Cutting tool made of cermet

Abstract

This cutting tool made of cermet is characterized by comprising a hard phase, a binder phase, and a carbonitride phase, wherein: the hard phase contains TiCN and TiMCN (M is at least one element selected from the group consisting of Zr, Hf, V, Nb, Ta, Cr, Mo, and W) as a main component; the binder phase contains Co as a main component; and the carbonitride phase is dispersed within the binder phase and contains a carbonitride of the element M as a main component.

Description

Cermet cutting tools

[0001] This invention relates to a cermet cutting tool. This application claims priority to Japanese Patent Application No. 2024-54387, filed on March 28, 2024. The entire contents of said Japanese patent application are incorporated herein by reference.

[0002] Although cermet cutting tools have insufficient wear resistance compared to cutting tools made of cemented carbide, they are used for finish cutting because they are less likely to weld to the workpiece. Various proposals have been made to improve the wear resistance and other properties of cermet cutting tools.

[0003] For example, Patent Document 1 describes a cermet cutting tool that contains TiCN as an essential component, 50 to 95 mass % of a hard phase mainly composed of carbides, nitrides, carbonitrides of Ti, and one or more carbides, nitrides, or carbonitrides of elements in Groups 4 to 6 of the periodic table, with the remainder being an iron-group metal as a binder phase, and that is provided with η-phase carbides whose maximum X-ray diffraction intensity is in the range of 2 to 30, where the maximum X-ray diffraction intensity of the TiCN is taken as 100. The cermet cutting tool is said to be capable of cutting in wet cutting regions where conventional cermet cutting tools were not applicable.

[0004] Furthermore, for example, Patent Document 2 describes a cermet cutting tool in which a binder phase mainly composed of Co contains composite carbide phases of W and Co, each having a hexagonal crystal structure and a cubic crystal structure, at a predetermined ratio. The cermet cutting tool is said to exhibit excellent resistance to plastic deformation, thermal shock, chipping, and wear resistance even when used in high-speed cutting.

[0005] JP 2000-135606 A JP 2009-154224 A

[0006] The present invention has been made in consideration of the above circumstances and proposals, and has an object to provide a cermet cutting tool having excellent wear resistance in high-speed cutting of low alloy steel and the like.

[0007] A cermet cutting tool according to an embodiment of the present invention comprises a hard phase, a binder phase, and a carbonitride phase, wherein the hard phase is primarily composed of TiCN and TiMCN (M is at least one element selected from the group consisting of Zr, Hf, V, Nb, Ta, Cr, Mo, and W), the binder phase is primarily composed of Co, and the carbonitride phase is scattered within the binder phase and is primarily composed of a carbonitride of element M.

[0008] The cermet cutting tool according to the above embodiment may satisfy one or more of the following (1) to (3).

[0009] (1) The area of ​​the carbonitride phase is 0.2 to 10.0% of the sum of the areas of the binder phase and the carbonitride phase. (2) When the N content of the entire cutting tool is [N] atomic %, and the C content is [C] atomic %, [N] / ([C] + [N]) is 0.30 to 0.70. (3) The carbonitride phase has an average equivalent circle diameter (D50) of 50 to 120 nm.

[0010] The cermet cutting tool has excellent wear resistance even when used in high-speed cutting of low-alloy steel and the like.

[0011] 1 is an example of a schematic diagram of the structure of a cermet cutting tool according to an embodiment of the present invention, and FIG. 2 is an example of a graph (schematic diagram) showing a normalized frequency distribution of the brightness of each pixel in 256 gradations obtained by observing the structure of the cermet cutting tool according to an embodiment of the present invention with an SEM.

[0012] The present inventors have conducted extensive research into ways to obtain excellent wear resistance for cermet cutting tools even in high-temperature environments brought about by high-efficiency cutting, including high-speed cutting at cutting speeds of 200 m / min or more, for low-alloy steels, etc. As a result, they have recognized that even if an η phase or a W-Co carbide phase is present in a cermet cutting tool, these phases do not exist stably in the high-temperature environment, and therefore the cermet cutting tool cannot obtain sufficient wear resistance.

