Surface coated cutting tools

Abstract

Providing durable surface-coated cutting tools for high-speed cutting of stainless steel. [Solution] The layer comprises a diffusion layer region A in contact with the substrate ridge, a diffusion layer region B in contact with the non-substrate ridge, and a non-diffusion layer region selectively present on the surfaces of diffusion layer region A and diffusion layer region B. The average composition of the diffusion layer region A in atomic percent is 3-12% W, 3-12% Co, 10-30% C, 0.5-3% M1 (M1 is one or more of Nb and Ta), 20-50% N, 0-2% M2 (M2 is one or more of Zr and Cr), with the remainder being Ti and unavoidable impurities. The average composition of diffusion layer region B is 3-12% W, 3-12% Co, 10-30% C, 20-50% N, and 0-0.1% M3 (M3 is one or more of Nb, Ta, Zr, Cr), with the remainder being Ti and unavoidable impurities. Surface-coated cutting tools with an average composition of 40-60% N and the remainder being Ti and unavoidable impurities in the non-diffusive layer region.

Description

Technical Field

[0001] The present invention relates to a surface-coated cutting tool (hereinafter sometimes referred to as a coated tool).

Background Art

[0002] Conventionally, as a coated tool, for example, a coated layer formed on a substrate such as a tungsten carbide (hereinafter represented by WC) - based cemented carbide is known. And, by adjusting the composition, structure, crystal structure, etc. of this coated layer, a proposal has been made to obtain a coated layer with improved cutting performance including cutting of difficult-to-cut materials. As an example of this proposal, there is one that diffuses the substrate components into the coated layer.

[0003] For example, Patent Document 1 describes a surface-coated cutting tool provided with a coated layer composed of a first layer of titanium nitride, a second layer of titanium carbonitride, a third layer of titanium carbonate or titanium carbonitrate, and a fourth layer of aluminum oxide on the surface of a WC-based cemented carbide substrate, and at least W and Co among the components constituting the substrate are diffusely contained in the grain boundaries of the first layer and the second layer. The tool is said to have excellent wear resistance without interlayer peeling or chipping in the coated layer during cutting of mild steel.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made in view of the above circumstances and proposals, and aims to provide a surface-coated cutting tool that suppresses abnormal wear such as chipping and has durability even in high-speed cutting of various stainless steels where the cutting edge becomes high temperature (for example, if it is austenitic stainless steel, those with a cutting speed exceeding 200 m / min). [Means for solving the problem]

[0006] A surface-coated cutting tool according to an embodiment of the present invention is It comprises a substrate and a coating layer on the substrate, In the substrate ridge portion and the non-substrate ridge portion of the rest of the substrate, the average composition from the surface of the substrate to 10 μm inward is, It contains 5.0-10.0 mass% Co, 1.0-9.0 mass% MA (MA is one or more of Ti and Zr), 0.0-0.3 mass% Cr, 5.5-6.5 mass% C, 0.1-0.6 mass% N, and 2.0-6.0 mass% MB (one or more of Nb and Ta). The remainder is W and unavoidable impurities. It contains 9.0-18.0 mass% Co, 0.0-1.0 mass% MC (MC is one or more of Ti and Zr), 0.0-0.3 mass% Cr, 5.5-6.5 mass% C, 0.0-0.1 mass% N, and 0.0-1.0 mass% MD (one or more of Nb and Ta). The remainder is W and unavoidable impurities. In both the substrate ridge portion and the non-substrate ridge portion, the average composition of the region extending more than 10 μm from the surface of the substrate toward its interior is: It contains 5.0-10.0 mass% Co, 1.0-9.0 mass% ME (ME is one or more of Ti and Zr), 0.0-0.3 mass% Cr, 5.5-6.5 mass% C, 0.1-0.6 mass% N, and 2.0-6.0 mass% MF (MF is one or more of Nb and Ta). The remainder is W and unavoidable impurities. The coating layer consists of a first layer in contact with the substrate with an average thickness of 0.2 to 1.0 μm and a second layer in contact with the first layer. The first layer consists of three layer regions: a diffusion layer region A in contact with the substrate ridge, a diffusion layer region B in contact with the non-substrate ridge, and a non-diffusion layer region selectively present on the surfaces of the diffusion layer region A and the diffusion layer region B. The diffusion layer region A and the diffusion layer region B each extend from the interface with the substrate to a depth of 0.1 to 0.2 μm. The non-diffusive layer region A extends from the surface of the diffuse layer region A to contact with the second layer. The non-diffusive layer region B extends from the surface of the diffuse layer region B to contact with the second layer. In both the diffusion layer region A and the diffusion layer region B, the average grain size of the crystal grains from the interface of the substrate to 0.1 μm is 10 to 20 nm. The average composition of the diffusion layer region A is 3.0 to 12.0 atomic percent of W, 3.0 to 12.0 atomic percent of Co, 10.0 to 30.0 atomic percent of C, 0.5 to 3.0 atomic percent of M1 (M1 is one or more of Nb and Ta), 20 to 50 atomic percent of N, and 0.0 to 2.0 atomic percent of M2 (M2 is one or more of Zr and Cr), with the remainder being Ti and unavoidable impurities. The average composition of the diffusion layer region B is 3.0 to 12.0 atomic percent of W, 3.0 to 12.0 atomic percent of Co, 10.0 to 30.0 atomic percent of C, 20 to 50 atomic percent of N, and 0.0 to 0.1 atomic percent of M3 (where M3 is one or more of Nb, Ta, Zr, and Cr), with the remainder being Ti and unavoidable impurities. The average composition of the non-diffusive layer region contains 40-60 atomic% N, with the remainder being Ti and unavoidable impurities.

