JP6603061B2 - Cermet and cutting tools - Google Patents

Description

  The present invention relates to a cermet and a cutting tool.

  Currently, cermets mainly composed of titanium are widely used as materials for structural members that require wear resistance, slidability, and fracture resistance, such as cutting tools, wear-resistant members, and sliding members. The cermet used for such an application can prolong the lifetime of the cermet member when the reactivity with the counterpart material is low.

  For example, Patent Document 1 discloses boriding the surface of the cemented carbide in order to prevent Co from diffusing from the surface of the cemented carbide.

JP 7-138734 A

  In cermets as well, it has been required to suppress the diffusion of Co into the work material.

The cermet of this embodiment is a cermet containing Ti and W and containing at least one of Co and Ni in a total amount of 8% by mass to 30% by mass,
A hard phase composed of one or more carbonitrides of Group 4, 5, and 6 metals in the periodic table containing Ti and W, and a binder phase containing at least one of Co and Ni and W The bonded phase is a first bonded phase in which the mass ratio of W to the total amount of Co and Ni (W / (Co + Ni)) is 0.8 or less, and the ratio (W / (Co + Ni)) is Including a second bonded phase of 1.2 or more,
After a reaction test in which the FC250 material is brought into contact with the surface of the cermet and a pressure of 130 kPa is applied and the degree of vacuum is 1 Pa and held at 1050 ° C. for 60 minutes, the average diffusion of W into the FC250 material The distance is 30 μm or less.

  The cutting tool of this embodiment uses the cermet as a base.

  According to the cermet of this embodiment, the reactivity with the iron-based metal member is low, the welding of the mating material such as the cutting tool, the wear-resistant member, and the sliding member can be suppressed, and the wear resistance of the cermet is reduced. Can be suppressed.

  According to the cutting tool of this embodiment, since the reactivity with respect to a counterpart material such as a work material can be suppressed, the surface of the cermet is hardly changed during operation such as cutting, and can be used for a long time.

It is a schematic diagram about an example inside the cermet of this embodiment. (A) is an electron beam microanalyzer (EPMA) surface analysis data showing the distribution state of W in the vicinity of the contact surface between the cermet after the reaction test and the FC250 material for an example of the cermet of the present embodiment, (b) Is an EPMA surface analysis data showing the distribution state of W in the vicinity of the contact surface between the cermet and the FC250 material after the reaction test for an example of a conventional cermet, and (c) shows the distribution state of W in (a). It is line analysis data which shows distribution of the average value of the width direction, (d) is line analysis data which shows distribution of the average value of the width direction about the distribution state of W of (c). (A) is EPMA surface analysis data showing the distribution state of Co in the vicinity of the contact surface between the cermet and the FC250 material after the reaction test of FIG. 2 (a), and (b) is the reaction test of FIG. 2 (c). It is EPMA surface analysis data which shows the distribution state of Co about the contact surface vicinity of cermet and FC250 material after, (c) is a line which shows distribution of the average value of the width direction about the distribution state of Co of (a) (D) is line analysis data showing the distribution of the average value in the width direction for the Co distribution state of (c). (A) is EPMA surface analysis data showing the distribution state of Fe in the vicinity of the contact surface between the cermet and the FC250 material after the reaction test of FIG. 2 (a), and (b) is the reaction test of FIG. 2 (c). It is EPMA surface analysis data showing the distribution state of Fe in the vicinity of the contact surface between the later cermet and the FC250 material, and (c) is a line showing the distribution of the average value in the width direction for the distribution state of Fe in (a). It is analysis data, (d) is line analysis data which shows distribution of the average value of the width direction about the distribution state of Fe of (c). (A) is a metallurgical micrograph of the cermet of this embodiment after the reaction test, mirror-polished the cross section of the cermet, etched with Murakami reagent for 1 minute, and observed with a metal microscope, (b) It is the metal micrograph which observed with the metal microscope after etching for 1 minute with the Murakami reagent, after mirror-polishing the cross section of a cermet about the conventional cermet after the reaction test. As for an example of the cermet of this embodiment, (a) is a scanning electron microscope (SEM) photograph of a polished surface including the vicinity of the surface, and (b) is an electron beam micro that shows the distribution state of Co in (a). This is analyzer (EPMA) mapping data, and (c) is EPMA mapping data indicating the distribution state of W for (a).

  An example of the cermet of this embodiment will be described based on a schematic diagram of an example of the inside of the cermet in FIG.