[0013] Therefore, the inventors conducted further studies and found that when a carbonitride phase containing an element of Groups 4, 5, and 6 of the periodic table excluding Ti is present in a cermet cutting tool, the cermet cutting tool can obtain sufficient wear resistance even in the above-mentioned high-temperature environment. The present invention is based on this finding.

[0014] Cermet cutting tools according to embodiments of the present invention will be described in more detail below. In this specification and claims, when a numerical range is expressed using "L to M" (where L and M are both numerical values), the range includes an upper limit (M) and a lower limit (L), and when a unit is specified for only the upper limit (M), the unit for the lower limit (L) is the same as that for the upper limit (M). Unless otherwise specified, "average" refers to the arithmetic mean.

[0015] As shown in FIG. 1 , the structure of one embodiment of the cermet cutting tool of the present invention includes a hard phase (1), a binder phase (2), and a carbonitride phase (3). The carbonitride phase (3) is scattered within the binder phase (2), but as described below, some carbonitride phases may not be scattered within the binder phase (2) as long as they are present in a predetermined number ratio or less. As described below, the hard phase (1) contains TiCN (4) and TiMCN (5), which exhibit differences in shading when observed under a microscope. In the claims and the specification, the term "major component" means that the component referred to as the "major component" in the phase accounts for 50% by mass or more. For example, this means that the total of TiCN (4) and TiMCN (5) in the hard phase is 50% by mass or more.

[0016] 1. Structure and composition: As mentioned above, cermet cutting tools have a hard phase, a binder phase, and a carbonitride phase. While cermet cutting tools are manufactured so that no phases other than the hard phase, binder phase, and carbonitride phase are present, unintended phases such as voids, free carbon phases, and intermetallic compound phases may be present. These phases are collectively referred to as the X phase.

[0017] (1) Hard Phase The hard phase contains TiCN and TiMCN as its main components (M is one or more of elements from Groups 4, 5, and 6 of the periodic table excluding Ti (i.e., Zr, Hf, V, Nb, Ta, Cr, Mo, and W)). Addition of M to TiCN improves the stability of the hard phase in high-temperature environments. Ignoring trace amounts of other components (for example, components of the binder phase contained by diffusion and unavoidable impurities), the hard phase can be considered to consist of TiCN and TiMCN.

[0018] The average composition of TiCN and TiMCN is as follows: TiCN is TiMCN; ｘ N １－ｘ , where 0.0<x<1.0, and TiMCN is Ti ｙ M １－ｙ C ｚ N １－ｚ However, 0.0<y<1.0 and 0.0<z<1.0. It is more preferable that the ranges of x, y, and z are 0.4<x<0.7, 0.6<y<0.9, and 0.4<z<0.7, respectively.

[0019] Here, M is at least one element selected from the group consisting of elements of Groups 4, 5, and 6 of the periodic table excluding Ti (i.e., Zr, Hf, V, Nb, Ta, Cr, Mo, and W), and among these, at least one element selected from the group consisting of Zr, Nb, Cr, Mo, and W is preferred. This is because the carbonitride phase in contact with the binder phase, which will be described later, increases the strength and hardness of the cermet cutting tool, thereby improving its wear resistance, and in order to improve this wear resistance, it is preferred that M be at least one element described here.

[0020] The average equivalent circle diameter (D50: median diameter at 50% of the area ratio) of the hard phase is more preferably 700 to 1500 nm, at which point the above-mentioned object can be more reliably achieved. The area occupied by the hard phase is preferably 80 to 95% by area, the reason for which will be described later. This area is determined by observing an arbitrary region on the surface or cross section of the cermet cutting tool, and the details will be described later.

[0021] The area ratio of each of TiCN and TiMCN contained in the hard phase is more preferably (area of ​​TiCN) / (area of ​​TiMCN)×100=50.0 to 60.0%. If this area ratio is satisfied, the above-mentioned object can be achieved more reliably.

