JP4974980B2 - TiCN-based cermet - Google Patents

Description

  The present invention relates to a TiCN-based cermet having both toughness and hardness suitable for cutting tool members, wear-resistant tool members, and the like.

  Conventionally, TiC-based cermets and TiCN-based cermets have been developed as wear-resistant tools and cutting tool alloys, and TiCN-based cermets with improved toughness have been widely used.

Such TiCN-based cermets are particularly required to have improved fracture resistance. For example, in JP-A-8-199283 (Patent Document 1), a solid solution state of a hard phase, specifically, a core part is required. Optimizes the ratio of the hard phase that has a black cored structure and the hard phase that has a white core structure, and the thermal shock generated by high-speed cutting, etc. by optimizing the particle size It is disclosed that the durability can be improved.
JP-A-8-199283

  However, the cermet disclosed in the above-mentioned JP-A-8-199283 also has insufficient durability against thermal shock, and there is a limit to improvement in cutting performance. Further improvement in thermal shock resistance and fracture resistance, There was a need for improved wear.

  The present invention is for solving the above-mentioned problems, and its purpose is to further improve the fracture resistance by optimizing the structure by optimizing the solid solution state of the hard phase of the TiCN-based cermet for each place and The purpose is to improve chipping resistance and wear resistance.

  In the present invention, by optimizing the particle size of the raw material powder and the firing conditions, the solid solution state of the hard phase is optimized according to each part, and the strength and hardness improvement by atomizing the hard phase inside the cermet, As a result of satisfying both the thermal shock resistance improvement on the cermet surface, it was found that both the fracture resistance and the wear resistance of the cermet as a whole improved.

That is, the TiCN-based cermet of the present invention includes TiCN and at least a part of carbide, nitride and carbonitride of at least one metal selected from W, Mo, Cr, Nb, Ta, Zr and V. The hard phase formed by solid solution
A TiCN-based cermet bonded with 1 to 30% by weight of a Co and / or Ni bonded phase,
80% by weight or more of Ti as a metal component, the total amount of at least one metal selected from W, Mo, Cr, Nb, Ta, Zr and V is 1 to 15% by weight, Co and / or Ni A first hard phase in which the total amount of binder phase metal is 0 to 3% by weight ;
Ti is 30 to 70% by weight, and the total amount of at least one metal selected from the above W, Mo, Cr, Nb, Ta, Zr and V is 70 to 30% by weight, Co and / or Ni binder phase The total amount of metal consists of a second hard phase consisting of 0 to 3% by weight ,
In the scanning electron micrograph (SEM) of the TiCN-based cermet arbitrary cross section,
The first hard phase is relatively blacker than the second hard phase,
The second hard phase is observed to be relatively grayish white than the first hard phase,
The hard phase has a double-core structure in which the first hard phase is a core part and the second hard phase is a peripheral part (however, not all of the hard phases have a core structure). )
The average particle diameter d _1in of the first hard phase inside the cermet is 0.05 to 0.5 μm, the area ratio S _1in of the first hard phase occupying the whole inside of the cermet is 40 to 80 area%, and The average particle diameter d _2in of the second hard phase inside the cermet is 0.6-2 μm,
The area ratio S _2in of the second hard phase occupying the entire interior of the cermet is 5 to 40% by area,
The average particle size _{d 1SF} of definitive cermet surface portion of the first hard phase is larger than _{d 1in} in 0.3～1Myuemu,
The area ratio _{S 1SF} of the first hard phase in the total of the cermet surface portion is from 5 to 40 area%, and the average particle diameter _{d 2SF} of the second hard phase in the cermet surface portion 1 to 3 [mu] m _{d 2in} Bigger,
Thickness area ratio _{S 2SF} in the second hard phase in the total of the cermet surface portion is composed of 50 to 80 area% is characterized in that there is a surface area of 20 to 100 [mu] m.

  According to the TiCN-based cermet of the present invention, the solid solution state of the hard phase is optimized according to each part, and the strength and hardness are improved by atomizing the hard phase inside the cermet, and the thermal shock resistance is improved on the cermet surface. As a result of satisfying both, the fracture resistance and wear resistance of the cermet as a whole are improved.

