JP2023095013A - Cermet compact - Google Patents

Abstract

To provide a cermet compact excellent in defect resistance, excellent also in wear resistance and resistance to plastic deformation, and capable of extending a tool life.SOLUTION: A cermet compact containing a hard phase and a binder phase, wherein the hard phase is a phase containing a carbonitride, carbide or nitride containing a specific component, the binder phase is a phase containing a specific component, and a hard phase content is 82 mass% or more and 93 mass% or less, the binder phase content is 7 mass% or more and 18 mass% or less, and the hard phase (i) contains the first hard phase and second hard phase having a cubic crystal structure exhibiting a specific diffraction peak in XRD measurement, wherein the residual stress of the second hard phase is -1000 MPa or more and -600 MPa or less, and the residual stress of the binder phase is -600 MPa or more and -200 MPa or less, wherein the thickness of the first hard phase-rich region is 0 μm or more and 1.0 μm or less, and the surface bonding phase ratio is 0.80 or more and 0.95 or less.SELECTED DRAWING: None

Description

The present invention relates to a cermet sintered body.

Cermet tools are superior to cemented carbide tools in resistance to reaction with iron and high temperature strength. Therefore, cermet tools are often used for finish machining of ferrous materials, etc., taking advantage of such characteristics.

Various cermet-made tools have been proposed so far. , the arithmetic mean roughness Ra at a cut-off value of 0.08 mm exceeds 0.2 μm, while the surface roughness of the insert flank and chip breaker has an arithmetic mean roughness Ra at a cut-off value of 0.08 mm There has been proposed a cutting insert made of titanium carbonitride-based cermet, characterized in that the residual stress of the hard phase on the surface of the insert is 450 MPa or more in compression.

JP 2011-088239 A

In recent years, the demand for high-speed cutting and labor-saving has become more stringent, and along with this, there is a tendency to desire high-speed cutting and heavy cutting such as high feed and high depth of cut. Under such severe high-speed cutting conditions, tool life tends to be shorter than before.

In Patent Document 1, the surface of a cermet tool is subjected to wet blasting to smooth the surface of the tool and at the same time to impart a predetermined compressive residual stress to the surface of the insert, thereby improving the chipping resistance of the tool to some extent. However, it cannot be said that the performance is sufficient. In addition, since the cermet cutting insert described in Patent Document 1 has not been improved in wear resistance and plastic deformation resistance, it is difficult to extend the tool life in high-speed cutting.

The present invention has been made in view of the above circumstances, and provides a cermet sintered body that has excellent chipping resistance, excellent wear resistance and plastic deformation resistance, and can extend the tool life. With the goal.

The inventor of the present invention has conducted extensive research on extending the tool life of a cermet sintered body. As a result, the inventors have found that the tool life of the sintered cermet can be extended, and have completed the present invention.

That is, the gist of the present invention is as follows.
[1]
A cermet sintered body containing a hard phase and a binder phase,
The hard phase is a phase containing carbonitrides, carbides or nitrides containing at least one selected from the group consisting of Ti, W, Mo, Cr, Ta, Nb, V, Hf and Zr,
The binder phase is a phase containing at least one selected from the group consisting of Co, Ni and Fe,
The content of the hard phase is 82% by mass or more and 93% by mass or less,
The content of the binder phase is 7% by mass or more and 18% by mass or less,
The hard phase is
(i) a first hard phase having a cubic crystal structure exhibiting a diffraction peak derived from the (422) plane at a position of 123.5° or more and 125.0° or less in X-ray diffraction (XRD) measurement;
(ii) a second hard phase having a cubic crystal structure exhibiting a diffraction peak derived from the (422) plane at a position of 121.0° or more and less than 123.5° in X-ray diffraction (XRD) measurement;
including
The residual stress of the second hard phase is -1000 MPa or more and -600 MPa or less,
The residual stress of the binder phase is -600 MPa or more and -200 MPa or less,
The thickness of the first hard phase enriched region is 0 μm or more and 1.0 μm or less,
A cermet sintered body having a surface bonding phase ratio of 0.80 or more and 0.95 or less.
[2]
The cermet sintered body according to [1], wherein the surface nitrogen ratio is 0.42 or more and 0.50 or less.

INDUSTRIAL APPLICABILITY The cermet sintered body of the present invention is excellent in fracture resistance, wear resistance and plastic deformation resistance, and can extend tool life.

It is an example of a backscattered electron (BSE) observation image of a cross-sectional structure inside a cermet sintered body.

EMBODIMENT OF THE INVENTION Hereinafter, although the form (only henceforth "this embodiment") for implementing this invention is demonstrated in detail, this invention is not limited to the following this embodiment. Various modifications are possible for the present invention without departing from the gist thereof. In the drawings, the same elements are denoted by the same reference numerals, and overlapping descriptions are omitted. In addition, unless otherwise specified, positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings. Furthermore, the dimensional ratios of the drawings are not limited to the illustrated ratios.

