Co and Ni combined at 50 atomic % or more. This procedure identifies the hard phase, γ phase, and binder phase. Based on the identified hard phase, γ phase, and binder phase, the average grain size and MFP of each are determined as described above, and the area ratio of the binder phase is calculated based on the area that the binder phase occupies in the observation field.

[0045] 6) Based on the results of step 5), export the grain file of the bonded phases from the software. Check either Neighbors: Count and IDs or Neighbors: Count, IDs and Misoritentations before exporting. The exported file stores the number of adjacent bonded phases for each bonded phase as the "Number of grains neighboring current grain." By averaging this value for all bonded phases within the observation field, the average number of other bonded phases adjacent to one bonded phase can be obtained.

[0046] If the number of binder phase particles in the observation field is less than 300, the reference position is reset to a position 300 μm away from the cutting edge ridge toward the rake face, and the observation field is determined and measured in the same way. Measurements are continued by shifting the reference position by 150 μm each time until the total number of binder phase particles in the observation field is 300 or more, and the number of grains neighboring current grains from each measured field is averaged to obtain the average number of other binder phase particles in contact with one binder phase.

[0047] 3. Measurement of the content of each component The contents of W, Co, Ni, Ti, Ta, Nb, Zr, Hf, V, Cr, and C are measured using an electron probe micro analyzer (EPMA). A sample whose longitudinal cross section has been ground and smoothed is inserted into the EPMA device and irradiated with an electron beam. The contained elements and their amounts are measured from characteristic X-rays obtained from three observation fields each measuring 100 μm (vertical) × 100 μm (horizontal), and the measurement results are averaged.

[0048] 4.Coating layer The cutting tool of this embodiment has a coating layer formed by a CVD (Chemical Vapor Depositon) method. There are no restrictions on the coating layer as long as it is a known coating layer. However, as will be described later in the manufacturing method, it is preferable that the coating layer includes an Al2O3 layer as a coating layer for increasing the number of other binder phases in contact with one of the binder phases.

[0049] 5. Manufacturing method The cutting tool of this embodiment can be manufactured, for example, by the following procedure.

[0050] (1) Blend with raw powder As raw material powders for sintering, WC powder, Co powder, Ni powder, Cr3C2 powder, TiC powder, TaC powder, NbC powder, ZrC powder, HfC powder, and VC powder, each with a Fischer diameter of 0.8 to 6.5 μm, are prepared, blended in a predetermined ratio, and mixed using a ball mill.

[0051] (2) Press molding and sintering The mixed powder is dried and press-molded at a pressure of, for example, 100 MPa so as to have the desired cutting tool shape after the cutting process. The press-molded body is sintered by holding it in a vacuum at a temperature in the range of 1380 to 1420°C for 1 hour.

[0052] (3) Post-processing After sintering, wet blasting is performed to induce orientation changes and phase transformations in the binder phase on the surface of the substrate. Wet blasting treatment is Pressure: 0.3 MPa Projection time: 60 seconds Medium: Spherical zirconia or alumina ceramic particles with an average particle size d50 (volume %) of 100 to 150 μm as measured by laser analysis. Examples can be given of The sintered body is then held at 1200°C for 2 hours in an Ar-1% H2 atmosphere, and then heat-treated in a vacuum atmosphere at 1220°C for 1 hour.Then, the sintered body is machined and ground to form the desired cutting tool shape.

[0053] (4) Coating layer formation An example of forming an Al2O3 coating layer at approximately 1000°C using the CVD method is described below. A TiN layer, TiC layer, TiCN layer, or other layer with a total thickness of 3.0 to 12.0 μm is formed by CVD at 870 to 920°C, and then the temperature is raised to 1000 to 1050°C, after which an Al2O3 layer with a thickness of 3.0 to 10.0 μm is formed. In the cooling process after the Al2O3 layer formation, the substrate is cooled at a rate of 1 to 3°C from 500 to 400°C. This causes stress due to the difference in thermal expansion coefficients between the coating layer and the substrate to act on the binder phase, inducing orientation changes within the binder phase, twinning deformation, and FCC to HCP transformation, resulting in an increase in the number of binder phases adjacent to one another. [Example]

[0054] The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0055] 1. Preparation of Examples The cutting tools of the examples were produced by the following procedure.

[0056] (1) Raw powder and blending process First, WC powder, Co powder, Ni powder, Cr3C2 powder, TiC powder, TaC powder, NbC powder, ZrC powder, HfC powder, and VC powder, each with a Fischer diameter of 0.8 to 6.5 μm, were prepared as raw powders for sintering. The Fischer diameter of each powder is shown in Table 1. These powders were blended in the blending ratios shown in Table 1 and mixed for 24 hours in a ball mill using cemented carbide balls at a rotation speed that resulted in catalyzing.

[0057] (2) Press molding and sintering The mixed powder was dried and press-molded at a pressure of 100 MPa to become CNMG120408-MA (tool shape manufactured by Mitsubishi Materials Corporation) after the cutting process, and then sintered at 1420°C for 1 hour in a vacuum.