[0007] Furthermore, the surface-coated cutting tool according to the above embodiment may satisfy the following (1).

[0008] (1) The second layer is one or more layers consisting of carbides, nitrides, oxides, carbonites, carbonitrides, or carbonitrides (not limited to stoichiometric composition and including unavoidable impurities) containing one or more elements selected from the group consisting of elements from groups 4 to 6 of the periodic table and Al, and the average total thickness of these layers is 3.0 to 20.0 μm. [Effects of the Invention]

[0009] The surface-coated cutting tool according to the above embodiment has durability, suppressing abnormal wear such as chipping even in high-speed cutting operations on various types of stainless steel. [Brief explanation of the drawing]

[0010] [Figure 1] It is a schematic diagram for explaining the cutting edge ridge line and the substrate ridge line part.

Embodiments for Carrying Out the Invention

[0011] The present inventor conducted intensive studies to solve the above-described problems (achieve the object of the above-described invention). As a result, the following findings (1) to (7) necessary for deriving the present invention were obtained.

[0012] (1) In a coated tool, due to insufficient adhesion at the interface between the substrate and the coating layer, abnormal wear such as chipping occurs.

[0013] (2) In particular, making the adhesion at the interface between the substrate and the coating layer strong at the substrate ridge line part contributes to the durability of the coated tool.

[0014] (3) In order to make the adhesion at the interface between the substrate and the coating layer strong, it is preferable that there is a diffusion layer region where elements contained in the substrate are diffused in a predetermined portion on the substrate side of the coating layer in contact with the substrate.

[0015] (4) As the composition of the diffusion layer region, when at least one of Nb and Ta is contained in a predetermined amount in addition to W, Co, and C, particularly excellent adhesion to the substrate is provided.

[0016] (5) However, since there is an appropriate range for the contents of Nb and Ta contained in the substrate, the composition of the substrate cannot be determined only from the perspective of diffusing these elements.

[0017] (6) It is preferable that the coating layer in the portion in contact with the substrate is one obtained by diffusing the above-described elements after forming a Ti nitride film.

[0018] (7) In order to promote the diffusion of Nb and Ta from the substrate to the coating layer, making the crystal grains in a predetermined portion of the coating layer in contact with the substrate fine is effective for securing a diffusion path, and for that purpose, it is preferable to perform carburizing treatment before forming the coating layer.

[0019] The present invention will be described in more detail below with respect to a surface-coated cutting tool according to an embodiment of the present invention. Furthermore, when a numerical range is described as "L~M" in the claims or specification, this description is synonymous with "L or greater and M or less," and the range includes the numerical values ​​of both the upper limit (M) and the lower limit (L). Also, if a unit is specified only for the upper limit (M), then the upper limit (M) and the lower limit (L) have the same unit.

[0020] 1. Definition of the cutting edge ridge and the base ridge. The terms "cutting edge ridge" and "substrate ridge portion" as used in the claims and specification are as follows: As shown in Figure 1, the flank (1) and rake face (2) are approximated by straight lines, and the cutting edge ridge is found at the intersection point (3) where these lines intersect when extended. From this cutting edge ridge, the shortest possible line segment is drawn toward the substrate surface. At the intersection of this line segment and the substrate surface, 20 μm line segments are drawn perpendicular to this line segment in the direction of the flank (1) and rake face (2), respectively. The region (4) obtained by projecting these 20 μm line segments toward the substrate surface parallel to the shortest possible line segment is called the substrate ridge portion. Note that the coating layer is not shown in Figure 1.

[0021] 2.Base (1) Composition The composition described in this embodiment is such that, along the surface of the substrate, the average composition from the surface of the substrate towards the interior up to 10 μm is as follows: (Base ridge section) It contains 5.0-10.0 mass% Co, 1.0-9.0 mass% MA (MA is one or more of Ti and Zr), 0.0-0.3 mass% Cr, 5.5-6.5 mass% C, 0.1-0.6 mass% N, and 2.0-6.0 mass% MB (one or more of Nb and Ta). The remainder is W and unavoidable impurities (Non-basal ridge section) It contains 9.0-18.0 mass% of Co, 0.0-1.0 mass% of MC (MC is one or more of Ti and Zr), 0.0-0.3 mass% of Cr, 5.5-6.5 mass% of C, 0.0-0.1 mass% of N, and 0.0-1.0 mass% of MD (one or more of Nb and Ta). The remainder is W and unavoidable impurities That is the case.

[0022] Furthermore, in both the substrate ridge region and the non-substrate ridge region, the average composition in the region exceeding 10 μm from the substrate surface toward its interior (hereinafter sometimes referred to as the interior region) is: It contains 5.0-10.0 mass% Co, 1.0-9.0 mass% ME (ME is one or more of Ti and Zr), 0.0-0.3 mass% Cr, 5.5-6.5 mass% C, 0.1-0.6 mass% N, and 2.0-6.0 mass% MF (MF is one or more of Nb and Ta). The remainder is W and unavoidable impurities That is the case.

[0023] The following describes the components in the base ridge region, non-base ridge region, and internal region.

[0024] (a) Co The Co content is preferably 5.0 to 10.0 mass% in the substrate ridges and internal regions, and 9.0 to 18.0 mass% in the non-substrate ridge areas. This is because it exhibits excellent resistance to plastic deformation and excellent resistance to chipping when used as a base material for coated tools. Co is primarily present in the bonded phase and is the main component of the bonded phase (accounting for 50 atomic percent or more of all components in the bonded phase). The bonded phase is composed of crystal grains having either an hcp structure or an fcc structure.