The cermet sintered body of the present embodiment includes a hard phase and a binder phase, and the hard phase is at least one selected from the group consisting of Ti, W, Mo, Cr, Ta, Nb, V, Hf and Zr. A phase containing carbonitrides, carbides or nitrides containing carbonitrides, a phase containing at least one selected from the group consisting of Co, Ni and Fe, and a hard phase content of 82% by mass or more 93% by mass or less, the binder phase content is 7% by mass or more and 18% by mass or less, and the hard phase is (i) X-ray diffraction (hereinafter also referred to as “XRD”) measurement at 123.5° (ii) a first hard phase having a cubic crystal structure exhibiting a diffraction peak derived from the (422) plane at a position of 125.0 ° or less, and (ii) a position of 121.0 ° or more and less than 123.5 ° in XRD measurement a second hard phase having a cubic crystal structure exhibiting a diffraction peak derived from the (422) plane at a position, wherein the residual stress of the second hard phase is −1000 MPa or more and −600 MPa or less, and the binder phase remains The stress is −600 MPa or more and −200 MPa or less, and the thickness of the first hard phase-enriched region calculated by the following method (hereinafter also simply referred to as “the thickness of the first hard phase-enriched region”) is 0 μm or more. It is 1.0 µm or less, and the surface-bonded phase ratio calculated by the following method (hereinafter also simply referred to as "surface-bonded phase ratio") is 0.80 or more and 0.95 or less.
(Method for calculating the thickness of the first hard phase-enriched region)
In the backscattered electron (hereinafter also referred to as “BSE”) observation image of the cross section perpendicular to the surface of the sintered cermet body, the draw a line Assuming that the length of the line segment is 100%, the shortest distance between the line segment whose ratio of the line segment crossing the first hard phase is less than 30% and the surface of the cermet sintered body is defined as the first hard phase enrichment Let it be the thickness of the region. At this time, the length of the line segment was set to 20 μm or more.
(Method for calculating surface-bonded phase ratio)
In a cross section perpendicular to the surface of the cermet sintered body, using a scanning electron microscope (hereinafter also referred to as "SEM") with an energy dispersive X-ray spectrometer (hereinafter also referred to as "EDS"), the cermet sintered body surface Mass % of Co, Ni and Fe is analyzed at a position 10 μm further inward (surface portion) and a position (inside) 500 μm or more inward from the surface of the cermet sintered body. Analysis by EDS is performed by area analysis of a 10 μm×10 μm area centered on the above analysis position. A value obtained by dividing the sum of the mass % of Co, Ni and Fe in the surface part by the sum of the mass % of Co, Ni and Fe in the inside is defined as the surface bonding phase ratio.

The factors that enable such a cermet sintered body to have excellent chipping resistance, improve wear resistance and plastic deformation resistance, and extend the tool life are not clear in detail, but the present inventors considers the factors to be as follows. However, the factor is not limited to this. That is, when the content of the hard phase is 82% by mass or more, the cermet sintered body has improved hardness and excellent wear resistance and plastic deformation resistance. On the other hand, when the content of the hard phase is 93% by mass or less, the content of the binder phase is relatively increased, so that the cermet sintered body has improved toughness and excellent chipping resistance. Moreover, when the content of the binder phase is 7% by mass or more, the cermet sintered body has improved toughness and excellent chipping resistance. On the other hand, when the content of the binder phase is 18% by mass or less, the content of the hard phase relatively increases, so that the cermet sintered body has improved hardness, wear resistance and plastic deformation resistance. Excellent. Further, when the residual stress of the second hard phase is -1000 MPa or more, embrittlement of the hard phase is suppressed, and the fracture resistance of the cermet sintered body is improved. On the other hand, when the residual stress of the second hard phase is −600 MPa or less, the toughness of the hard phase is improved, and the cermet sintered body is excellent in fracture resistance. Further, when the residual stress of the binder phase is -600 MPa or more, embrittlement of the binder phase is suppressed, and the fracture resistance of the cermet sintered body is improved. On the other hand, when the residual stress of the binder phase is -200 MPa or less, the toughness of the binder phase is improved, and the cermet sintered body is excellent in fracture resistance. Furthermore, when the residual stress of the binder phase is -200 MPa or less, the binder phase hardens and the wear resistance of the cermet sintered body is improved. Further, when the thickness of the first hard phase-enriched region is 1.0 μm or less, the cermet sintered body has improved wear resistance and plastic deformation resistance. Further, when the surface binding phase ratio is 0.80 or more, the ratio of the binding phase is relatively increased, so that the cermet sintered body is excellent in fracture resistance. On the other hand, when the surface bonding phase ratio is 0.95 or less, the hard phase ratio relatively increases, so that the cermet sintered body is excellent in wear resistance and plastic deformation resistance. Combined with these effects, the cermet sintered body of the present embodiment is excellent in chipping resistance, improves wear resistance and plastic deformation resistance, and can extend tool life.

In the cermet sintered body of the present embodiment, the hard phase is a carbonitride, carbide or nitride containing at least one selected from the group consisting of Ti, W, Mo, Cr, Ta, Nb, V, Hf and Zr. It is preferably a phase containing carbonitrides and carbides containing at least one selected from the group consisting of Ti, W, Mo, Cr, Ta, Nb and Zr, Ti, W, More preferably, the phase contains a carbonitride containing at least one selected from the group consisting of Mo, Nb and Zr.

A specific composition constituting the hard phase is not particularly limited, but examples include TiC, TiN, TiCN, WC, TaC, NbC, ZrC, _Mo2C , _{Cr3C2 ,} VC, HfC, and the like. Among them, TiCN, WC, _TaC , NbC, ZrC, _Mo2C and _Cr3C2 are preferred, and TiCN, WC, NbC, ZrC and _Mo2C are more preferred.