[0058] (3) Post-processing After sintering, wet blasting was performed to induce local crystal orientation changes and phase transformations in the binder phase on the substrate surface. Wet blasting treatment is Pressure: 0.3 MPa Projection time: 60 seconds Medium: Spherical zirconia particles with an average particle diameter d50 of 150 μm measured by laser analysis So I went.

[0059] Subsequently, the sample was held at 1200°C for 2 hours in an Ar-1% H2 atmosphere, and then heat-treated in a vacuum atmosphere at 1220°C for 1 hour. The heat-treated sintered body was then machined and ground to form the shape of CNMG120408-MA.

[0060] (4) Coating layer formation The coating layer was formed using the CVD method under the conditions shown in Table 2. The type, thickness, and deposition temperature of each layer are shown in the table. In the cooling process after the Al2O3 layer was formed, the layer was cooled (slowly cooled) from 500°C to 400°C at a cooling rate of 1 to 3°C. By the above steps, cutting tools 1 to 6 of the examples shown in Table 3 (hereinafter referred to as Examples 1 to 6) were produced.

[0061] 2. Preparation of Comparative Example For comparison, a cutting tool of a comparative example was produced by the following procedure.

[0062] (1) Raw powder and blending process First, the same raw material powder as in the example was prepared as the raw material powder for sintering. These powders were blended in the blending ratios shown in Table 1 and mixed in a ball mill in the same manner as in the examples.

[0063] (2) Press molding and sintering The same procedure as in Example 1 was carried out.

[0064] (3) Post-processing After sintering, the hard phase on the surface of the substrate was crushed by wet blasting. Wet blasting treatment is Pressure: 0.2 MPa Projection time: 10 seconds Medium: Spherical zirconia particles with an average particle diameter d50 of 100 μm measured by laser analysis So I went. Subsequently, the temperature was raised to 1220° C. under vacuum and held there for 1 hour. The heat-treated sintered body was then machined and ground to form the shape of CNMG120408-MA.

[0065] (4) Coating layer formation A coating layer was formed using the CVD method under the conditions shown in Table 2, similar to those of the Examples. In the Examples, the Al2O3 layer was slowly cooled from 500 to 400°C after deposition, but in the Comparative Examples, the Al2O3 layer was air-cooled to room temperature without slow cooling. By the above steps, cutting tools 1' to 6' of the comparative examples shown in Table 3 (hereinafter referred to as Comparative Examples 1' to 6') were produced.

[0066] [Table 1]

[0067] In Table 1, "-" indicates that no compound was added.

[0068] [Table 2]

[0069] In Table 2, the first layer is in contact with the upper layer, and the layers are stacked in order, with the fourth layer being the outermost layer. The column for each layer shows, from left to right, the composition, average thickness, and deposition temperature of the coating layer, and "-" indicates that there is no corresponding layer.

[0070] [Table 3]

[0071] Examples 1 to 6 and Comparative Examples 1' to 6' all had a binder phase and a γ phase in addition to a hard phase, and the content of unavoidable impurities was 0.3% by mass or less, with the entire substrate being 100% by mass.

[0072] The following cutting tests were carried out on Examples 1 to 6 and Comparative Examples 1' to 6'. The results are shown in Table 3.

[0073] Cutting test: Intermittent turning of an alloy steel round bar with four equally spaced slits along the length Work material: JIS SCM440 (HB315) round bar (Four slits evenly spaced along the length) Cutting speed: 100m / min Cutting depth: 2.0 mm Feed: 0.5mm / rev Cutting time: 2.5 minutes Cutting tests were carried out four times for each sample, and the number of times that characteristic wear, fracture, and slight chipping occurred based on the cutting edge condition after the four cutting tests is recorded in Table 4. Minor chipping refers to chipping that does not interfere with the continuation of cutting work even if it occurs.

[0074] [Table 4]

[0075] According to the cutting test results shown in Table 4, the Examples exhibited excellent cutting performance without any chipping in all four cutting tests, whereas the Comparative Examples exhibited short tool life due to chipping in all four cutting tests.

Claims

1. 1. A surface-coated cutting tool having a substrate and a coating layer on the substrate, The substrate is 4.0 to 16.0 mass% of at least one of Co and Ni, 0.0 to 0.5 mass% of Cr, 4.0 to 12.0 mass% of one or more of Ti, Ta, Nb, Zr, Hf, and V; Contains 6.0 to 7.5 mass% C, the balance being W and inevitable impurities; having a binder phase, a hard phase and a γ phase; The binder phase is mainly composed of Co and / or Ni, The hard phase is mainly composed of W carbide, the γ phase is mainly composed of at least one cubic crystal structure carbide selected from Ti, Ta, Nb, Zr, Hf, W, and V; In a cross-sectional region extending from the interface between the substrate and the coating layer to a depth of 10 μm toward the substrate interior, the average number of the binder phase particles in contact with each other binder phase is 0.5 to 5.

0. A surface-coated cutting tool characterized by:

2. 2. The surface-coated cutting tool according to claim 1, wherein the area ratio of the binder phase is 10 to 25%.

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