[0022] (2) Binder Phase The binder phase is a phase containing Co as a main component, and may further contain one or more of Ni and Fe in addition to Co. The binder phase may also contain components that constitute the hard phase and carbonitride phase, and unavoidable impurities.

[0023] The area occupied by the binder phase is more preferably 5.0 to 17.0% of the area occupied by the hard phase, as calculated by (area occupied by binder phase) / (area occupied by hard phase)×100. However, this preferred range is premised on the fact that the ratio of the area occupied by the carbonitride phase to the sum of the area occupied by the binder phase and the area occupied by the carbonitride phase satisfies the range described below.

[0024] (3) Carbonitride Phase The carbonitride phase is scattered throughout the binder phase and preferably contains, as a main component, at least one carbonitride (not limited to a stoichiometric composition) of element M contained in TiMCN in the hard phase. This carbonitride phase provides the cermet cutting tool with sufficient wear resistance in the high-temperature environment during cutting. The carbonitride phase may or may not be in contact with the hard phase.

[0025] The carbonitride phase preferably has an average equivalent circle diameter (D50: defined the same as that of the hard phase) of 50 to 120 nm. When the average equivalent circle diameter is in this range, the above-mentioned object can be more reliably achieved.

[0026] It is more preferable that the ratio of the area occupied by the carbonitride phase to the sum of the area occupied by the binder phase and the area occupied by the carbonitride phase, i.e., (area occupied by the carbonitride phase) / (sum of the area occupied by the binder phase and the area occupied by the carbonitride phase) x 100, is 0.2 to 10.0%. By satisfying this range, the cermet cutting tool can be surely provided with wear resistance.

[0027] When the area occupied by the hard phase is 80 to 95 area % and the above-mentioned (area occupied by the carbonitride phase) / (sum of the area occupied by the binder phase and the area occupied by the carbonitride phase)×100 is 0.2 to 10.0%, the cermet cutting tool is more reliably provided with wear resistance.

[0028] (4) N and C Contents of the Entire Cutting Tool When the N content of the entire cermet cutting tool (excluding the coating layer, if any) is [N] atomic %, and the C content is [C] atomic %, the N content ratio, defined as [N] / ([C] + [N]), is more preferably 0.30 to 0.70. The reason why this range of N content ratio is more preferable is that if it is less than 0.30, wear may occur at the infeed boundary of the cutting edge, i.e., tool damage may develop locally at the boundary between the surface where the tool is cutting into the workpiece and the surface where it is not cutting into the workpiece. If it exceeds 0.70, the cutting tool may become porous, reducing the strength of the cutting edge, making chipping more likely to occur during cutting, and preventing stable cutting performance. Wear at the infeed boundary of the cutting edge can be evaluated by the flank wear width.

[0029] (5) Inevitable Impurities The hard phase, binder phase and carbonitride phase may contain impurities that are unintentionally mixed in during the manufacturing process, that is, unavoidable impurities.

[0030] 2. Measurement method 2-1. Observation field An arbitrary surface or cross section of the cermet cutting tool is polished to set an observation field. The observation field can be, for example, one or more rectangular measurement areas measuring 16 μm in length and 12 μm in width set at arbitrary positions. This observation field is observed using a scanning electron microscope (SEM) and an energy dispersive X-ray spectrometer (EDS) attached to the SEM.

[0031] 2-2. Identification of Each Phase Identification of each phase is performed using a scanning electron microscope (SEM) and an energy dispersive X-ray spectrometer (EDS) attached to the SEM. A cross section of a cermet cutting tool is mirror-polished to a smooth surface for SEM and EDS observation. An observation field (e.g., one or more rectangles measuring 16 μm in length and 12 μm in width) is set for the mirror-polished cross section, and the section is observed using the SEM. The observed image is processed as a grayscale image with 256 levels, and the frequency distribution of pixels corresponding to each level is obtained. A graph is then created with brightness on the horizontal axis, black as the origin (0), white as the scale of 255, and the vertical axis as normalized frequency, resulting in a brightness frequency distribution with two frequency peaks. This frequency distribution is used to identify the phases by setting thresholds as follows: Note that the normalized frequency is defined as the maximum frequency in the entire brightness frequency distribution, with 100 being the maximum frequency. Here, the spacing between pixels can be, for example, 30 nm in both the vertical and horizontal directions. The number of pixels from which the frequency distribution is obtained is 150,000 to 250,000. The following explanation will be made with reference to Figure 2 (a graph showing the frequency distribution normalized for the luminance of each pixel).