In the cermet sintered body of the present embodiment, the binder phase is a phase containing at least one selected from the group consisting of Co, Ni and Fe, and at least one selected from the group consisting of Co and Ni. It is preferably a phase, more preferably a phase composed of Co and Ni.

In the cermet sintered body of this embodiment, the content of the hard phase is 82% by mass or more and 93% by mass or less. When the content of the hard phase is 82% by mass or more, the cermet sintered body has improved hardness and excellent wear resistance and plastic deformation resistance. On the other hand, when the content of the hard phase is 93% by mass or less, the content of the binder phase is relatively increased, so that the cermet sintered body has improved toughness and excellent chipping resistance. From the same point of view, the content of the hard phase is preferably 84% by mass or more and 90% by mass or less, more preferably 85% by mass or more and 88% by mass or less.

In the cermet sintered body of the present embodiment, the binder phase content is 7% by mass or more and 18% by mass or less. When the binder phase content is 7% by mass or more, the cermet sintered body has improved toughness and excellent chipping resistance. On the other hand, when the content of the binder phase is 18% by mass or less, the content of the hard phase relatively increases, so that the cermet sintered body has improved hardness, wear resistance and plastic deformation resistance. Excellent. From the same point of view, the content of the binder phase is preferably 10% by mass or more and 16% by mass or less, and more preferably 12% by mass or more and 15% by mass or less.

In the present embodiment, the content ratio (% by mass) of the hard phase and the binder phase is at least one selected from the group consisting of Ti, W, Mo, Cr, Ta, Nb, V, Hf and Zr. It is the value of the content ratio (% by mass) with respect to the total 100% by mass of the carbonitride, carbide or nitride containing and at least one selected from the group consisting of Co, Ni and Fe.
Further, in the present embodiment, the content ratio (% by mass) of the hard phase and the binder phase can be measured by analyzing using EDS at a position 500 μm or more inward from the surface of the cermet sintered body. . Analysis by EDS is performed by area analysis of a 10 μm×10 μm area centered on the above analysis position. At this time, Ti was calculated as a carbonitride, and W, Mo, Cr, Ta, Nb, and Zr were converted as carbides, and the content ratio (% by mass) of each phase was calculated. Specifically, the content ratio (% by mass) of the hard phase and the binder phase can be measured by the method described in Examples below.

In the cermet sintered body of the present embodiment, the hard phase has (i) a cubic crystal structure that exhibits a diffraction peak derived from the (422) plane at a position of 123.5° or more and 125.0° or less in XRD measurement. (ii) in XRD measurement, a second hard phase having a cubic crystal structure that exhibits a diffraction peak derived from the (422) plane at a position of 121.0° or more and less than 123.5°; including.

In this embodiment, the first hard phase and the second hard phase can be identified by BSE observation images of the internal cross-sectional structure of the cermet sintered body. FIG. 1 is an example of a BSE observation image of a cross-sectional structure inside a cermet sintered body. In the BSE observation image, the portion with black contrast is the first hard phase (1), and the portion with gray to white contrast is the second hard phase (6) (second hard phase a (2) , another second hard phase b(3), yet another second hard phase c(4)), and the elongated white part between these hard phases is the binder phase (5).

In the cermet sintered body of this embodiment, the ratio between the first hard phase and the second hard phase is evaluated as follows. The integrated intensity is calculated for the two diffraction peaks originating from each hard phase identified in the above XRD measurements for the hard phase. Ratio of the integrated intensity of the diffraction peak derived from the (422) plane of the first hard phase to the integrated intensity of the diffraction peak derived from the (422) plane of the second hard phase (first hard phase: second hard phase) is preferably 1.0:1.5 to 1.0:3.5, more preferably 1.0:2.0 to 1.0:3.0.

The first hard phase is a phase containing carbonitrides, carbides or nitrides containing at least one selected from the group consisting of Ti, W, Mo, Cr, Ta, Nb, V, Hf and Zr, and Ti , W, Mo, Cr, Ta, Nb and Zr. A phase containing a carbonitride containing at least one more selected species is more preferred.

The second hard phase is a phase containing carbonitrides, carbides or nitrides containing at least one selected from the group consisting of Ti, W, Mo, Cr, Ta, Nb, V, Hf and Zr, and Ti , W, Mo, Cr, Ta, Nb and Zr. More preferably, the phase contains a carbonitride containing at least one more selected species.

In the cermet sintered body of the present embodiment, the residual stress of the second hard phase is −1000 MPa or more and −600 MPa or less. When the residual stress of the second hard phase is -1000 MPa or more, embrittlement of the hard phase is suppressed, and the fracture resistance of the cermet sintered body is improved. On the other hand, when the residual stress of the second hard phase is -600 MPa or less, the toughness of the hard phase is improved, and the cermet sintered body is excellent in fracture resistance. From the same point of view, the residual stress of the second hard phase is preferably −950 MPa or more and −650 MPa or less, more preferably −900 MPa or more and −700 MPa or less.

Residual stress is the internal stress (intrinsic strain) remaining in the hard phase and bonding phase, and the stress generally represented by a numerical value of "-" (minus) is called compressive stress, and "+" (plus) The stress represented by the numerical value of is called tensile stress. In this embodiment, when expressing the magnitude of residual stress, the larger the numerical value of "+" (plus), the greater the residual stress, and the larger the numerical value of "-" (minus), the greater the residual stress. It is assumed that the residual stress is small.