[0025] (b)Cr In each region, it is preferable to include Cr in order to improve the resistance to plastic deformation without degrading the toughness of the substrate. That is, Cr solid-solves in the binder phase and solid-solution strengthens the binder phase. Although Cr may not be included, if it is included, it is preferable to limit the amount to 0.3% by mass.

[0026] (c) MA, MB, MC, MD, ME, and MF MA, MB, MC, MD, ME, and MF function to increase the hardness of the substrate by dissolving in Co, which is the main component of the bonding phase. In addition, MA, MB, MC, MD, ME, and MF form carbides (not limited to stoichiometric composition), and these carbides become the main components of the secondary hard phase (of all components contained in the secondary hard phase, carbides of MA, MB, MC, MD, ME, and MF with W account for 50 atoms or more).

[0027] The MA and ME content is preferably between 1.0% by mass and 9.0% by mass. If the MA and ME content is less than 1.0% by mass, the substrate's resistance to plastic deformation becomes insufficient. On the other hand, if the MA and ME content exceeds 9.0% by mass, the toughness of the substrate decreases.

[0028] To reduce the toughness of the substrate, it is preferable not to include MC and MD, but if they are included, the upper limit of the content should be 1.0 mass%.

[0029] If the MB and MF content is less than 2.0 mass%, the diffusion of Nb and Ta from the substrate into the diffusion layer region A adjacent to the substrate ridges will not occur sufficiently, and excellent adhesion between the coating layer and the substrate cannot be obtained. On the other hand, if the MB and MF content exceeds 6.0 mass%, the toughness of the substrate will decrease.

[0030] (d)C C is included to form carbides and carbonitrides, and if its content is between 5.5% by mass and 6.5% by mass, the appropriate amount of carbides and carbonitrides will be formed.

[0031] (e)N N is included to form carbonitrides. If the N content is between 0.1% by mass and 0.6% by mass in the substrate ridge area, an appropriate amount of carbonitrides will be formed, and if it is between 0.0% by mass and 0.1% by mass in the non-substrate ridge area, no excess carbonitrides will be formed.

[0032] (f)W W is the main component of the hard phase. That is, W accounts for 50 atomic percent or more of all components in the hard phase. W exists in the hard phase as carbides (mostly WC, but may include W carbides not limited to stoichiometric composition).

[0033] (g) Inevitable impurities Raw materials may contain unintended impurities, and unintended impurities may also be introduced during the manufacturing process. These impurities are called unavoidable impurities. The presence of unavoidable impurities does not affect the physical properties of the substrate. Preferably, the amount of unavoidable impurities is 0.3% by mass or less when the total amount of the aforementioned elements that determine the composition of the substrate is taken as 100% by mass.

[0034] (2) Shape The shape of the base material is not particularly restricted as long as it is a shape that can be used as a coating tool; the shape of the insert is an example.

[0035] 3.Coating layer The coating layer consists of a first layer in contact with the substrate and a second layer consisting of one or more other layers with different compositions placed on top of the first layer.

[0036] (1)First layer (1-1) Average thickness The average thickness of the first layer is preferably 0.2 to 1.0 μm. This is because if it is less than 0.2 μm, the adhesion of the first layer to the substrate is insufficient, and if it exceeds 1.0 μm, the thickness of the second coating layer is restricted, reducing the wear resistance of the coated tool. The measurement of the average thickness, as described later, may be performed on either the flank or the rake face, as long as it is not at the ridge line of the substrate (however, the measurement of the average thickness described later will be explained using the rake face).

[0037] (1-2) Layer structure of the first layer in the base ridge and non-base ridge regions The first layer consists of three layer regions: a diffusion layer region A adjacent to the substrate ridge, a diffusion layer region B adjacent to the non-substrate ridge, and a non-diffusion layer region selectively present on the surfaces of diffusion layer region A and diffusion layer region B. Here, "selective" means that it may or may not be present.

[0038] Furthermore, both diffusion layer region A and diffusion layer region B extend from 0.1 to 0.2 μm from the interface with the substrate, and when a non-diffusion layer region exists, it extends from the surface of diffusion layer region A or diffusion layer region B to contact with the second layer. In other words, diffusion layer region A and diffusion layer region B may be in direct contact with the second layer.

[0039] (1-2) Composition The average compositions of diffusion layer region A and diffusion layer region B are as follows:

[0040] (Diffusion layer region A) The average composition of diffusion layer region A is 3.0-12.0 atomic% of W, 3.0-12.0 atomic% of Co, 10.0-30.0 atomic% of C, 0.5-3.0 atomic% of M1 (M1 is one or more of Nb and Ta), 0.0-2.0 atomic% of M2 (M2 is one or more of Zr and Cr), and 20-50 atomic% of N, with the remainder being Ti and unavoidable impurities.

[0041] (Diffusion layer area B) The average composition of diffusion layer region B is 3.0-12.0 atomic% W, 3.0-12.0 atomic% Co, 10.0-30.0 atomic% C, 0.0-0.1 atomic% M3 (M3 being one or more of Nb, Ta, Zr, and Cr), and 20-50 atomic% N, with the remainder being Ti and unavoidable impurities.

[0042] (Non-diffusive layer region) The average composition of both non-diffusive layer region A and non-diffusive layer region B contains 40-60 atomic percent of N, with the remainder being Ti and unavoidable impurities.