  The cermet 1 of the first embodiment contains Ti and W, and contains at least one of Co and Ni in a total amount of 8% by mass to 30% by mass. Further, the structure of the cermet 1 is composed of a hard phase 2 made of one or more carbonitrides of Group 4, 5, and 6 metals in the periodic table containing at least Ti and W, and at least one of Co and Ni. A binder phase 3 containing W is contained. In microscopic observation of cermet 1, the area ratio of hard phase 2 is 65 to 95 area%, and the area ratio of binder phase 3 is 5 to 35 area%. The area ratio can be calculated from the micrograph of cermet 1 by an image analysis method. In this embodiment, the hard phase 2 has Ti as a main component.

  The binder phase 3 includes a first binder phase 4 having a mass ratio of W to the total amount of Co and Ni (W / (Co + Ni)) of 0.8 or less, and a mass ratio of W to the total amount of Co and Ni (W / (Co + Ni )) Contains the second bonded phase 5 of 1.2 or more. The first bonded phase 4 and the second bonded phase 5 are discriminated based on the result of the ratio of the metal elements at each position by confirming the distribution of each metal element by observing the cermet 1 with a microscope.

Here, a method for specifying the contours of the first bonded phase 4 and the second bonded phase 5 will be described. When there is a constricted portion when the outer shape of the first bonded phase 4 or the second bonded phase 5 is viewed, the shortest length of the constricted portion is assumed as a boundary, and the determination is made as follows. For example, as shown in FIG. 1, when there is a constricted portion when the outer shape of the second bonded phase 5 is viewed, the constricted portion is located in two regions with respect to the shortest length d of the constricted portion. When the longest lengths L ₁ and L _{2 of} the second bonding layer 5 are both three times or more, it is determined that there are two second bonding phases 5 with the constricted portion as a boundary and sandwiching this boundary. On the other hand, if one of the longest lengths of two adjacent areas across the narrowest length of the constricted portion is less than three times, it is determined that the two areas are one without having a boundary. In FIG. 1, the first bonded phases 4, the second bonded phases 5, and the boundary between the first bonded phase 4 and the second bonded phase 5 are indicated by dotted lines.

  Further, the boundary between the first bonded phase 4 and the second bonded phase 5 is specified by confirming the mass ratio of W to the total amount of Co and Ni (W / (Co + Ni)). In addition, there may be other bonded phases that do not belong to any of the first bonded phase 4 and the second bonded phase 5. Even in this case, the boundary between the first bonded phase 4, the second bonded phase 5, and the other bonded phase is specified by confirming the mass ratio of W to the total amount of Co and Ni (W / (Co + Ni)). The micrograph of the cermet 1 is a magnification in which the first binder phase 4 and the second binder phase 5 exist, and the first binder phase 4 and the second binder phase 5 exist in three (three places) or more. Measure with

  The cermet 1 having the first bonded phase 4 and the second bonded phase 5 has high heat dissipation. That is, since the second bonded phase 5 has higher thermal conductivity than the first bonded phase 4, the thermal conductivity in the cermet 1 is increased, and the heat dissipation of the cermet 1 is increased. Therefore, when this cermet 1 is used as a base of a cutting tool, for example, the temperature of the cutting edge is difficult to increase during cutting, and the wear resistance of the cutting edge is improved. Further, the first bonded phase 4 and the second bonded phase 5 are highly elastic with respect to the hard phase 2 in the cermet 1. Therefore, since the second bonded phase 5 has higher elasticity than the composite carbonitride of W and Co, the second bonded phase 5 is elastically deformed and absorbs the impact when the cermet 1 is subjected to an impact. Can do. Therefore, the fracture resistance of the cermet 1 can be increased. Moreover, the 1st binder phase 4 has high wettability with the hard phase 2, can suppress the progress of a crack, and can improve the fracture resistance of the cermet 1 also in this respect.

  The cermet 1 of the present embodiment is a 1050 in a vacuum with a degree of vacuum of 1 Pa in a state in which a pressure of 130 kPa is applied to the surface of the cermet 1 with an FC250 material (hereinafter sometimes abbreviated as FC material) 15 applied. After the reaction test held at 60 ° C. for 60 minutes, the average diffusion distance of W to the FC material 15 is 30 μm or less.

  As a result, when the cermet 1 is used as a structural member that is used in contact with an iron-based member such as the FC material 15, the surface of the cermet 1 is suppressed from being altered, and the cermet 1 is used over a long period of time. can do.