In addition, in this embodiment, the residual stress of the second hard phase can be measured by the sin ² ψ method using XRD. The diffraction peak derived from the (422) plane of the second hard phase having a cubic crystal structure is used for evaluation. The peak exists at a position of 121.0° or more and less than 123.5° in 2θ-θ measurement. Specifically, the residual stress of the second hard phase can be measured by the method described in Examples below.

In the cermet sintered body of this embodiment, the residual stress of the binding phase is −600 MPa or more and −200 MPa or less. When the residual stress of the binder phase is -600 MPa or more, embrittlement of the binder phase is suppressed, and the fracture resistance of the cermet sintered body is improved. On the other hand, when the residual stress of the binder phase is -200 MPa or less, the toughness of the binder phase is improved, and the cermet sintered body is excellent in fracture resistance. Furthermore, when the residual stress of the binding phase is -200 MPa or less, the binding phase hardens and the wear resistance of the cermet sintered body is improved. From the same point of view, the residual stress of the binder phase is preferably −550 MPa or more and −250 MPa or less, more preferably −500 MPa or more and −300 MPa or less.

In addition, in this embodiment, the residual stress of the binder phase can be measured by the sin ² ψ method using XRD. Of the diffraction peaks derived from the binding phase having a cubic crystal structure, the diffraction peak derived from the (311) plane is used for evaluation. The peak is located between 89.5° and 93.0° in the 2θ-θ measurement. Specifically, the residual stress of the binder phase can be measured by the method described in Examples below.

In the cermet sintered body of the present embodiment, the thickness of the first hard phase enriched region is 0 μm or more and 1.0 μm or less. When the thickness of the first hard phase-enriched region is 1.0 μm or less, the cermet sintered body has improved wear resistance and plastic deformation resistance. From the same point of view, the thickness of the first hard phase-enriched region is preferably 0.5 μm or less, more preferably 0 μm.

In addition, in the present embodiment, the thickness of the first hard phase enriched region is calculated by the following method. First, in the BSE observation image of the cross section perpendicular to the surface of the sintered cermet body, line segments parallel to the surface of the sintered cermet body are drawn at intervals of 0.5 μm from the surface of the sintered cermet body inward. Assuming that the length of the line segment is 100%, the shortest distance between the line segment whose ratio of the line segment crossing the first hard phase is less than 30% and the surface of the cermet sintered body is defined as the first hard phase enrichment Let it be the thickness of the region. At this time, the length of the line segment was set to 20 μm or more.

In the cermet sintered body of the present embodiment, the surface bonding phase ratio is 0.80 or more and 0.95 or less. When the surface binding phase ratio is 0.80 or more, the ratio of the binding phase is relatively increased, so that the cermet sintered body has excellent fracture resistance. On the other hand, when the surface bonding phase ratio is 0.95 or less, the hard phase ratio increases relatively, so that the cermet sintered body is excellent in wear resistance and plastic deformation resistance. From the same point of view, the surface bonding phase ratio is preferably 0.81 or more and 0.91 or less, more preferably 0.83 or more and 0.88 or less.

In addition, in this embodiment, the surface-bonded phase ratio is calculated by the following method. First, using EDS, at a position 10 μm inward from the surface of the cermet sintered body (surface portion) and at a position 500 μm or more inward from the surface of the cermet sintered body (inside), mass % of Co, Ni and Fe to analyze. Analysis by EDS is performed by area analysis of a 10 μm×10 μm area centered on the above analysis position. A value obtained by dividing the sum of mass % of Co, Ni and Fe in the surface part by the sum of mass % of Co, Ni and Fe in the inside is defined as the surface bonding phase ratio.

In the cermet sintered body of the present embodiment, the surface nitrogen ratio (hereinafter also simply referred to as "surface nitrogen ratio") calculated by the following method is preferably 0.42 or more and 0.50 or less.
(Calculation method of surface nitrogen ratio)
EDS is used to analyze mass % of N element and C element at a position 10 μm inward from the surface of the cermet sintered body. Analysis by EDS is performed by area analysis of a 10 μm×10 μm area centered on the above analysis position. The ratio of the N element to the sum of the N element and the C element is defined as the surface nitrogen ratio.

In the cermet sintered body of the present embodiment, when the surface nitrogen ratio is 0.42 or more, it indicates that a certain amount of N element is included, and the hard particles are less likely to react with the work material during cutting. Progression of wear is suppressed, and wear resistance tends to improve. Moreover, when the surface nitrogen ratio is 0.42 or more, the machined surface of the work material tends to be excellent. On the other hand, when the surface nitrogen ratio is 0.50 or less, vacancies due to denitrification are suppressed during sintering, and the cermet sintered body tends to be excellent in fracture resistance. From the same point of view, the surface nitrogen ratio is more preferably 0.43 or more and 0.48 or less, and further preferably 0.44 or more and 0.46 or less.

Next, an example of the method for producing the cermet sintered body of this embodiment will be described. In addition, the method for manufacturing the cermet sintered body of the present embodiment is not particularly limited as long as the above configuration can be achieved.

The method for producing a cermet sintered body of the present embodiment includes, for example, steps 1 to 11 below.