[0043] The reasons for setting the average compositions of diffusion layer region A, diffusion layer region B, and non-diffusion layer region as described above are as follows.

[0044] (a)W, Co It is preferable that diffusion layer region A and diffusion layer region B contain 3.0 to 12.0 atomic percent of W and 3.0 to 12.0 atomic percent of Co. This is because if the content of W and Co is less than 3.0 atomic percent each, the amount of diffusion of these elements from the substrate is small, resulting in insufficient adhesion between the substrate and the coating layer. In the example manufacturing method described later, the maximum content of W and Co in diffusion layer region A and diffusion layer region B is 12.0 atomic percent each.

[0045] (b)C It is preferable that 10.0 to 30.0 atomic percent of carbon (C) be present in diffusion layer regions A and B. The reason for this is as follows: When 10 atomic percent or more of carbon (C) is present in diffusion layer regions A and B, the grain size of the crystal grains present in the interface region between the substrate and the coating layer becomes smaller, increasing the diffusion pathways for the substrate components and improving the adhesion between the substrate and the coating layer. However, if the carbon content exceeds 30.0 atomic percent, carbon becomes excessive, impairing the toughness of the coating layer and leading to a decrease in tool life.

[0046] (c) M1 (one or more of Nb and Ta) When M1 (one or more of Nb and Ta) is diffused in 0.5 atomic percent or more in the diffusion layer region A adjacent to the substrate edge, the coated tool exhibits particularly excellent peel resistance and fracture resistance. The reason for this is not entirely clear, but it is thought that the diffusion of heat-resistant Nb and Ta into the coating layer adjacent to the substrate edge, where the greatest stress is applied during cutting, maintains high adhesion between the substrate and the coating layer even at high temperatures caused by high-speed cutting of austenitic stainless steel, which has low thermal conductivity. There is no particular upper limit on the amount of M1 that can be diffused, but in one example of the manufacturing method described later, the maximum value of the M1 content in the diffusion layer region is 3.0 atomic percent.

[0047] (d) M2 (one or more of Zr and Cr) The aforementioned problem can be solved whether or not M2 (one or more of Zr and Cr) is present in diffusion layer region A, but if it is present, the upper limit should be 2.0 atomic percent. If M2 exceeds 2.0 atomic percent, the toughness of the coating layer decreases.

[0048] (e) M3 (M3 is one or more of Nb, Ta, Zr, and Cr) Whether or not M3 (one or more of Nb, Ta, Zr, and Cr) is present in diffusion layer region B, the aforementioned problem is solved. However, if it is present, the upper limit should be 0.1 atomic percent. If M3 exceeds 0.1 atomic percent, the toughness of the coating layer decreases.

[0049] (f)N N is included to form a Ti nitride film. If the N content is 20-50 atomic percent in diffusion layer region A and diffusion layer region B, and 40-60 atomic percent in the non-diffusion layer region, then an appropriate amount of Ti nitride will be formed in each region.

[0050] (g)Ti Ti forms nitrides (not limited to stoichiometric compositions).

[0051] (h) Inevitable impurities Even if unavoidable impurities are present, they do not affect the physical properties of the diffusion layer region A, diffusion layer region B, and non-diffusion layer region according to this embodiment.

[0052] (1-3) Average particle size The average grain size of the crystal grains in the diffusion layer region A and diffusion layer region B (collectively referred to as the interface region) from the interface between the substrate and the first layer up to 0.1 μm, that is, from the interface up to 0.1 μm in the direction perpendicular to the surface of the substrate (the thickness direction of the coating layer), is 10 to 20 nm (the definition of average grain size will be described later).

[0053] The reasons are as follows: When the average particle size exceeds 20 nm, there are not enough pathways for the elements contained in the substrate to diffuse into the first layer, making it impossible to maintain the specified content of W, Co, C, Nb, Ta, etc. in diffusion layer region A and diffusion layer region B. When the average particle size is smaller than 10 nm, the Ti nitride crystal grains become too fine, leading to an increase in grain boundaries and a decrease in the oxidation resistance of the coating layer, making it prone to abnormal damage.

[0054] While there are no particular restrictions on the average grain size of the crystal grains in diffusion layer region A, diffusion layer region B, and non-diffusion layer region, which exist outside the interface region, examples include 10 to 100 nm.

[0055] (1-4) Definitions of diffusion layer region A and diffusion layer region B Diffusion layer region A and diffusion layer region B are regions in which a predetermined element contained in the substrate is diffused. In the region from the interface between the substrate and the first layer (definition will be described later) to the interface between the first layer and the second layer, if there are 10 or more consecutive measurement points where one or more of the substrate components W, Co, Nb, Ta, C, Ti, and N are present at a concentration of 1.0 atomic% or more, then it is considered that the substrate components are diffused into the first layer, i.e., diffusion layer region A and diffusion layer region B exist in the first layer. The spacing between each measurement point is 2 nm.

[0056] In other words, diffusion layer region A and diffusion layer region B are regions in which W, Co, Nb, and Ta are present in concentrations of 1.0 atomic percent or more, starting from the interface between the substrate and the first layer and extending to a position where all W, Co, Nb, and Ta are present in concentrations of 0.1 atomic percent. The non-diffusion layer region extends from this 0.1 atomic percent position in the first layer to the second layer. This 0.1 atomic percent position does not have to be within the first layer, nor does it have to be within the second layer. In this case, the substrate components have diffused beyond the first layer to the second layer, and there is no non-diffusion layer region in the first layer; the first layer consists only of diffusion layer region A or diffusion layer region B.