  FIG. 1 is a scanning electron micrograph (SEM) of an arbitrary cross section inside the TiCN-based cermet of the present invention (hereinafter simply abbreviated as cermet), and FIG. 2 is an SEM photograph of an arbitrary cross section including the surface. This will be explained based on the above.

  According to FIGS. 1 and 2, the TiCN-based cermet (hereinafter simply abbreviated as cermet) 1 of the present invention is at least one selected from the metals of the periodic table IVa, Va and VIa other than TiCN and Ti. Hard phase 2 in which at least a part of carbides, nitrides, and carbonitrides of seed metals are dissolved is bonded to hard phase 2 with 1 to 30% by weight of Co and / or Ni bonding phase 3. According to FIGS. 1 and 2, the hard phase 2 is composed of a black first hard phase 2a and an off-white second hard phase 2b.

According to the present invention, the average particle diameter d _1in of the first hard phase 2a inside the cermet 1 (FIG. 1) is 0.05 to 0.5 μm, and the area ratio of the first hard phase 2a occupying the whole inside of the cermet 1 The area ratio of the second hard phase 2b occupying the entire inside of the cermet 1 with S _1in being 40 to 80 area% and the average particle diameter d _2in of the second hard phase 2b inside the cermet 1 being 0.6 to ₂ μm. S _2in is composed of 5 to 40% by area, and the average particle diameter d _1sf of the first hard phase 2a on the surface of the cermet 1 (FIG. 2) is 0.3 to 1 μm, and the first hard occupies the entire surface of the cermet 1 area ratio _{S 1SF} phase 2a consists 5-40 area%, and an average particle diameter _{d 2SF} in the second hard phase 2b is 1~3μm in the cermet 1 surface, a second hard phase in the total of the cermet 1 surface portion b area ratio S _2SF is a significant feature that consists of 50 to 80 area%, thereby, it is possible to increase the strength of the cermet 1, the thermal conductivity of the cermet 1 surface, to increase the Young's modulus cermet 1 By improving the thermal shock resistance on the surface of the cermet, it is possible to improve the wear resistance and fracture resistance of the cermet 1 even under conditions that cause severe thermal shock such as high speed cutting, high feed cutting and wet cutting. .

Incidentally, the average particle size _(d 1, _{d 2)} and the area ratio _(S 1, _{S 2)} can be measured by using a commercially available image analysis apparatus with respect to a scanning electron micrograph (SEM) .

Here, when the average particle diameter d _1in of the first hard phase 2a inside the cermet ₁ is smaller than 0.05 μm, the structure becomes inhomogeneous due to aggregation of the hard phases, leading to a decrease in strength, and heat conduction inside the cermet 1. The rate drops. On the other hand, when d _1in exceeds 0.5 μm, the strength and hardness of the cermet 1 are lowered, and both the fracture resistance and the wear resistance are lowered. desired range of d _1in is 0.1 to 0.3 [mu] m. On the other hand, when the area ratio S _1in of the first hard phase 2a is less than 40 area% or more than 80 area%, the strength and hardness of the cermet 1 are lowered. A desirable range of S _1in is 50 to 70 area%.

Furthermore, if the average particle diameter d _2in of the second hard phase 2b in the cermet 1 is smaller than 0.6 μm, the hard phase 2 aggregates to form a non-uniform structure, and if d _2in exceeds ₂ μm, the second hard phase 2b The dispersion state becomes worse and the strength decreases. A desirable range of d _2in is 0.8 to 1.5 μm. In addition, when the area ratio S _2in of the second hard phase 2b in the cermet 1 is less than 5 area%, the cermet 1 is in a poorly sintered state and the strength is reduced, and when S _{2 in} is more than 40 area%, the cermet 1 is The average particle size of the entire hard phase 2 is increased and the strength is lowered. Desirable range of S _2in is 10 to 30 area%.