Step 1 is a step of blending each raw material powder (blending step). Specifically, although not particularly limited, for example, at least one selected from the group consisting of Ti, W, Mo, Cr, Ta, Nb, V, Hf and Zr having an average particle size of 0.5 to 4.0 μm 82 to 93% by mass of at least one powder selected from the group consisting of carbonitrides, carbides or nitrides containing seeds, and a group consisting of Co, Ni and Fe having an average particle size of 0.5 to 3.0 μm A step of blending 7 to 18% by mass of at least one selected powder (where the total of these is 100% by mass) can be mentioned. Specific examples of raw material powders are not particularly limited, but include TiC _0.5 N _0.5 , TiC _0.3 N _0.7 , WC, TaC, NbC, ZrC, Mo ₂ C, Cr ₃ C ₂ , VC, HfC, Co, Ni and Powders, such as Fe, are mentioned.

Step 2 is a step (mixing step) of mixing the raw material powders blended in step 1 with a solvent by a wet ball mill. Here, the mixing time of each raw material powder is preferably 10 to 40 hours.

Step 3 is a step of drying the powder mixed in step 2 (drying step). Here, the drying temperature is preferably 100° C. or less.

Step 4 is a step (forming step) of forming the mixed powder dried in step 3 into a predetermined shape. Specifically, in the molding step, for example, it is preferable to press and mold the mixed powder using a mold having a predetermined tool shape. Furthermore, in the molding process, the addition of paraffin, for example, tends to improve moldability.

Step 5 is a step (first temperature raising step) of raising the temperature of the compact obtained in step 4 from room temperature to a predetermined temperature (reaching temperature) in a vacuum atmosphere. The temperature reached in the first heating step is the starting temperature of the second heating step, and is preferably 1300 to 1440° C., for example. In the first temperature raising step, the pressure is preferably 70 Pa or less.

Step 6 is a step (second temperature raising step) of heating the compact to a predetermined temperature (reaching temperature) in an N ₂ gas atmosphere after step 5. It is preferable that the starting temperature of the second heating step is, for example, 1300 to 1440.degree. The temperature reached in the second heating step is the temperature in the sintering step, and is preferably 1450 to 1550°C. In the second heating step, the pressure is preferably 133-6650Pa.

Step 7 is a step (sintering step) of holding and sintering the compact at a predetermined temperature in an N ₂ gas atmosphere after step 6 . Here, the sintering temperature is preferably 1450 to 1550°C, more preferably 1480 to 1550°C. In the sintering step, the pressure is preferably 70-600Pa. The sintering time is preferably 30 to 120 minutes.

Step 8: A step of cooling the cermet sintered body obtained in Step 7 to a predetermined temperature in a vacuum atmosphere (first cooling step). Here, the first cooling start temperature is the sintering temperature, and is preferably 1450 to 1550° C., for example. It is preferable that the first cooling ultimate temperature is, for example, 1300 to 1350.degree. In the first cooling step, the cooling rate is preferably 20° C./min or less, more preferably 3 to 15° C./min. In the first cooling step, the pressure is preferably 133 Pa or less.

Step 9 is a step of cooling the cermet sintered body to room temperature in an inert gas atmosphere after step 8 (second cooling step). Here, the second cooling start temperature is the first cooling target temperature, and is preferably 1300 to 1350° C., for example. The second cooling target temperature is room temperature. In the second cooling step, the pressure is preferably 133-300000Pa. In the second cooling step, specific examples of the inert gas atmosphere include, but are not limited to, He, Ne and Ar gas atmospheres.

Step 10 is a step (honing step) of honing the cutting edge of the sintered cermet body after step 9. Here, the desired honing shape is adjusted.

Step 11 is a step (blasting step) of blasting particles of a blasting material such as alumina (Al ₂ O ₃ ) against the surface of the cermet sintered body after step 10 . Here, the method of the blasting process is preferably dry. In the blasting process, the average particle diameter of the particles of the blasting material is preferably 100 to 150 μm. In the blasting process, the projection angle (inclination angle from the normal line of the rake face of the tool when formed into the shape of the tool) is preferably 30 to 60 degrees. In the blasting process, the projection speed is preferably 70-150 m/sec, more preferably 70-130 m/sec.

The average particle size of the raw material powder used in step 1 can be measured by Fisher Sub-Sieve Sizer (FSSS) described in American Society for Testing and Materials (ASTM) Standard B330.

Each step of the method for producing a cermet sintered body of the present embodiment has the following significance.

In step 1 (blending step), the composition of the cermet sintered body can be adjusted to a desired composition by adjusting the blending ratio of each raw material powder.

In step 2 (mixing step), a mixture can be obtained by uniformly mixing raw material powders having a predetermined composition. Also, the grain size of the raw material powder can be adjusted to adjust the structure and grain size of the sintered body.

In step 3 (drying step), a mixed powder can be obtained by evaporating the solvent from the mixture.

In step 4 (forming step), a molded body having a predetermined tool shape is obtained from the mixed powder. Addition of paraffin improves moldability.

In step 5 (first temperature raising step), degassing can be promoted before and immediately after the appearance of the liquid phase, and sinterability in step 7 (sintering step) below can be improved.

In step 6 (second temperature raising step), the temperature can be raised to the sintering temperature while suppressing denitrification from the compact. By combining this step 6 (second temperature rising step) and the following step 7 (sintering step), the surface bonding phase ratio can be reduced.

In step 7 (sintering step), the molded body is held at a predetermined temperature and sintered to obtain a cermet sintered body and to reduce the surface bonding phase ratio.

In step 8 (first cooling step), a first hard phase enriched region can be formed. Also, the surface nitrogen ratio can be adjusted.

In step 9 (second cooling step), the cermet sintered body can be cooled to room temperature.