[0032] 1) Identification of the phase considered to be the hard phase TiCN All pixels between the pixel with the brightness observed to be closest to black (taking a frequency greater than 0) and the pixel at the midpoint between the two peaks in the frequency distribution (referred to as left-side threshold A) are considered to be pixels belonging to the hard phase TiCN. Just to be sure, EDS analysis is performed at each position of these pixels to confirm that each pixel satisfies the composition of the TiCN phase, that is, contains 50 mass% or more of TiCN.

[0033] 2) Identification of the phase considered to be the hard phase TiMCN All pixels between the pixel having a brightness located immediately to the right of the left threshold A and the pixel located at an intermediate position (referred to as right threshold C) between a predetermined whiter brightness B are considered to belong to the hard phase TiMCN. Here, the predetermined whiter brightness B refers to the brightness of the pixel having the smallest frequency exceeding 0 (which may be less than 1) relative to the maximum normalized frequency (100), starting from the brightness closest to white. Just to be sure, EDS analysis is performed at each position of these pixels to confirm that each pixel satisfies the composition of the TiMCN phase, that is, that it contains 50 mass % or more of TiMCN.

[0034] 3) Identification of the phase to be regarded as the binder phase All pixels between the brightness located immediately to the right of the right threshold C and brightness B are regarded as belonging to the binder phase. To be sure, EDS analysis is performed at each position of these pixels to confirm whether each pixel satisfies the composition of the binder phase, that is, whether it contains 50 mass % or more of Co.

[0035] 4) Identification of phases to be treated as carbonitride phases Pixels with a brightness value greater than brightness B (pixels with the whitest brightness have a frequency greater than 0) are considered to belong to the carbonitride phase. Just to be sure, EDS analysis is performed at each position of these pixels to confirm whether each pixel satisfies the composition of the carbonitride phase, that is, whether the total of one or more types of carbonitrides among the M contained in TiMCN is 50 mass% or more.

[0036] As already mentioned, the region that does not fall into any of the hard phase, binder phase, and carbonitride phase is regarded as the X phase. When produced by the method exemplified in this specification, which will be described later, the area ratio of the X phase is less than 1%, and the influence of the X phase on the wear resistance and fracture resistance when the cermet of this embodiment is used as a cutting tool is negligible, so no further mention will be made.

[0037] 2-3. Areas of hard phase, binder phase, and carbonitride phase, and average equivalent circle diameter (D50) of carbonitride phase Based on the hard phase, binder phase, and carbonitride phase identified above, the area of ​​each is determined using image processing software, and the average equivalent circle diameter is calculated. That is, the area is calculated from the area ratio, which is the ratio of the number of pixels belonging to each phase to the total number of pixels in the observation field, and the average equivalent circle diameter is calculated from this area. In addition, the areas of TiCN and TiMCN in the hard phase are also measured using image processing software in the same way, and their area ratios are calculated.

[0038] Here, when determining the area, area ratio, and average diameter (D50) of carbonitrides, the hard phase, binder phase, and carbonitride phase for which the average particle size is measured are each set to 1000 or more, and the number of observation fields is increased as described above until the number reaches 1000 or more. Then, the diameter of a circle equal to the area of ​​one hard phase or carbonitride phase is taken as the particle size, and a graph is drawn in which the horizontal axis represents this particle size and the vertical axis represents the integrated percentage of the area based on the cumulative value of the area relative to the particle size, and the particle size when the integrated percentage reaches 50% is taken as the average circle-equivalent diameter (D50: median diameter).