On the other hand, in the cermet 1 surface region, when the average particle diameter d _1sf of the first hard phase 2a is smaller than 0.3 μm, the thermal conductivity and the plastic deformation resistance are lowered, and conversely, when d _1sf exceeds 1 μm. The fracture resistance of the cermet 1 surface is reduced. A desirable range of d _1sf is 0.3 to 0.7 μm. On the other hand, if the area ratio S _1sf of the first hard phase 2a in the surface portion of the cermet 1 is less than 5 area%, the plastic deformation resistance of the cermet 1 is lowered, and conversely if it exceeds 40 area%, the heat conduction of the cermet 1 surface. And the thermal shock resistance is reduced. A desirable range of S _1sf is 7 to 25 area%.

Further, if the average particle diameter d _2sf of the second hard phase 2b in the cermet 1 surface region is smaller than 1 μm, the thermal conductivity and the plastic deformation resistance are lowered, and if d _2sf exceeds 3 μm, the fracture resistance of the cermet 1 surface is reduced. descend. A desirable range of d _2sf is 1.2 to 2 μm. Further, if the area ratio _S2sf of the second hard phase 2b in the surface portion of the cermet 1 is less than 50 area%, the thermal conductivity and plastic deformation resistance of the cermet 1 are lowered, and if _S2sf is more than 80 area%, the first. The deficiency of the surface of the cermet 1 is lowered due to insufficient hard phase and binder phase. A desirable range of S2sf is 60 to 75 area%.

  Further, according to the present invention, the black portion 2a is present at the center of the grayish white second hard phase 2b, and the ratio of the black portion 2a in the cermet 1 (FIG. 1) is the surface of the cermet 1 (FIG. 2). The presence of the black portion 2a is greater than the existence ratio of the black portion 2a to increase the strength of the cermet 1 by atomizing the hard phase 2 (2a, 2b) inside the cermet 1 and to dissolve the hard phase 2 (2a, 2b) on the cermet 1 It is desirable in terms of optimizing the state and increasing the thermal shock resistance of the cermet 1.

  Further, the first hard phase 2a preferably contains 80% by weight or more of Ti as a metal component, and in particular, Ti is 80 to 98% by weight of the metals of the periodic table IVa, Va and VIa other than Ti. At least one metal selected from the group consisting of at least one of W, Mo, Cr, Nb and V, and further W (referred to as a solid solution metal in the present invention) in a total amount of 1 to 15% by weight, Co and / or The total amount of Ni binder phase metal is 0 to 3% by weight.

  Furthermore, the grayish white second hard phase 2b preferably contains a large amount of solid solution metal relative to the first hard phase 2a, and in particular, Ti is 30 to 70 wt%, and the total amount of solid solution metal is 70 to 30 wt%. It is desirable that the total amount of the binder phase metal of%, Co and / or Ni is 0 to 3% by weight. The content ratio of the metal component in the hard phase can be measured by energy dispersive spectroscopy (EDS) of a transmission electron microscope (TEM).

  Further, according to the present invention, the hard phase 2 has a double-core structure in which the first hard phase 2a is a core part and the second hard phase 2b is a peripheral part. The cermet 1 has a fine and uniform structure and is excellent in wettability with the binder phase 3 so that it contributes to increasing the strength of the cermet 1, but all the hard phases 2 have a cored structure. It does not have to be. In the case of the cored structure, the area of the second hard phase 2b is the area of the annular portion excluding the area of the first hard phase 2a at the center.

Further, according to the present invention, the strength of the cermet 1, the hardness, in order to optimize the balance between thermal shock _{resistance, d 1sf / d 1in = 1~6} , d 2sf / d 2in = 1.5~1.7 _{, S 1sf / S 1in = 0.3~0.5} , it is desirable that the _{S 2sf} / _S 2in = _1.5~4.

  Further, in order to achieve both fracture resistance and wear resistance of the cermet 1, the thickness of the surface region is preferably 20 to 100 μm, particularly 30 to 50 μm.

  Note that it is desirable that the Vickers hardness in the cermet 1 takes a maximum value in the surface region, and the Vickers hardness gradually decreases toward the inside. Thereby, it can have both high abrasion resistance and defect resistance.