In step 10 (honing step), the cutting edge of the tool-shaped cermet sintered body can be provided with a predetermined honing shape.

In step 11 (blasting step), a compressive residual stress can be applied to the second hard phase and the binder phase. As a method of blasting, dry blasting can impart higher compressive residual stress than wet blasting. On the other hand, wet blasting tends to have a stronger force for grinding the surface of the sintered body than dry blasting.

In the cermet sintered body of the present embodiment, the method for forming the two hard phases of the first hard phase and the second hard phase is not particularly limited, but for example, a raw material made of carbonitride, carbide or nitride Powders of Ti carbonitrides, carbides or nitrides, and carbonitrides, carbides or nitrides containing at least one selected from the group consisting of W, Mo, Cr, Ta, Nb, V, Hf and Zr By using nitride powder, the first hard phase and the second hard phase can be obtained in the above-described manufacturing method. In addition, when the compounding ratio of the Ti carbonitride, carbide, or nitride powder to be blended is increased, the integrated intensity of the diffraction peak derived from the (422) plane of the first hard phase identified by XRD measurement tends to increase. be.

As a method of controlling the thickness of the first hard phase-enriched region within a desired range, there is a method of adjusting the starting temperature of the second heating step (reaching temperature of the first heating step) in the above-described manufacturing method. be done. Specifically, if the starting temperature of the second heating step is increased within the range of the starting temperature of the second heating step (1300 to 1440° C.), the thickness of the first hard phase-enriched region becomes smaller. There is a tendency.

As a method for controlling the surface bonding phase ratio within a desired range, in the above-described manufacturing method, a dry blasting process is adopted instead of a wet blasting process, and the starting temperature of the second heating process (first heating process (reaching temperature), adjusting the cooling rate in the first cooling step, or adjusting the sintering temperature in the sintering step. Specifically, as a method of the blasting process, a dry method is adopted instead of a wet method, the starting temperature of the second heating step is lowered, the cooling rate of the first cooling step is slowed down, and the sintering step is performed. As the bonding temperature increases, the surface bonding phase ratio tends to decrease.

As a method for controlling the residual stress of the second hard phase within a desired range, a method of adopting a dry blasting process instead of a wet blasting process in the above-described production method and adjusting the blasting speed in the blasting process can be mentioned. be done. Specifically, when a dry blasting process is adopted instead of a wet blasting process and the blasting speed of the blasting process is increased, the residual stress of the second hard phase tends to decrease.

As a method of controlling the residual stress of the binder phase within a desired range, a method of adopting a dry blasting process instead of a wet blasting process in the above-described manufacturing method and adjusting the blasting speed of the blasting process can be mentioned. Specifically, when a dry blasting process is adopted instead of a wet blasting process and the blasting speed of the blasting process is increased, the residual stress of the second hard phase tends to decrease.

As a method for controlling the surface nitrogen ratio to a desired range, in the above-described manufacturing method, a dry blasting process is adopted instead of a wet blasting process, and the starting temperature of the second heating process (the starting temperature of the first heating process temperature), adjusting the cooling rate in the first cooling step, or adjusting the sintering temperature in the sintering step. Specifically, as a method of the blasting process, a dry method is adopted instead of a wet method, the starting temperature of the second heating step is lowered, the cooling rate of the first cooling step is slowed down, and the sintering step is performed. As the condensation temperature increases, the surface nitrogen ratio tends to decrease.

The surface of the cermet sintered body of the present embodiment may be further coated with a hard film by a conventional physical vapor deposition method or chemical vapor deposition method.

Although the cermet sintered body of the present embodiment is not particularly limited, it can be used for, for example, indexable cutting inserts for milling or turning, drills, end mills, and the like.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples.

(Example 1)
[Production of cermet sintered body]
As raw material powders, commercially available TiC _0.5 N _0.5 powder with an average particle size of 2.0 μm, TiC _0.3 N _0.7 powder with an average particle size of 2.0 μm, WC powder with an average particle size of 1.5 μm, and an average particle size of 1.5 μm. 5 μm TaC powder, 1.5 μm average particle size NbC powder, 1.5 μm average particle size ZrC powder, 1.5 μm average particle size Mo ₂ C powder, 1.5 μm average particle size Cr ₃ C ₂ powder, Co powder with an average particle size of 1.0 μm and Ni powder with an average particle size of 1.0 μm were prepared. The average particle diameter of the raw material powder was measured by Fisher Sub-Sieve Sizer (FSSS) described in American Society for Testing and Materials (ASTM) Standard B330.

The prepared raw material powders were weighed so as to have the composition shown in Table 1 below, and each weighed raw material powder was placed in a stainless steel pot together with an acetone solvent and cemented carbide balls, and mixed and pulverized in a wet ball mill. Mixing and pulverization time by a wet ball mill was 15 hours.

After mixing and grinding with a wet ball mill, the mixture was dried at 60° C. to evaporate the acetone solvent and obtain a mixed powder.

After adding 3.0% by mass of paraffin to the obtained powder mixture, the powder mixture was press-molded at a pressure of 100 MPa using a mold having an insert shape of TNMG160404 after sintering to obtain a compact of the powder mixture.

The obtained compact was heated from room temperature to the start temperature of the second heating step shown in Table 2 in a vacuum atmosphere (first heating step). Moreover, the pressure was set to 50 Pa in the first temperature raising step.