  Here, the average diffusion distance of W to the FC material 15 after the reaction test is measured by the following method. About the laminated body of the cermet 1 and the FC material 15 after the reaction test, a cross section perpendicular to the contact surface between the cermet 1 and the FC material 15 is cut out. About this cross section, W content is measured by the electron beam microanalyzer (EPMA) about the contact surface vicinity of the cermet 1 and the FC material 15 (surface analysis data of Fig.2 (a)). The measurement area in the width direction parallel to the contact surface of the cermet 1 is 150 μm or more, and the average value of the measurement points within this range is measured to obtain the line analysis data in FIG. Although not shown, the W content at a depth of 200 μm to 205 μm from the contact surface of the cermet 1 is measured to obtain an average value, which is taken as the W content inside the cermet 1. Then, the W content in the FC material 15 is measured, and the change rate of the W content within the length of 20 μm in the depth direction is 1% or less with respect to the W content inside the cermet 1. The position (P) is specified, and the distance from the contact surface to P is defined as the W average diffusion distance. That is, the W content in P existing within a depth range of 30 μm from the contact surface of the FC material 15 with the cermet 1, and the W content at a position 20 μm on the opposite side of the contact surface from the point P The difference is 1% of the W content inside the cermet 1. A desirable range of the average diffusion distance of WC to the FC material 15 is 26 μm or less.

  According to the present embodiment, after the reaction test, the W content ratio Ws in the surface portion 10 is less than the depth of 200 μm from the surface of the cermet 1 (hereinafter simply referred to as “inner”. FIGS. The inside 8 is not described.) The ratio (Ws / Wi) of W to the content ratio Wi in 8 is preferably 0.92 or more. As a result, as shown in FIG. 5A, the generation of the η phase 9 in the surface region 7 before the reaction test is suppressed. That is, in the conventional cermet, the movement of the metal element constituting the binder phase is likely to proceed during the reaction test, and the Co ratio is high and the W ratio is likely to be low near the surface. As a result, the η phase 9 is precipitated as shown in FIG. On the other hand, if there is a surface portion 10 in which the ratio (Ws / Wi) is 0.92 or more and the decrease in the abundance ratio of W is small, an increase in the Co ratio in the vicinity of the surface of the cermet 1 and FC Diffusion to the material 15 can be reduced.

  The average diffusion distance of Co to the FC material 15 and the average diffusion distance of Fe to the cermet 1 are also measured in the same manner. 3 shows the distribution of Co content in a cross section perpendicular to the contact surface between cermet 1 and FC material 15 in FIG. 2, and FIG. 4 shows the contact surface between cermet 1 and FC material 15 in FIG. The distribution of Fe content for a vertical cross section is shown. When the average diffusion distance of Co to the FC material 15 is 40 μm or less and when the average diffusion distance of Fe to the cermet 1 is 30 μm or less, the welding resistance on the surface of the cermet 1 is high.

  According to the present embodiment, after the reaction test, the cross section of the cermet 1 is mirror-polished, etched with the Murakami reagent for 1 minute, and observed with a metal microscope, as shown in FIG. It is preferable that the η phase 9 does not exist in the range of 200 μm depth from the surface of 1 or the surface portion 10 in which the abundance ratio of the η phase 9 is 2 area% or less. Thereby, it can suppress that W element diffuses during a reaction test, and can suppress the progress of the alteration of the surface of cermet 1. That is, in the conventional cermet, the abundance ratio of the η phase 9 exists in the surface portion 10 after the reaction test. Since the η phase 9 is lower in hardness than the hard phase 2, if the η9 phase is present in an amount of more than 5% by area, the strength at the surface portion 10 is reduced, and the wear resistance and fracture resistance of the cermet 1 are reduced.

  In the reaction test, for example, the surface with which the FC material 15 of the cermet 1 is contacted may be a baked surface, but it is a surface where a part of the surface region 7 remains after polishing the thickness within 5 μm from the baked surface. It may be a polished surface from which the surface region 7 is removed. The surface roughness of the surface with which the FC material 15 of the cermet 1 is brought into contact is 0.5 μm or less in terms of arithmetic average roughness Ra.

  The ratio of the total area ratio S1 of the first binder phase 4 to the total area ratio S2 of the second binder phase 5 with respect to the total area ratio of the entire binder phase 3 is 0.9 or more. That is, most of the binder phase 3 includes the first binder phase 4 and the second binder phase 5, and the other binder phases may exist with an area ratio of less than 0.1 with respect to the whole binder phase 3. The other binder phase that is not the first binder phase 4 or the second binder phase 5 has a mass ratio of W to the total amount of Co and Ni (W / (Co + Ni)): 0.8 <(W / (Co + Ni)) <1 2 but present between the first bonded phase 4 and the second bonded phase 5 or in the vicinity of the interface with the hard phase 2 of the bonded phase 3 (the first bonded phase 4 or the second bonded phase 5). There is. In addition, in FIG. 1, the structure | tissue in which the other binder phase does not exist is shown.