[0057] Even if the substrate components have diffused to the second layer, this diffused region is only a small fraction of the entire second layer. Therefore, the amount of substrate components in the second layer is negligibly small, and it can be treated as if there are no diffusion layer regions A and B within the second layer.

[0058] The thickness of diffusion layer region A and diffusion layer region B (length from the interface) is preferably such that the average thickness is 0.1 μm or more and 0.2 μm or less in the thickness direction of the first layer from the interface between the substrate and the first layer. This is because if the average thickness is less than 0.1 μm, the adhesion between the substrate and the first layer is insufficient. The upper limit of the average thickness may be the thickness of the first layer (the non-diffusion layer region does not need to exist), but in one example of the manufacturing method described later, the maximum average thickness is 0.2 μm.

[0059] (2)Second layer The second layer is placed on top of the first layer and is not limited to one type of layer, but may consist of multiple types of layers. Preferably, the compounds constituting the second layer are compounds that have high adhesion to the first layer. Examples of such compounds with high adhesion include carbides, nitrides, oxides, carbonites, carbonitrides, and carbonitrides (not limited to stoichiometric composition, and including unavoidable impurities) containing one or more elements selected from the group consisting of elements from groups 4 to 6 of the periodic table and Al.

[0060] The combined thickness of the first and second layers is preferably 4.0 to 20.0 μm. This is because if the thickness is less than 4.0 μm, the effect of the coating layer is not fully realized, and if it exceeds 20.0 μm, the crystal grains of the coating layer tend to coarseen, making chipping more likely. Therefore, the combined thickness of the second layer can be exemplified as 3.0 to 20.0 μm.

[0061] (3) Compounds unintentionally present in each layer (compounds that may be unintentionally produced during the deposition of the first and second layers) In this embodiment, the first and second layers are formed so that no compounds other than the aforementioned compounds are present. However, when changing the layer to be formed, changes in pressure and temperature within the deposition apparatus inevitably occur, and unintended compounds different from the intended compounds may be formed. In other words, unintended compounds may exist in addition to the compounds with the composition described in the claims. However, even if these unintended compounds are present, the aforementioned problems to be solved are still resolved.

[0062] 4. Interface between the substrate and the first layer, and interface between the first layer and the second layer. The interfaces between the substrate and the first layer, and between the first layer and the second layer, are determined by cross-sectional observation using a scanning electron microscope (SEM). The longitudinal section (for inserts, a cross-section perpendicular to the substrate surface when the substrate surface is considered flat, assuming no surface irregularities; for shaft tools, a cross-section perpendicular to the shaft) is observed, and the brightness of the substrate, the first layer, and the second layer is measured at three locations each. When measuring brightness, the observation conditions are set so that (absolute value of the difference in brightness between the substrate and the first layer) / (brightness of the substrate) and (absolute value of the difference in brightness between the first layer and the second layer) / (brightness of the first layer) are 50% or more, and the locations where the difference in brightness appears are approximated by a straight line to be the respective interfaces.

[0063] 5. Average grain size of crystal grains in the interface region Experiments have shown that the average grain size of crystal grains in the interface region yields similar results regardless of whether the measurement is performed at the substrate edge, rake face, or flank face. Therefore, the average grain size of crystal grains in the interface region will be measured at the rake face.

[0064] The average grain size of the crystal grains in the interface region is measured as follows: Specifically, it is measured by cross-sectional observation using a transmission electron microscope (TEM) on the longitudinal section of the scoop face. Three or more observation fields are set up with a size of 0.1 μm (longitudinal: perpendicular to the substrate surface, i.e., the thickness direction of the coating layer) × 0.1 μm (horizontal: parallel to the substrate surface), with the interface between the substrate and the first layer as the lower end. The average grain size of the crystal grains in each observation region is measured using the section method. In the section method, four line segments of 0.1 μm are drawn horizontally at 0.1 μm intervals in the longitudinal direction of the target observation field. The total number of crystal grains crossed by these four line segments, n, is then measured. L We find n. In this case, we count the number of crystal grains whose ends are inside the line segment as (1 / 2). L Based on this value, the average particle size is 0.4 / n L It is expressed in μm. Then, the arithmetic mean of the average grain size obtained for each of the three or more observation fields is calculated and taken as the average grain size of the crystal grains in the interface region.

[0065] 6. Measurements related to diffusion layer region A and diffusion layer region B (1) Measurement of the average thickness of diffusion layer region A and diffusion layer region B The average thickness of diffusion layer region A and diffusion layer region B (hereinafter sometimes collectively referred to as the diffusion layer region) is measured as follows.

[0066] Linear analysis of the composition is performed using energy-dispersive X-ray spectroscopy (EDS) with a measurement length of 2.0 μm and a spacing of 2.0 nm between measurement points, starting from the interface between the substrate and the first layer in the thickness direction of the first layer. When there are 10 or more consecutive measurement points in the thickness direction of the interface coating layer between the substrate and the first layer, where one or more of the elements W, Co, Nb, and Ta are present at a concentration of 1.0 atomic percent or more, the first layer is considered to have a diffusion layer region. The interface between the diffusion layer region and the non-diffusion layer region is defined as the position where any of the substrate components W, Co, Nb, and Ta become less than 0.1 atomic percent by linear analysis. This is because the aforementioned problem cannot be solved if any of W, Co, Nb, or Ta are less than 0.1 atomic percent. Here, the atomic percentages for W, Co, Nb, and Ta represent the ratio (atomic percentage) of the number of atoms of each atom to the sum of the total number of atoms of W, Co, Nb, Ta, C, Ti, and N.