After that, the compact was heated from the starting temperature of the second heating step shown in Table 2 to the temperature of the sintering step shown in Table 2 in an N ₂ gas atmosphere (second heating step). The pressure was set to 600 Pa in the second temperature raising step.

After that, the compact was sintered in an N ₂ gas atmosphere while being held at the temperature of the sintering process shown in Table 2 (sintering process). In the sintering process, the pressure was 270 Pa and the sintering time was 60 minutes.

The obtained cermet sintered body was cooled from the temperature of the sintering step shown in Table 2 to 1350° C. in a vacuum atmosphere (first cooling step). again. In the first cooling step, the cooling rate was as shown in Table 2, and the pressure was 90 Pa.

Thereafter, the cermet sintered body was cooled from the first cooling ultimate temperature of 1350° C. to room temperature in an Ar gas atmosphere (second cooling step). Moreover, the pressure was set to 100000 Pa in the second cooling step.

After that, the cutting edge of the sintered cermet was subjected to round honing treatment with a SiC brush (honing process).

After that, a blasting step was performed in which alumina (Al ₂ O ₃ ) particles as a blasting material collided with the surface of the cermet sintered body. The method of the blasting process was as shown in Table 2. In the blasting process, the average particle diameter of the particles of the projection material was set to 120 μm, and the projection angle was set to 45 degrees. Also, the projection speed was set as shown in Table 2.

Invention products 1 to 16 and comparative products 1 to 13 were produced as described above.

The cermet sintered bodies of invention products 1 to 16 and comparative products 1 to 13 were observed with an SEM with EDS at a position 500 μm inward from the surface of the cermet sintered body in the cross section perpendicular to the cermet sintered body surface. and identified the compositions of the hard and binder phases.
In addition, the content ratio (% by mass) of the hard phase and the binder phase in the cermet sintered bodies of Invention Products 1 to 16 and Comparative Products 1 to 13 was measured using EDS, and the cermet It was measured by analysis using EDS at a position 500 μm inward from the surface of the sintered body. The EDS analysis was carried out by area analysis of a 10 μm×10 μm area centered on the above analysis position. At this time, Ti is carbonitride, W, Mo, Cr, Ta, Nb and Zr are carbides, and the converted values were calculated as the content ratio (% by mass) of each phase. Table 3 shows the results.

XRD measurement was performed on the cermet sintered bodies of Invention Products 1 to 16 and Comparative Products 1 to 13, and cubic crystals exhibiting a diffraction peak derived from the (422) plane at a position of 123.5 ° or more and 125.0 ° or less. A first hard phase having a structure and a second hard phase having a cubic crystal structure exhibiting a diffraction peak derived from the (422) plane at a position of 121.0° or more and less than 123.5°. bottom. In invention products 1 to 16, the ratio of the integrated intensity of the diffraction peak derived from the (422) plane of the first hard phase to the integrated intensity of the diffraction peak derived from the (422) plane of the second hard phase (first hard phase: second hard phase) was in the range of 1.0:2.0 to 1.0:2.7. Specifically, the above XRD measurement was performed by the following method. Using an X-ray diffractometer RINT TTRIII (product name) manufactured by Rigaku Co., Ltd., X-ray diffraction of a 2θ/θ focusing optical system using Cu—Kα rays was performed under the following conditions. Peak intensity was measured. Here, the measurement conditions are as follows: output: 50 kV, 250 mA, incident side solar slit: 5°, divergence vertical slit: 2/3°, divergence vertical limiting slit: 5 mm, scattering slit 2/3°, light receiving side solar slit: 5° , light receiving slit: 0.3 mm, BENT monochromator, light receiving monochrome slit: 0.8 mm, sampling width: 0.01°, scan speed: 4°/min, 2θ measurement range: 20° to 140°.

The first hard phase and the second hard phase were identified by BSE observation images of the internal cross-sectional structure of the cermet sintered body.

For the cermet sintered bodies of Invention Products 1 to 16 and Comparative Products 1 to 13, the residual stress of the second hard phase was measured by the sin ² ψ method using XRD. Evaluation was made using the diffraction peak derived from the (422) plane of the second hard phase having a cubic crystal structure. The peak was present at a position of 121.0° or more and less than 123.5° in 2θ-θ measurement. Table 4 shows the results.

For the cermet sintered bodies of Invention Products 1 to 16 and Comparative Products 1 to 13, the residual stress in the binder phase was measured by the sin ² ψ method using XRD. Of the diffraction peaks derived from the binding phase having a cubic crystal structure, the diffraction peak derived from the (311) plane was used for evaluation. The peak was located between 89.5° and 93.0° in the 2θ-θ measurement. Table 4 shows the results.

For the cermet sintered bodies of Invention Products 1 to 16 and Comparative Products 1 to 13, the thickness of the first hard phase enriched region was calculated by the following method. First, in the BSE observation image of the cross section perpendicular to the surface of the sintered cermet body, line segments parallel to the surface of the sintered cermet body were drawn at intervals of 0.5 μm from the surface of the sintered cermet body inward. Assuming that the length of the line segment is 100%, the shortest distance between the line segment whose ratio of the line segment crossing the first hard phase is less than 30% and the surface of the cermet sintered body is defined as the first hard phase enrichment It is the thickness of the area. At this time, the length of the line segment was set to 20 μm. Table 4 shows the results.