[0039] The N content ratio ([N] / ([C]+[N])) is determined by cutting out a cermet cutting tool with a mass of 3 to 4 g from the inside of the tool (a region 600 μm or more deep from the surface) using a precision cutting machine or grinding machine, pulverizing the cut-out, and measuring the C and N contents using a combustion method to calculate [N] / ([C]+[N]).

[0040] 2-5. Confirmation that the carbonitride phase is in contact with the binder phase The carbonitride phase being in contact with the binder phase does not mean that all of the carbonitride phase is in contact with the binder phase, but means that if the number ratio is 10% or less (or 0%), the carbonitride phase is not in contact with the binder phase at all, and some of the carbonitride phase may exist in the hard phase. The above-mentioned measurement area is observed with an SEM at a magnification of 10,000 times, and a total of 1,000 or more carbonitride phases are observed (increasing the measurement area of ​​the same size until 1,000 or more carbonitride phases can be observed), and if it can be confirmed that even a part of the interface is in contact with the binder phase, it is determined that the carbonitride phase is in contact with the binder phase.

[0041] 3. Manufacturing Method The cermet sintered body of this embodiment can be manufactured, for example, by the following process. After blending the raw material powders to a predetermined composition, wax is added, the mixture is packed into an attritor, wet-mixed in alcohol, dried, and press-molded to obtain a green body. This green body is then sintered. As a rule, the heating step before sintering in a nitrogen atmosphere (preferably at a sintering temperature of 1400-1490°C) is performed in a vacuum atmosphere. However, it is preferable to include a temperature range (e.g., 1100-1200°C) in the heating step before sintering, followed by heating in a vacuum atmosphere and subsequent heating to a temperature below the sintering temperature in a nitrogen atmosphere, followed by holding at this temperature for a predetermined time (20-40 minutes) in a nitrogen atmosphere. This reduces the amount of M dissolved in the binder phase, resulting in the formation of a carbonitride phase containing M within the binder phase. After sintering, the green body is cooled and then machined as a post-processing step.

[0042] 4. Coating Layer The surface of the cermet cutting tool may be provided with a coating layer consisting of one or more layers formed by a known film-forming method and having a total average thickness of 0.1 to 20.0 μm. The provision of the coating layer further improves the wear resistance, etc. of the cermet cutting tool due to the wear resistance, etc. imparted by the coating layer.

[0043] Here, the type of coating layer is not particularly limited, but examples include one or more of a Ti carbonitride layer, nitride layer, carbonitride layer, carbonate layer, and carbonitride oxide layer, a Ti-Al composite nitride layer, a composite carbonitride layer, and an aluminum oxide layer. These layers may be formed alone or in combination. Note that the composition of each of the above-mentioned layers is not limited to a stoichiometric composition.

[0044] The above description includes the following supplementary notes: (Supplementary Note 1) A cermet cutting tool comprising a hard phase, a binder phase, and a carbonitride phase, wherein the hard phase contains TiCN and TiMCN (M is at least one element selected from the group consisting of Zr, Hf, V, Nb, Ta, Cr, Mo, and W) as main components, the binder phase contains Co as a main component, and the carbonitride phase is scattered throughout the binder phase and contains a carbonitride of the element M as a main component. (Supplementary Note 2) The cermet cutting tool according to Supplementary Note 1, wherein M is at least one element selected from Zr, Nb, Cr, Mo, and W. (Appendix 3) The cermet cutting tool according to Appendices 1 or 2, characterized in that the ratio of the area of ​​the carbonitride phase to the sum of the area of ​​the binder phase and the area of ​​the carbonitride phase is 0.2 to 10.0%. (Appendix 4) The cermet cutting tool according to any of Appendices 1 to 3, characterized in that, when the N content of the entire cutting tool is [N] and the C content is [C], [N] / ([C]+[N]) is 0.30 to 0.70. (Appendix 5) The cermet cutting tool according to any of Appendices 1 to 4, characterized in that the carbonitride phase has an average equivalent circle diameter (D50) of 50 to 120 nm. (Appendix 6) The cermet cutting tool according to any of Appendices 1 to 5, characterized in that the area of ​​the hard phase is 80 to 95 area%. (Appendix 7) The cermet cutting tool according to any one of Appendices 1 to 6, characterized in that the ratio of the area occupied by the binder phase to the area of ​​the hard phase is 5.0 to 17.0. (Appendix 8) The cermet cutting tool according to any one of Appendices 1 to 7, characterized in that the areas occupied by the TiCN and TiMCN in the hard phase respectively are, in area ratio, (area of ​​TiCN) / (area of ​​TiMCN)×100=50.0 to 60.0%. (Appendix 9) The cermet cutting tool according to any one of Appendices 1 to 7, characterized in that the area occupied by the TiCN and TiMCN in the hard phase respectively is, in area ratio, (area of ​​TiCN) / (area of ​​TiMCN)×100=50.0 to 60.0%. ｘ N １－ｘ , TiMCN is represented by the formula: Ti ｙ M １－ｙ C ｚ N １－ｚwherein the ranges of x, y, and z are 0.4<x<0.7, 0.6<y<0.9, and 0.4<z<0.7, respectively.