[0067] In this case, if there are no locations in the first layer where the number of atoms of any of W, Co, Nb, or Ta is less than 0.1 atomic percent, but there are locations in the second layer, then it is assumed that only a diffusion layer region exists in the first layer, and no non-diffusion layer region exists in the first layer. On the other hand, when there is a position in the first layer where the number of atoms of all elements W, Co, Nb, and Ta is less than 0.1 atomic percent, the distance from the interface between the substrate and the first layer to that position is defined as the thickness of diffusion layer region A and diffusion layer region B.

[0068] The thickness of diffusion layer region A is measured at four locations in the projected area centered on the cutting edge, at 10 μm and 20 μm in the flank direction and 10 μm and 20 μm in the rake direction, and the average thickness of diffusion layer region A is calculated by arithmetic mean. The thickness of diffusion layer region B is measured at five arbitrary locations in the longitudinal section of the rake face, and the average thickness of diffusion layer region B is calculated by arithmetic mean. It is preferable that the spacing between each EDS analysis line is 0.5 μm or more.

[0069] (2) Measurement of the composition of diffusion layer region A and diffusion layer region B The composition of diffusion layer region A and diffusion layer B is measured as follows: With the interface between the substrate and the first layer as the lower end, three or more observation fields are set up with a size of average thickness (vertical) of diffusion layer region A and diffusion layer B × 0.1 μm (horizontal: direction parallel to the substrate surface). EDS mapping is performed for each observation field, and the results are arithmetic mean to obtain the average composition of diffusion layer region A and diffusion layer B.

[0070] (3) Measurement of the composition of the non-diffusive layer region The non-diffusive layer region is measured as follows: Three or more observation fields, each 0.1 μm in size, are set parallel to the substrate surface, with the interface between the diffuse and non-diffusive layer regions as the lower end and the interface between the first and second layers as the upper end. EDS mapping is performed for each observation field, and the results are arithmetically averaged to obtain the average composition of the non-diffusive layer region.

[0071] 7. Average thickness of the first and second layers The average thickness of the first layer is defined as the distance between two interfaces, which are linearly approximated as described above: the interface between the substrate and the first layer, and the interface between the first layer and the second layer. This distance is measured at five points at a distance of 50 μm or more in a direction parallel to the interface between the substrate and the first layer, and the arithmetic mean is calculated. The average thickness of the second layer is defined as the distance between two interfaces: the interface between the first and second layers, which are linearly approximated, and the interface between the first and second layers and the surface of the second layer. The arithmetic mean of these distances is calculated by measuring five such distances at a distance of 50 μm or more in a direction parallel to the interface between the substrate and the first layer.

[0072] 8. Determination of the substrate composition (1) Determination of the composition of the base ridge portion The composition of the substrate ridge is measured using energy-dispersive X-ray spectroscopy (SEM-EDX). A cross section measuring 10 μm (vertical) × 40 μm (horizontal) is set as the observation field, parallel to the tangent to the substrate ridge, within the substrate at a depth of 10 μm. The composition of the substrate ridge is determined from the characteristic X-rays obtained.

[0073] (2) Determination of the composition of the non-substrate ridge portion The composition of the non-substrate ridge area is also measured using SEM-EDX. The longitudinal section of the substrate is processed to be smooth by removing fine irregularities so as not to interfere with EDX measurement. At arbitrary longitudinal sections 100 μm to 1 mm away from the cutting edge ridge along the flank and at arbitrary longitudinal sections in the region 100 μm to 1 mm away along the rake face, at least three observation fields of view (a total of six or more) with a size of 10 μm (length) × 40 μm (width) are set with the upper end of each field of view being the substrate surface (one side of one adjacent observation field and one side of the other observation field are parallel and the distance between them is 50 μm or more). The substrate composition is determined from the characteristic X-rays obtained by irradiating each observation field with an electron beam, and the composition of the non-substrate ridge area is determined by arithmetic mean taking the mean value.

[0074] (3) Determination of the composition inside the substrate The internal composition of the substrate is measured using an electron beam microanalyzer (EPMA). The longitudinal section of the substrate is processed to be smooth by removing any fine irregularities so as not to interfere with EPMA measurements. Three or more observation fields, each measuring 100 μm (length) x 100 μm (width), are set up in a region more than 500 μm inward from the surface of the substrate (one side of one adjacent observation field and one side of the other observation field are parallel, with a distance of 100 μm or more between them). The substrate composition is determined from the characteristic X-rays obtained by irradiating each observation field with an electron beam, and the average content is obtained by arithmetic mean.

[0075] 9. Manufacturing method (1) Substrate manufacturing process The following treatment is performed to achieve a predetermined composition in the substrate edge and non-substrate edge regions. The raw material powder is mixed to achieve a predetermined composition in the substrate interior, and the substrate is formed. Subsequently, a secondary hard phase is created by nitriding the secondary hard components (Ti, Nb, Ta, Zr) by nitriding during the heating process for sintering. Then, sintering is performed under a vacuum atmosphere, causing denitrification of the secondary hard phase present on the substrate surface, decomposition of the secondary hard phase, and diffusion of the secondary hard phase components into the substrate interior. As a result, in the non-substrate edge regions, areas where the secondary hard phase does not exist on the substrate surface are formed. However, in the substrate edge regions, denitrification is less likely to occur due to their shape, and diffusion of the secondary hard phase components also occurs from the scoop face and flank face, making it difficult to form areas where the secondary hard phase does not exist. In addition, areas with an increased concentration of the secondary hard phase components are formed.