For the cermet sintered bodies of invention products 1 to 16 and comparative products 1 to 13, the surface bonding phase ratio was calculated by the following method. First, using EDS, at a position 10 μm inward from the surface of the cermet sintered body (surface portion) and at a position 500 μm or more inward from the surface of the cermet sintered body (inside), mass % of Co, Ni and Fe was analyzed. The EDS analysis was carried out by area analysis of a 10 μm×10 μm area centered on the above analysis position. A value obtained by dividing the sum of the mass % of Co, Ni and Fe in the surface part by the sum of the mass % of Co, Ni and Fe in the inside was defined as the surface bonding phase ratio. Table 4 shows the results.

For the cermet sintered bodies of invention products 1 to 16 and comparative products 1 to 13, the surface nitrogen ratio was calculated by the following method. EDS was used to analyze mass % of N element and C element at a position 10 μm inward from the surface of the cermet sintered body. The EDS analysis was carried out by area analysis of a 10 μm×10 μm area centered on the above analysis position. The ratio of the N element to the sum of the N element and the C element was defined as the surface nitrogen ratio. Table 4 shows the results.

Cutting test 1 and cutting test 2 were performed using the cermet sintered bodies of invention products 1 to 16 and comparative products 1 to 13 obtained. Cutting test 1 evaluates chipping resistance, and cutting test 2 evaluates wear resistance and plastic deformation resistance. The results of cutting tests 1 and 2 are shown in Table 5.

[Cutting test 1]
Work material: SCM415,
Work material shape: A round bar with two equally spaced grooves on the side,
Cutting speed: 200m/min,
depth of cut: 1.0 mm,
Feed: 0.15mm/rev. ,
Coolant: Wet,
Insert: TNMG160404,
Evaluation item: The tool life was defined as the time when the cutting edge of the tool became chipped, and the number of impacts until the tool life was measured.

[Cutting test 2]
Work material: S45C,
Work material shape: round bar,
Cutting speed: 250m/min,
depth of cut: 1.0 mm,
Feed: 0.20 mm/rev. ,
Coolant: Wet,
Insert: TNMG160404,
Evaluation item: The tool life was defined as when the cutting edge of the tool became chipped or when the flank wear width of the tool reached 0.2 mm, and the machining time until the tool life was measured.

The number of impacts up to the tool life in cutting test 1 was evaluated as A when 20000 times or more, B when 15000 times or more and less than 20000 times, and C when less than 15000 times. In addition, the machining time up to the tool life in cutting test 2 was evaluated as A for 30 minutes or more, B for 25 minutes or more and less than 30 minutes, and C for less than 25 minutes. In this evaluation, the order is (excellent) A>B>C (poor), and the more A, the better the cutting performance.

From the results in Table 5, all of the cermet sintered bodies of the invention have an evaluation of B or higher in both cutting tests 1 and 2, and are excellent in fracture resistance, wear resistance, and plastic deformation resistance. I understand. On the other hand, the comparative cermet sintered body was evaluated as C in at least one of cutting tests 1 and 2, and was found to be inferior in at least one of chipping resistance, wear resistance, and plastic deformation resistance. . From the above, it was found that the cermet sintered body of the invention is superior in cutting performance and has a longer tool life than the cermet sintered body of the comparative product.
In the cermet sintered body of Comparative Product 11, a large amount of the surface was scraped off, so it is considered that the surface bonding phase ratio increased. Therefore, it is considered that the cermet sintered body of Comparative Product 11 was inferior in cutting performance in cutting test 2 and had a short tool life.
When the conditions of the temperature in the second heating step, the temperature in the sintering step, and the cooling rate in the first cooling step are adjusted so that the ratio of the surface-bonded phase is smaller than that of Comparative Product 11, the sintered compact undergoes severe deformation, Since the target tool shape could not be obtained, the cutting performance could not be evaluated.

INDUSTRIAL APPLICABILITY The cermet sintered body of the present invention has excellent chipping resistance, wear resistance and plastic deformation resistance, and can extend the tool life as compared with the conventional sintered body, and therefore has high industrial applicability.

1: first hard phase, 2: second hard phase a, 3: another second hard phase b, 4: further second hard phase c, 5: binder phase, 6: second hard phase

Claims (2)

A cermet sintered body containing a hard phase and a binder phase,
The hard phase is a phase containing carbonitrides, carbides or nitrides containing at least one selected from the group consisting of Ti, W, Mo, Cr, Ta, Nb, V, Hf and Zr,
The binder phase is a phase containing at least one selected from the group consisting of Co, Ni and Fe,
The content of the hard phase is 82% by mass or more and 93% by mass or less,
The content of the binder phase is 7% by mass or more and 18% by mass or less,
The hard phase is
(i) a first hard phase having a cubic crystal structure exhibiting a diffraction peak derived from the (422) plane at a position of 123.5° or more and 125.0° or less in X-ray diffraction (XRD) measurement;
(ii) a second hard phase having a cubic crystal structure exhibiting a diffraction peak derived from the (422) plane at a position of 121.0° or more and less than 123.5° in X-ray diffraction (XRD) measurement;
including
The residual stress of the second hard phase is -1000 MPa or more and -600 MPa or less,
The residual stress of the binder phase is -600 MPa or more and -200 MPa or less,
The thickness of the first hard phase enriched region is 0 μm or more and 1.0 μm or less,
A cermet sintered body having a surface bonding phase ratio of 0.80 or more and 0.95 or less. The cermet sintered body according to claim 1, wherein the surface nitrogen ratio is 0.42 or more and 0.50 or less.

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