(Production method)
Next, the manufacturing method of the TiCN base cermet of this invention is demonstrated.

  First, TiCN powder having an average particle size of 0.1 to 1.2 μm, particularly 0.2 to 0.9 μm, TiN powder having an average particle size of 0.1 to 2 μm, the above-described solid solution metal carbide powder, nitride powder or A mixed powder obtained by mixing any one of the carbonitride powders with Co powder and / or Ni powder is prepared.

  According to the present invention, it is important to control the average particle size of the TiCN raw material powder in the range of 0.1 to 1.2 μm. If the average particle size is smaller than 0.1 μm, the raw material aggregates and the cermet Becomes a heterogeneous structure, and conversely, if it exceeds 1.2 μm, the cermet cannot be made the above-described structure.

  And a binder is added to this mixed powder, and it shape | molds in a predetermined shape by well-known shaping | molding methods, such as press molding, extrusion molding, and injection molding.

  Next, the molded body is heated from room temperature to a firing temperature A of 1150 to 1250 ° C. at a heating rate A of 0.7 ° C./min to 2 ° C./min, and from 1150 to 1250 ° C. to 1400 to 1500 ° C. The temperature is raised to a firing temperature B at a temperature rising rate B of 5 ° C./min to 15 ° C./min, and further to a firing temperature C of 1500 to 1600 ° C. than a temperature rising rate B of 4 ° C./min to 14 ° C./min. After the temperature is raised at a slow temperature rise rate C and held for a predetermined time, the temperature is lowered in a state of being filled with 10 to 150 Pa of an inert gas.

  According to the present invention, it is important to lower the temperature in the state where the firing rate is increased and the predetermined amount of inert gas is filled when the temperature is decreased, and the cermet having the structure described above is manufactured by the above manufacturing method. Can do.

  TiCN powder with an average particle size of 0.7 μm or 2 μm, TiN powder with an average particle size of 1.5 μm, TaC powder with an average particle size of 2 μm, NbC powder with an average particle size of 1.5 μm, WC powder with an average particle size of 1.1 μm A ZrC powder having an average particle diameter of 1.8 μm, a VC powder having an average particle diameter of 1.0 μm, a Ni powder having an average particle diameter of 2.4 μm, and a Co powder having an average particle diameter of 1.9 μm were adjusted at the ratios shown in Table 1. The mixed powder was wet-mixed with IPA using a stainless steel ball mill and cemented carbide balls, added with 3% by weight of paraffin, mixed, pressed into CNMG120408 at 200 MPa, and fired under the firing conditions shown in Table 1. When the temperature was lowered, He gas was injected in an amount shown in Table 1.

The obtained cermet was processed with a diamond grindstone, and the cutting performance was evaluated under the following conditions. In addition, each sample was observed with a scanning electron microscope (SEM), and image analysis was performed in a 7 mm × 7 mm area using commercially available image analysis software for five arbitrary photographs at a magnification of 7000 × to obtain a hard phase (first hard phase). , The second hard phase) was confirmed. The results are shown in Table 2.
(Cutting conditions)
Cutting evaluation 1
Cutting method: Turning Continuous cutting (Abrasion resistance evaluation)
Cutting speed: 230 m / min
Feeding: 0.25mm / rev
Cutting depth: 2.0mm
Work material: SCM435
Cutting state: wet (emulsion)
Cutting time: 10 minutes Evaluation item: Flank wear width (mm)
Cutting evaluation 2
Cutting method: Turning Interrupted cutting (Evaluation of fracture resistance)
Work Material: S45C, 4-Groove Round Bar Cutting Speed: 100m / min
Feeding and cutting time: After cutting at 0.1 mm / rev for 10 seconds, feed is increased by 0.05 mm / rev and cut for 10 seconds each (up to a maximum feed of 0.5 mm / rev)
Cutting depth: 2mm
Evaluation item: Total cutting time until chipping Cutting state: Wet (emulsion)