[0076] Therefore, in the manufacturing of the substrate, the sintering process involves a degreasing process (for example, performed at 600°C), followed by nitrogenization under a nitrogen atmosphere of 1-5 kPa at a heating rate of 3-5°C / min, and 10 -1 It is preferable to hold the sample at 1400 to 1500°C for 60 to 120 minutes under a vacuum atmosphere of Pa or less to decompose the secondary hard phase in the non-substrate ridge regions. After that, it is cooled to room temperature under an inert atmosphere at a cooling rate of 20°C / min or more.

[0077] (2) First layer deposition process The Ti nitride constituting the first layer of this embodiment is manufactured by (a) a carburizing process, (b) a film formation process, and (c) a heat treatment process.

[0078] (a) Carburizing process To achieve an average grain size of 10-20 nm in the interface region, the substrate surface is subjected to a carburizing treatment before the first layer is deposited. Examples of conditions for carburizing treatment include the following: Reaction gas composition (volume %): C2H4: 40.0~60.0%, H2: residual Reaction atmosphere temperature: 900~1000℃ Reaction atmosphere pressure: 5.0~20.0 kPa Reaction time: 60-120 minutes

[0079] (b) Film formation process for the first layer The first layer is deposited using CVD (Chemical Vapor Deposition) to an average thickness of 0.2 to 1.0 μm. Examples of deposition conditions are as follows: Reaction gas composition (volume %): TiCl4: 1.0~5.0%, N2: 15.0~35.0%, H2: remaining Reaction atmosphere temperature: 900~980℃ Reaction atmosphere pressure: 10.0~20.0 kPa

[0080] (c) Heat treatment process Examples of heat treatment conditions for obtaining diffusion layer region A and diffusion layer region B are as follows: Heat treatment temperature: 1100~1150℃ Holding time: 180~240min Heat treatment atmosphere: Vacuum of 0.01 to 0.10 Pa

[0081] (3) Film formation process for the second layer The second layer deposition process, performed after the first layer deposition process, can be carried out using a known CVD method to deposit a coating layer having the desired average composition and average thickness. [Examples]

[0082] Examples will be described. The present invention is not limited to these examples.

[0083] (1) Combination First, as substrate material powders, we prepared WC powder with an average particle size of 2.5 μm, Co powder with an average particle size of 1.5 μm, TiC powder with an average particle size of 1.0 μm, TiN powder with an average particle size of 2.5 μm, NbC powder with an average particle size of 1.0 μm, TaC powder with an average particle size of 1.0 μm, ZrC powder with an average particle size of 0.8 μm, and Cr3C2 powder with an average particle size of 3.0 μm. The average particle size of the raw material powders was measured by the Fischer method.

[0084] (2)Mixing / molding These powders were blended to the composition shown in Table 1, wax was added, and the mixture was attrited in ethanol for 7 hours. After drying under reduced pressure, the mixture was molded at a pressure of 150 MPa to produce compacted powder (compacted powder for producing CNMG120408).

[0085] (3) Sintering Sintering involves degreasing at 600°C. Heating process: Heat at a rate of 4°C / min (20kPa in a nitrogen atmosphere), Holding process: 1450℃ (10 -1 Hold in a vacuum (below Pa) for 90 minutes. Cooling: The system was cooled to room temperature at a cooling rate of 25°C / min under an argon gas atmosphere.

[0086] (4) Processing Subsequently, the substrates A1 to J1 of the examples were fabricated by machining and grinding to the ISO shape CNMG120408.

[0087] (5) Film formation Next, a carburizing process, a film formation process, and a heat treatment process were first carried out on the surface of these substrates under the conditions shown in Table 3, and then a second layer was formed under the conditions shown in Table 5 to obtain the coated tools of the present invention (hereinafter referred to as Examples) 1 to 10 shown in Tables 6 to 8.

[0088] Furthermore, for comparative purposes, comparative substrates A2 to J2 were prepared by mixing, press molding, sintering, and processing in the same manner as in the examples, so as to have the formulations shown in Table 2. By forming a coating layer on the surface under the conditions shown in Tables 4 and 5, comparative example coated tools (hereinafter referred to as comparative examples) 1 to 10 shown in Tables 9 to 11 were manufactured.

[0089] Furthermore, the composition of the substrates, the average grain size of the crystal grains in the interface region, the average thickness of the diffusion layer region A, the diffusion layer region B, and the non-diffusion layer region, and the average composition were determined for each of the Examples 1-10 and Comparative Examples 1-10 using the methods described above. The measurement results are shown in Tables 6-11.

[0090] [Table 1]

[0091] [Table 2]

[0092] [Table 3]

[0093] [Table 4]

[0094] Comparative film formation processes a2 and b2 did not involve a carburizing process, while comparative film formation processes c2 and d2 did not involve a heat treatment process.

[0095] [Table 5]

[0096] [Table 6]

[0097] [Table 7]

[0098] [Table 8]

[0099] [Table 9]

[0100] [Table 10]

[0101] [Table 11]

[0102] Table 6-11 shows that the W content includes unavoidable impurities, and the Ti content also includes unavoidable impurities. Examples 4 and 9 and Comparative Examples 5 and 10 did not have a non-diffusion layer region. Comparative Example 1 also did not have a diffusion layer region.