  In the present embodiment, the total area ratio S1 of the first bonded phase 4 and the total area ratio S2 of the second bonded phase 5 with respect to the total area ratio of the entire bonded phase 3 are within a range of 200 μm depth from the surface of the cermet 1. There is a surface region 7 in which the ratio (S2 / S1) is higher than the ratio (S2 / S1) in the interior 8. As shown in FIG. 6, the Co content decreases, but in the surface region 7, the W content does not decrease as much as the Co content.

Accordingly, when the cermet 1 is used in contact with an iron-based counterpart material, the reactivity with the counterpart material on the surface of the cermet 1 can be further suppressed, and the surface of the cermet 1 can be further prevented from being altered. As a result, the cermet 1 can be used over a long period of time. That is, since the second bonded phase 5 has higher heat resistance than the first bonded phase 4, by increasing the ratio of the second bonded phase 5 on the surface of the cermet 1, the metal element of the cermet 1 when the temperature of the cermet 1 is increased. Diffusion can be suppressed. As a result, alteration on the surface of the cermet 1 can be suppressed. The thickness of the surface region 7 may be the same as the thickness of the surface portion 10 after the reaction test, but is not necessarily the same thickness. The thickness of the surface region 7 is preferably 10 μm to 30 μm.

  In addition, the ratio (S2 / S1) of S2 and S1 in the inside 8 is 0.2 to 1.5. Thereby, both the abrasion resistance and the fracture resistance of the cermet 1 can be enhanced. A particularly desirable range of the ratio (S2 / S1) of S2 and S1 in the interior 8 is 0.3 to 1.2. Here, the total area ratio S1 of the first binder phase 4 is the sum of the area ratios of the first binder phases 4 in the micrograph. Similarly, the total area ratio S <b> 2 of the second bonded phase 5 is the sum of the area ratios of the second bonded phases 5. Similarly, the total area ratio of the entire binder phase 3 is the sum of the area ratios of all the binder phases constituting the binder phase 3.

  The identification of the first bonded phase 4 and the second bonded phase 5 in the surface region 7 is the same as the specified method in the interior 8, and both are within the field of view where the first bonded phase 4 and the second bonded phase 5 coexist. Observe and measure in 3 fields of view.

In this embodiment, the ratio (s2 / s1) between the average area ratio s1 of the first binder phase and the average area ratio s2 of the second binder phase in the interior 8 is 1.1 to 2.0. Thereby, the heat dissipation of the cermet 1 is high, and a compressive stress is generated in the cermet 1, so that the wear resistance and fracture resistance of the cermet 1 can be improved. A particularly desirable range of the ratio (s2 / s1) is 1.2 to 1.7. The average area of each first binder phase in the interior 8 is a 0.04 .mu.m ² ～0.10Myuemu ^2, the average area of each second binder phase in the interior 8 is 0.06μm ² ~0.12μm ^2.

  The average area ratio s1 is an average value of the area ratios of the respective first bonded phases 4 present in the micrograph, and the average area ratio s2 is an average value of the area ratios of the respective second bonded phases 5 present in the micrograph. Yes, it is measured by image analysis.

  Furthermore, in this embodiment, as shown in FIG. 1, when the inside 8 of the cermet 1 is observed with a microscope, the area ratio S1 of the first binder phase 4 in the total area of one field of view is 15 to 22 area%. The area ratio S2 of the second binder phase 5 is 2 to 20 area%, and the sum of S1 and S2 is 17 to 35 area%.

  The hard phase 2 contains a TiCN phase 2a and a solid solution phase 2b made of a composite carbonitride of one or more of Group 4, 5, and 6 metals in the periodic table other than Ti and Ti. With this structure, the toughness of the hard phase 2 is improved, and the fracture resistance can be improved without reducing the wear resistance. In addition, a part thereof may have a cored structure in which a core part made of TiCN phase 2a is surrounded by a peripheral part made of solid solution phase 2b. Further, as a hard phase other than the hard phase 2 seen in FIG. 1, for example, a hard phase not containing Ti, or a hard material composed of one or more carbides or nitrides of Group 4, 5, and 6 metals of the periodic table Although other hard phases such as phases may exist, in the micrograph, the area ratio of the other hard phases to the area ratio of the entire hard phase is 10 area% or less in total. In this embodiment, the EPMA analysis in the SEM observation confirmed the distribution of the metals in Group 4, 5, and 6 in the periodic table, and the group 4, 5, and 6 metals in the periodic table other than Ti and Ti were observed. It is recognized as a solid solution phase 2b made of composite carbonitride.