  From Tables 1 and 2, Sample No. 1 to 12 showed excellent results in both wear resistance and fracture resistance. On the other hand, sample No. fired with a simple firing pattern. In No. 13, a predetermined surface area was not formed on the surface, and both wear resistance and fracture resistance were reduced. In addition, the sample No. 1 in which the firing temperature C exceeded 1600 ° C. and a large amount of inert gas was introduced when the temperature was lowered. 14 and Sample No. with a TiCN raw material particle size exceeding 1.2 μm. In No. 15, the average particle size of the first or second hard phase exceeded the predetermined range for both the internal and surface regions, and the fracture resistance decreased. Further, the sample heating rate B was slower than 4 ° C./min, the firing temperature C exceeded 1600 ° C., and no inert gas was introduced when the temperature was lowered. In No. 16, the area ratio of the 1st hard phase decreased in the inside, and the fracture resistance decreased. In addition, sample No. 1 with a heating rate faster than 14 ° C./min and a firing temperature C lower than 1500 ° C. In No. 17, the particle size of the second hard phase in the surface portion was small, and the proportion of the first hard phase in the surface portion was large, and the wear resistance was lowered. In addition, the sample No. 1 was heated up to the firing temperature A at 5 ° C./min. In No. 18, the area ratio of the first hard phase in the interior and the surface was too large, and the wear resistance was lowered. Furthermore, the sample No. No. 2 having a heating rate A lower than 0.7 ° C./min and a firing temperature C higher than 1600 ° C. In No. 19, since the particle size of the first hard phase on the surface was large and the particle size of the second hard phase was small, the wear resistance decreased.

It is a copy figure of the scanning electron micrograph about the inside of the TiCN base cermet of the present invention. It is a copy figure of the scanning electron micrograph about the surface vicinity of the TiCN base cermet of this invention.

Explanation of symbols

1: TiCN-based cermet 2: Hard phase 3: Bonded phase 4: Core part 5: Peripheral part

Claims (1)

A hard phase in which TiCN and at least one of carbide, nitride, and carbonitride of at least one metal selected from W, Mo, Cr, Nb, Ta, Zr and V are solid-solved,
A TiCN-based cermet bonded with 1 to 30% by weight of a Co and / or Ni bonded phase,
80% by weight or more of Ti as a metal component, the total amount of at least one metal selected from W, Mo, Cr, Nb, Ta, Zr and V is 1 to 15% by weight, Co and / or Ni A first hard phase in which the total amount of binder phase metal is 0 to 3% by weight ;
Ti is 30 to 70% by weight, and the total amount of at least one metal selected from the above W, Mo, Cr, Nb, Ta, Zr and V is 70 to 30% by weight, Co and / or Ni binder phase The total amount of metal consists of a second hard phase consisting of 0 to 3% by weight ,
In the scanning electron micrograph (SEM) of the TiCN-based cermet arbitrary cross section,
The first hard phase is relatively blacker than the second hard phase,
The second hard phase is observed to be relatively grayish white than the first hard phase,
The hard phase has a double-core structure in which the first hard phase is a core part and the second hard phase is a peripheral part (however, not all of the hard phases have a core structure). )
The average particle diameter d _1in of the first hard phase inside the cermet is 0.05 to 0.5 μm, the area ratio S _1in of the first hard phase occupying the whole inside of the cermet is 40 to 80 area%, and The average particle diameter d _2in of the second hard phase inside the cermet is 0.6-2 μm,
The area ratio S _2in of the second hard phase occupying the entire interior of the cermet is 5 to 40% by area,
The average particle size _{d 1SF} of definitive cermet surface portion of the first hard phase is larger than _{d 1in} in 0.3～1Myuemu,
The area ratio _{S 1SF} of the first hard phase in the total of the cermet surface portion is from 5 to 40 area%, and the average particle diameter _{d 2SF} of the second hard phase in the cermet surface portion 1 to 3 [mu] m _{d 2in} Bigger,
A TiCN-based cermet characterized in that a surface portion region having a thickness of 20 to 100 μm exists in which the area ratio _S2sf of the second hard phase occupying the entire surface portion of the cermet is 50 to 80 area%.

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