[0045] Next, the cermet cutting tool of the present invention will be specifically described by way of an example in which it is applied to an insert, but the present invention is not limited to the example in any way.

[0046] Powders having particle sizes shown in Table 1 were used as raw material powders. These raw material powders were blended as shown in Table 2, and then wax was added and the mixture was filled into an attritor. Cermet balls were added as a mixing medium, and wet mixing was carried out in alcohol for 11 hours, followed by drying. The blended composition was then press-molded into a green compact to obtain a green compact. The particle sizes shown in Table 1 are Fischer diameters.

[0047] Next, the produced green compact was sintered and honed to produce Example Tools 1 to 7 and Comparative Example Tools 1' to 3' shown in Table 3, each having an insert shape of CNMG120408-FH. Example Tools 1 to 7 and Comparative Example Tools 1' to 3' were produced using the same manufacturing process, with only the sintering conditions being different.

[0048] The sintering of Example Tools 1 to 7 was performed in the following steps (A) to (H). (A) The tool was heated from 200 to 600°C at a temperature increase rate of 4°C / min, followed by degreasing. (B) The tool was heated from 600 to 1100°C at a temperature increase rate of 4°C / min in a vacuum atmosphere with a pressure of 20 Pa or less. (C) The tool was heated from 1100 to 1200°C at a temperature increase rate of 4°C / min in a nitrogen atmosphere under a reduced pressure of 500 Pa. (D) The tool was heated from 1200 to 1300°C at a temperature increase rate of 1.5°C / min in a vacuum atmosphere with a pressure of 20 Pa or less. (E) The tool was heated from 1300 to 1400°C at a temperature increase rate of 1.5°C / min in a nitrogen atmosphere under a reduced pressure of 100 Pa, and held at that temperature for 30 minutes. (F) The sample was heated from 1400°C to 1490°C at a temperature increase rate of 1.5°C / min in a nitrogen atmosphere under reduced pressure of 100 Pa, and then held at that temperature for 3 hours and 30 minutes. (G) The sample was cooled from 1490°C to 1300°C at a cooling rate of 5°C / min in an argon atmosphere at 100 Pa. (H) Heating was stopped, and argon gas was introduced into the furnace at a pressure of 20 kPa to cool the sample to room temperature.

[0049] The sintering conditions for Comparative Example Tools 1' to 3' shown in Table 3 were as follows: (A') Degreasing was performed by heating from 200°C to 800°C at a temperature increase rate of 4°C / min. (B') Heating from 800°C to 1400°C at a temperature increase rate of 4°C / min in a vacuum atmosphere of 20 Pa or less. (C') Heating from 1400°C to 1500°C at a temperature increase rate of 1.5°C / min in a nitrogen atmosphere under reduced pressure of 100 Pa, and maintaining this temperature in the atmosphere for 1 hour. (D') Cooling to room temperature in a furnace.