In the present exemplary state, the average particle diameter da of TiCN phase 2a is 0.05 to 0.5 [mu] m, an average particle diameter _{d b} of the solid solution phase 2b is than the average particle diameter _{d a} of the TiCN phase 2a in 0.5~2μm Is also big. The particle size ratio (d _b / d _a ) is 3.0-10. As a result, the fracture resistance can be improved without reducing the wear resistance of the cermet. The area ratio Sa of the TiCN phase 2a in the micrograph is 20 to 35 area% as an area ratio with respect to the entire visual field, and the area ratio Sb of the solid solution phase 2b is 35 to 50 area% as an area ratio with respect to the entire visual field. Within this range, the fracture resistance can be improved without reducing the wear resistance of the cermet 1.

  The hard phase 2 and the binder phase 3 can be identified by confirming the distribution state and content ratio of each element by an electron beam microanalyzer (EPMA) or Auger analysis. Moreover, the measurement of the particle size of the hard phase 2 is carried out according to the measuring method of the average particle size of the cemented carbide specified in CIS-019D-2005. At this time, the particle diameter of the solid solution phase 2b having a cored structure is calculated by ignoring the presence of the TiCN phase 2a constituting the core part.

  In this embodiment, the carbon content in the cermet 1 is 6.50 mass% to 8.00 mass%. Within this range, both the wear resistance and fracture resistance of the cermet 1 are high. The carbon content in the cermet 1 may have a composition different from that of the interior 8 of the cermet 1 on the surface of the cermet 1, so that a part of the structure polished and removed by 500 μm or more from the surface of the cermet 1 is used as a powder. It can be measured by analysis. A particularly suitable range for the carbon content is 6.50 mass% to 7.00 mass%.

  The nitrogen content in cermet 1 is 6.20% by mass to 7.20% by mass. If it is this range, the abrasion resistance of the cermet 1 is high. The nitrogen content in the cermet 1 can be measured in the same range as the location where the carbon content is analyzed.

  Moreover, in this embodiment, content of each metal element with respect to the total amount of metal elements contained in the cermet 1 is such that Ti is 30% by mass to 55% by mass, W is 10% by mass to 30% by mass, and Nb is 0 to 0%. 20 mass%, Mo 0-10 mass%, Ta 0-10 mass%, V 0-5 mass%, Zr 0-5 mass%, Co 5 mass% -25 mass%, Ni 0-0. It consists of a ratio of 15% by mass. Within this composition range, the cermet 1 has high wear resistance and fracture resistance.

  In particular, when the content ratio of the W element with respect to the total amount of metal elements in the cermet 1 is a ratio of 15% by mass to 30% by mass, the toughness and fracture resistance of the cermet 1 are improved.

  Cermet 1 may further contain a Mn component. This has an effect of suppressing the grain growth of the hard phase 2 and the hardness and strength of the cermet 1 are improved. Part of the Mn component added as a raw material may volatilize during firing, and the Mn content contained in the cermet 1 is less than the content of the Mn component added in the raw material. The Mn content relative to the total amount of metal elements contained in the cermet 1 is 0.01% by mass to 0.5% by mass. When the Mn component is contained more in the second bonded phase 5 than in the hard phase 2 in the cermet 1, there is an effect of suppressing the grain growth of the hard phase 2. The ratio of the Mn content contained in the hard phase 2 to the Mn content contained in the first binder phase 4 is 0.7 to 1.5.

  The cutting tool of the present embodiment is based on the cermet, and the cermet has high heat dissipation, high impact resistance, and high fracture resistance. High fracture resistance. The cutting tool may be one in which the above-described cermet is used as a base and a coating layer such as a TiN layer or a TiAlN layer is provided on the surface thereof.

(Production method)
Next, the manufacturing method of the cermet and cutting tool mentioned above is demonstrated.
First, a TiCN powder having an average particle size of 0.1 to 1.2 μm, particularly 0.3 to 0.9 μm, a WC powder having an average particle size of 0.1 to 2.5 μm, and a periodic table 4 other than TiCN and WC, At least one of group 5, 6 metal carbide powder, nitride powder, carbonitride powder, a predetermined amount of metal Co powder or metal Ni powder having an average particle size of 0.5-5 μm, and an average particle size of 3-15 μm The mixed powder is prepared by adding at least one of the metal W powder and WC _1-x (0 <x ≦ 1) powder to 1 to 20% by mass and optionally adding carbon powder and mixing. Furthermore, a predetermined amount of MnC powder having an average particle size of 0.5 to 5 μm may be added to the mixed powder.

  In this embodiment, TiN powder and WC powder having an average particle size of 0.1 to 3 μm as at least one of carbide powder, nitride powder, and carbonitride powder of periodic tables 4, 5, and 6 metals other than TiCN NbC powder, MoC, TaC powder, VC powder and ZrC powder are applicable.