[0103] Next, for Examples 1-10 and Comparative Examples 1-10, the following wet continuous turning tests (cutting tests A-C) of stainless steel were performed with the tool steel cutter tip clamped with a fixing jig. Then, every minute after the start of the cutting test, the presence or absence of chipping and delamination due to plastic deformation was visually observed, and the flank wear width was measured. When the flank wear width exceeded 0.2 mm, the flank wear width at the time elapsed since the start of the test (measurement time) that exceeded 0.2 mm and the flank wear width at the previous measurement time were linearly approximated to determine the elapsed time from the start of the test that resulted in a flank wear width of 0.2 mm (time until the end of service life). Tables 12-14 show the measurement results for each.

[0104] Cutting test 1 (Results are shown in Table 10) Workpiece material: JIS SUS304 round bar with an outer diameter of 100 mm Cutting speed: 200m / sec Cut: 1.5mm Feed per revolution: 0.3mm Cutting time: 15 minutes

[0105] Cutting test 2 (Results are shown in Table 11) Workpiece material: JIS SUS316 round bar with an outer diameter of 100 mm Cutting speed: 150m / sec Cutting depth: 2.0mm Feed per revolution: 0.2mm Cutting time: 15 minutes

[0106] Cutting test 3 (Results are shown in Table 12) Workpiece material: JIS SUS630 round bar with an outer diameter of 100 mm Cutting speed: 120m / sec Cutting depth: 2.0mm Feed per revolution: 0.15mm Cutting time: 15 minutes

[0107] [Table 12]

[0108] [Table 13]

[0109] [Table 14]

[0110] The results shown in Tables 12-14 demonstrate that Examples 1-10 exhibit excellent chipping resistance and wear resistance in high-speed continuous cutting of stainless steel and other materials. In contrast, Comparative Examples 1 to 10 reached the end of their service life relatively quickly due to peeling of the coating layer and chipping. [Explanation of Symbols]

[0111] 1. Escape 2 Scoop surface 3. Edge of the blade 4. Base ridge section

Claims

1. A surface-coated cutting tool comprising a substrate and a coating layer on the substrate, In the substrate ridge portion and the non-substrate ridge portion of the rest of the substrate, the average composition from the surface of the substrate to 10 μm inward is, respectively, It contains 5.0 to 10.0 mass% Co, 1.0 to 9.0 mass% MA (MA is one or more of Ti and Zr), 0.0 to 0.3 mass% Cr, 5.5 to 6.5 mass% C, 0.1 to 0.6 mass% N, and 2.0 to 6.0 mass% MB (one or more of Nb and Ta), The remainder consists of W and unavoidable impurities. It contains 9.0 to 18.0 mass% Co, 0.0 to 1.0 mass% MC (MC is one or more of Ti and Zr), 0.0 to 0.3 mass% Cr, 5.5 to 6.5 mass% C, 0.0 to 0.1 mass% N, and 0.0 to 1.0 mass% MD (one or more of Nb and Ta), The remainder consists of W and unavoidable impurities. In both the substrate ridge portion and the non-substrate ridge portion, the average composition of the region exceeding 10 μm from the surface of the substrate toward its interior is: It contains 5.0 to 10.0 mass% Co, 1.0 to 9.0 mass% ME (ME is one or more of Ti and Zr), 0.0 to 0.3 mass% Cr, 5.5 to 6.5 mass% C, 0.1 to 0.6 mass% N, and 2.0 to 6.0 mass% MF (MF is one or more of Nb and Ta), The remainder consists of W and unavoidable impurities. The coating layer consists of a first layer in contact with the substrate having an average thickness of 0.2 to 1.0 μm and a second layer in contact with the first layer. The first layer consists of three layer regions: a diffusion layer region A in contact with the substrate ridge, a diffusion layer region B in contact with the non-substrate ridge, and a non-diffusion layer region selectively present on the surfaces of the diffusion layer region A and the diffusion layer region B. The diffusion layer region A and the diffusion layer region B each extend from the interface with the substrate to a depth of 0.1 to 0.2 μm. The non-diffusive layer region A extends from the surface of the diffuse layer region A to contact with the second layer. The non-diffusive layer region B extends from the surface of the diffuse layer region B to contact with the second layer. In both the diffusion layer region A and the diffusion layer region B, the average grain size of the crystal grains from the interface of the substrate to 0.1 μm is 10 to 20 nm. The average composition of the diffusion layer region A is 3.0 to 12.0 atomic percent of W, 3.0 to 12.0 atomic percent of Co, 10.0 to 30.0 atomic percent of C, 0.5 to 3.0 atomic percent of M1 (M1 is one or more of Nb and Ta), 20 to 50 atomic percent of N, and 0.0 to 2.0 atomic percent of M2 (M2 is one or more of Zr and Cr), with the remainder being Ti and unavoidable impurities. The average composition of the diffusion layer region B is 3.0 to 12.0 atomic percent of W, 3.0 to 12.0 atomic percent of Co, 10.0 to 30.0 atomic percent of C, 20 to 50 atomic percent of N, and 0.0 to 0.1 atomic percent of M3 (where M3 is one or more of Nb, Ta, Zr, and Cr), with the remainder being Ti and unavoidable impurities. The average composition of the non-diffusive layer region is 40-60 atomic percent of N, with the remainder being Ti and unavoidable impurities. A surface-coated cutting tool characterized by the following features.

2. The surface-coated cutting tool according to claim 1, characterized in that the second layer is one or more layers made of carbides, nitrides, oxides, carbonites, carbonitrides, or carbonitrides (not limited to stoichiometric composition and including unavoidable impurities) containing one or more elements selected from the group consisting of elements from groups 4 to 6 of the periodic table and Al, and the total average thickness thereof is 3.0 to 20.0 μm.

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