[0050]

[0051]

[0052]

[0053] In Table 3, "x" represents TiC ｘ N １－ｘ , and "y, z" are the values ​​of x in Ti ｙ M １－ｙ C ｚ N １－ｚThe values ​​of y and z are shown in Table 1, and "◯" indicates that one or more carbonitrides of M (described as M in TiMCN) contained as hard phase components are contained in the carbonitride phase as the main component, and "-" indicates that there is no applicable component.

[0054] The values ​​in Table 3 were determined by the above-mentioned measurement method, and the software used for image processing was Image J (version 1.53k) distributed by the NIH in the United States.

[0055] Next, the thus obtained Example Tools 1 to 7 and Comparative Tools 1' to 3' were subjected to the following cutting test to evaluate their machining performance.

[0056] Cutting test: Continuous cutting test Workpiece: SNCM439 Cutting speed: 300 m / min. Depth of cut: 0.5 mm Feed: 0.1 mm / rev.

[0057] After the cutting test started, the flank wear width and boundary wear amount were measured every 5 minutes. The flank wear width after 20 minutes was measured is shown in Table 4. The time (minutes) to reach the end of life in Table 4 is as follows. The cutting test was continued even after 20 minutes had passed, and the flank wear width and boundary wear amount were still measured. The cutting test was then terminated at the measurement time (time from the start of the cutting test) when either the flank wear width or the boundary wear amount first reached 0.20 mm or more.

[0058] If, at the end of the cutting test, either the flank wear width or the boundary wear amount was exactly 0.20 mm and the other was less than 0.20 mm, or if both the flank wear width and the boundary wear amount were exactly 0.20 mm, this measurement time was defined as the time to end of life. If, at this measurement time, either the flank wear width or the boundary wear amount exceeded 0.20 mm and the other was 0.20 mm or less, a linear approximation was made between the flank wear width or the boundary wear amount at the measurement time immediately preceding this measurement and the flank wear width or the boundary wear amount at this measurement time (connected by a straight line), and the time at which the one exceeding 0.20 mm became exactly 0.20 mm was calculated and defined as the time to end of life. When both the flank wear width and boundary wear amount exceeded 0.20 mm, a linear approximation was performed between the flank wear width and boundary wear amount at the measurement time immediately preceding this measurement and the flank wear width and boundary wear amount at this measurement time, the time at which they reached exactly 0.20 mm was calculated, and the calculated time at which the flank wear width or boundary wear amount reached exactly 0.20 mm earlier was taken as the time to reach the end of life.

[0059]

[0060] As is clear from Table 4, all of the example tools had small flank wear widths, long life spans, and were therefore durable. On the other hand, all of the comparative example tools had large flank wear widths and reached the end of their life in short periods.

[0061] The above-disclosed embodiments are merely illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, not by the above-disclosed embodiments, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0062] 1 Hard phase 2 Binding phase 3 Carbonitride phase 4 Hard phase (TiCN) 5 Hard phase (TiMCN)

Claims

1. A cermet cutting tool comprising a hard phase, a binder phase, and a carbonitride phase, wherein the hard phase contains TiCN and TiMCN (wherein M is at least one element selected from the group consisting of Zr, Hf, V, Nb, Ta, Cr, Mo, and W) as its main components, the binder phase contains Co as its main component, and the carbonitride phase is scattered within the binder phase and contains a carbonitride of element M as its main component.

2. A cermet cutting tool according to claim 1, characterized in that the ratio of the area of ​​the carbonitride phase to the sum of the area of ​​the binder phase and the area of ​​the carbonitride phase is 0.2 to 10.0%.

3. A cermet cutting tool according to claim 1 or 2, characterized in that, when the N content of the entire cutting tool is [N] and the C content is [C], the ratio [N] / ([C]+[N]) is 0.30 to 0.

70.

4. A cermet cutting tool according to claim 1 or 2, characterized in that the carbonitride phase has an average equivalent circle diameter (D50) of 50 to 120 nm.

Images