  The mixed powder is prepared by adding a binder, a solvent, or the like to the raw material powder, and mixing by a known mixing method such as a ball mill, a vibration mill, a jet mill, or an attritor mill. If powder mixing by an attritor mill is used, the raw material powder is pulverized to reduce the particle size, but the metal powder has a high ductility and therefore tends to be difficult to pulverize. Then, a molded body having a predetermined shape is formed from the mixed powder by a known molding method such as press molding, extrusion molding, or injection molding.

Next, according to this embodiment, the said molded object is baked in a vacuum or inert gas atmosphere. According to this embodiment, the cermet having the predetermined structure described above can be produced by firing under the following conditions. As specific firing conditions, (a) the temperature is raised from room temperature to 1100 ° C., and (b) the vacuum is raised from 1100 ° C. to a firing temperature T ₁ of 1330 to 1380 ° C. from 0.1 to 2 ° C./min. The temperature is increased at a temperature rate a, and (c) a temperature increase rate of 4 to 15 ° C./min from a firing temperature T ₁ to a firing temperature T _{2 of} 1500 to 1600 ° C. in vacuum or in an inert gas atmosphere of 30 to 2000 Pa. the temperature was raised at b, (d) was held at sintering temperature _{T 2} 0.5 to 2 hours in an inert gas atmosphere in the vacuum or 30～500Pa, lowering rate of the (e) 5~15 ℃ / min Firing is performed under the firing conditions of e.

By adjusting the average particle diameter of the WC powder and the metal W powder in the raw material powder, and controlling the temperature rising pattern during the firing and the timing of introducing a predetermined amount of inert gas, the Co powder and the Ni powder are It melts while being dissolved in each other, wraps around the hard phase, and bonds between the hard phases. Further, at least one of the metal W powder and the WC _1-x (0 <x ≦ 1) powder that exists in the molded body in a state in which the average particle size is larger than that of the other raw material powder is partially hardened by firing. Although diffused into the phase, some form a second bonded phase. As a result, the cermet 1 having the structure described above can be produced.

That is, if the rate of temperature increase in step (b) is slower than 0.1 ° C./min, the firing time is too long to be practical, and if the rate of temperature increase in step (b) is higher than 2 ° C./min, cermet Voids are likely to occur on the surface of 1. Moreover, when the rate of temperature increase in the step (c) is slower than 4 ° C./min, it is difficult for both the first binder phase and the second binder phase to exist. If the rate of temperature increase in the step (c) is faster than 15 ° C./min, voids are likely to occur on the surface of the cermet 1. When the firing temperature T ₂ is less than 1500 ° C., the sinterability is insufficient, and when the firing temperature T ₂ is higher than 1600 ° C., it is difficult for both the first binder phase and the second binder phase to exist. When the temperature drop rate in the step (e) is slower than 5 ° C./min, particularly when CH ₄ gas is mixed as an inert gas during the steps (c) and (d), the second bonded phase is not formed and W A composite carbonitride containing Co is easily formed. (E) When the temperature-fall rate in a process is faster than 15 degree-C / min, it will become easy to generate | occur | produce a crack on the surface of a cermet. Further, by setting the atmosphere in the step (d) at the time of firing to an inert gas atmosphere of 500 Pa or less, the surface portion 10 having a high abundance ratio of the surface region 7 and W can be easily formed.

  And if desired, a cutting tool is produced by forming a coating layer on the surface of the cermet. A physical vapor deposition (PVD) method such as an ion plating method or a sputtering method can be suitably applied as the coating layer forming method.

TiCN powder having an average particle size of 0.6 μm, WC powder having an average particle size of 1.1 μm, TiN powder having an average particle size of 1.5 μm, TaC powder having an average particle size of 2 μm, an average particle size of 1. 1. 5 μm NbC powder, average particle size 2.0 μm MoC powder, average particle size 1.8 μm ZrC powder, average particle size 1.0 μm VC powder, average particle size 3.0 μm MnC powder, average particle size 4 μm Ni powder, Co powder having an average particle size of 1.9 μm, W powder having an average particle size shown in Table 1, WC _0.5 powder (W powder and WC _0.5 powder are represented by W, WC _{0 in the} table) _.5 ) is mixed at a ratio shown in Table 1 with a stainless steel ball mill and a carbide ball, and wet mixed with isopropyl alcohol (IPA), and 3 mass% of paraffin is added. Mixed. Then, it was press-molded into a cutting tool (slow away tip) shape of CNMG120408 at 150 MPa using the granulated powder granulated by spray drying.

Then, (a) the temperature is increased from room temperature to 1100 ° C., (b) the temperature increase rate a is increased from 1100 ° C. to 1350 ° C. in vacuum at a rate of 0.7 ° C./min, and (c) N _{2 of} 1000 Pa. In a gas atmosphere, the temperature was raised from a firing temperature of 1350 ° C. to a firing temperature T ₂ shown in Table 1 at a heating rate b (described as speed b in Table 1), and (d) N ₂ gas at a pressure shown in Table 1 Firing conditions for holding at a firing temperature T _{2 for} 1 hour in an atmosphere (described as d atmosphere in Table 1) and then lowering the temperature at a temperature decreasing rate e (described as speed e in the table) shown in Table 1. Baked in. Sample No. 18 and 19 were fired in an atmosphere in which a part of N ₂ gas was replaced with CH ₄ gas in the steps (c) and (d).

About the obtained cutting tool, the composition of the metal element contained in the cermet was analyzed by ICP analysis, and the content of each metal element with respect to the total amount of the metal element was calculated. In addition, using a carbon / nitrogen analyzer, the carbon content was measured for a central portion polished from the surface of the cermet by 500 μm or more using a cermet with a known carbon content as a standard sample. The results are shown in Table 2. Sample No. The nitrogen contents in 1 to 13 were all in the range of 6.20% by mass to 7.20% by mass.

  In addition, SEM observation is performed at a position deeper than 200 μm from the surface of the cermet, transmission electron microscope (TEM) observation is performed, the structure of the cermet is confirmed, and an electron beam microanalyzer (EPMA) is used with a 50000 times photograph. The types of the hard phase and the binder phase were specified, and the presence or absence of the TiCN phase, the solid solution phase, the first binder phase, and the second binder phase was confirmed. In addition, about the sample in which the 2nd binder phase exists, the structure | tissue was confirmed in the photograph with the photograph in which the 1st binder phase and the 2nd binder phase each existed in three or more places within a visual field.

  Moreover, it turned out that the cored structure phase exists in the ratio of 10 area% or less with respect to the whole hard phase. Then, image analysis is performed in a 2500 nm × 2000 nm region using commercially available image analysis software, and the average area ratio s1 of the first binder phase, the average area ratio s2 of the second binder phase, and the first binder phase in the visual field. The total area ratio S1, the total area ratio S2 of the second binder phase, and the total area ratio of other binder phases (described as “other” in the table) were confirmed, and the ratio s2 / s1 and the ratio S2 / S1 were described. Further, the total area ratio of S1 and S2 with respect to the entire binder phase (described as S1 + S2 ratio in the table) was calculated. For the hard phase, the average particle size (da, db) and ratio db / da of the TiCN phase and the solid solution phase, the area ratio Sa of the TiCN phase in the visual field, and the area ratio Sb of the solid solution phase were measured. The results are shown in Table 3.

  Furthermore, SEM observation is performed at a depth of 200 μm from the surface of the cermet to confirm the presence or absence of the surface region. When the surface region is present, the thickness of the surface region and the first bonded phase within the visual field are observed. The total area ratio S1, the total area ratio S2 of the second binder phase, and the total area ratio of other binder phases (described as “other” in the table) were confirmed, and the ratio S2 / S1 was expressed. Further, the total area ratio of S1 and S2 with respect to the entire binder phase (described as S1 + S2 ratio in the table) was calculated. For the hard phase, the average particle diameters (da, db) and ratios db / da of the TiCN phase and the solid solution phase, the area ratio Sa of the TiCN phase in the visual field, and the area ratio Sb of the solid solution phase were measured. The results are shown in Table 4.

  Further, the surface of the obtained cermet was polished within the range of 5 μm thickness, so that the surface roughness Ra was 0.5 μm. A reaction test was performed in which a pressure of 130 kPa was applied to the FC material and held at 1050 ° C. for 60 minutes in a vacuum with a degree of vacuum of 1 Pa. After the reaction test, the distribution of W, Co, and Fe was confirmed by an electron beam microanalyzer (EPMA) on the cross section including the interface with the cermet FC material. Furthermore, while confirming the W content ratio in the region where the depth from the surface of the cermet is 200 μm to 205 μm, the average value Wi is calculated, and the content ratio of W in the depth region from the surface of the cermet to 5 μm is confirmed. The average value Ws was calculated and shown in Table 5 as Ws / Wi. Further, the cross section including the interface with the cermet FC material was etched with Murakami reagent for 1 minute and observed with a metal microscope at 400 times, and the presence or absence of an abnormal phase in the surface part from the surface of the cermet to 200 μm was confirmed. confirmed. When the composition of the abnormal phase was confirmed by EPMA, it was found to be an η phase (W, Co carbide phase). Table 5 shows the area ratio of the η phase in the surface portion.

Next, a cutting test was performed under the following cutting conditions using the obtained cutting tool. The results are shown together in Table 5.
(Abrasion resistance test)
Work material: SCM435
Cutting speed: 200 m / min Feed: 0.2 mm / rev
Cutting depth: 2.0mm
Cutting state: wet evaluation method: flank wear width (mm) and cutting edge state (fracture resistance test) at the time of cutting 10 m
Work material: S45C
Cutting speed: 100 m / min Feed: 0.1 to 0.5 mm / rev (+0.05 mm / rev each feed 10 seconds)
Cutting depth: 2.0mm
Cutting condition: Dry evaluation method: Cutting time (seconds) until chipping

  From Tables 1-5, sample no. In Nos. 14 to 19, the second binder phase does not exist, the diffusion distance of W after the reaction test exceeds 30 μm, the flank wear width is large, and the time until loss is fast. It was.

  On the other hand, Sample No., which is a cutting tool comprising a cermet having the structure of the present embodiment, which contains the first binder phase and the second binder phase and the W diffusion distance after the reaction test is 30 μm or less. In Nos. 1 to 13, the flank wear width was small, and the cutting time until chipping was long.

  Especially, sample No. whose content ratio of W element is 15 mass%-30 mass%. In 1 to 11 and 13, the time required to reach the defect became longer. In addition, the sample No. in which the η phase does not exist in the surface portion after the reaction test or exists in a ratio of 2 area% or less. In 1 and 3 to 10, no remarkable welding was observed on the cutting edge in the cutting test. Further, within the range of 200 μm depth from the surface of the cermet, the ratio (S2 / S1) of the total area ratio S1 of the first binder phase to the total area ratio S2 of the second binder phase with respect to the total area ratio of the whole binder phase is (S2 / S1). Sample No. 2 having a surface area higher than the ratio (S2 / S1) inside the cermet from the depth of 200 μm. In 1, 3, 10 and 12, the flank wear width was small.

  Furthermore, after the reaction test, when the surface obtained by etching the cermet cross section is observed with a metallographic microscope, the η phase is not present in the region 200 μm deep from the surface of the cermet, or the abundance ratio of the η phase is 2 Sample No. having a surface portion existing in a range of area% or less. In Nos. 1, 3 to 10, welding on the cutting edge was reduced. In addition, the sample No. 2 in which the ratio (Ws / Wi) of the W content ratio Ws in the surface portion to the W content ratio Wi in the interior is 0.92 or more. In 1, 3 to 10, the flank wear width was further reduced.

DESCRIPTION OF SYMBOLS 1 Cermet 2 Hard phase 2a TiCN phase 2b Solid solution phase 3 Bonded phase 4 1st bonded phase 5 2nd bonded phase 7 Surface region 8 Internal 10 Surface part 15 FC material (FC250 material)

Claims (6)

A cermet containing Ti and W and containing at least one of Co and Ni in a total amount of 8% by mass to 30% by mass,
A hard phase composed of one or more carbonitrides of Group 4, 5, and 6 metals in the periodic table containing Ti and W, and a binder phase containing at least one of Co and Ni and W The bonded phase is a first bonded phase in which the mass ratio of W to the total amount of Co and Ni (W / (Co + Ni)) is 0.8 or less, and the ratio (W / (Co + Ni)) is Including a second bonded phase of 1.2 or more,
After a reaction test in which the FC250 material is brought into contact with the surface of the cermet and a pressure of 130 kPa is applied and the degree of vacuum is 1 Pa and held at 1050 ° C. for 60 minutes, the average diffusion of W into the FC250 material Cermet with a distance of 30 μm or less. The cermet according to claim 1, wherein the content ratio of the W element to the total amount of metal elements in the cermet is a ratio of 15 mass% to 30 mass%.   The ratio of the total area ratio S1 of the first binder phase to the total area ratio S2 of the second binder phase to the total area ratio of the whole binder phase (S2 / S1) within a range of 200 μm depth from the surface of the cermet. 3 is a cermet having a surface area higher than the ratio (S2 / S1) in the interior of the cermet from a depth of 200 μm from the surface of the cermet. After the reaction test, when the surface obtained by etching the cross section of the cermet is observed with a metallographic microscope, the η phase is not present in the region having a depth of 200 μm from the surface of the cermet or the presence of the η phase. The cermet according to any one of claims 1 to 3, wherein the cermet has a surface portion that is present in a ratio of 2 area% or less. A content ratio Ws of W in the surface portion, the ratio between the content ratio Wi of W inside than said surface surface (Ws / Wi) cermet according to claim 4 is 0.92 or more.   A cutting tool comprising the cermet according to claim 1 as a base.