JP5127264B2 - 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 Patent Document 1, the hard phase is in a solid solution state, specifically, a hard core having a cored structure with a black core. It is disclosed that by optimizing the existence ratio of the phase and the hard phase having a core structure with a white core, and the particle size thereof, it is possible to improve the excellent durability against thermal shock generated by high-speed cutting, etc. ing.
JP-A-8-199283

  However, even with the cermet disclosed in Patent Document 1, the durability against thermal shock is still insufficient, and there is a limit to the improvement of cutting performance, and further improvement of thermal shock resistance and improvement of fracture resistance and wear resistance. Was demanded.

  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 hardness maintenance and 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 are improved, and the wear resistance of the cermet can be maintained.

That is, the TiCN-based cermet of the present invention includes TiCN and a periodic table IVa other than Ti,
1-30 wt% of a hard phase comprising at least one carbide, nitride and carbonitride of at least one metal selected from Group Va and VIa metals, at least one binder phase of Co and Ni A TiCN-based cermet formed by bonding in a scanning electron microscope (SEM) photograph of an arbitrary cross section of the TiCN-based cermet, wherein the hard phase contains at least 80 wt% Ti as a metal component And 30 to 70% by weight of Ti as a metal component, 70 to 30% by weight of the total amount of at least one metal selected from metals of Group IVa, Va and VIa other than Ti, and Co and Ni The second hard phase is composed of a total amount of binder phase metal of 0 to 3% by weight,
With the area ratio S _1ss depth 5μm less polar surface area of 80 area% or more of the first hard phase in the surface of the cermet is present, then there is a surface area inside the polar surface area, the polar When the range from the surface region to the depth of 20 μm is the surface region, and the inside of the surface region is the inside,
The average particle diameter d _1in of the first hard phase in the inside is 0.05 to _1.5 μm, and the area ratio S _1in of the first hard phase occupying the whole inside is 50 to 70 area%,
The ratio between the average particle diameter _{d 1in} the first hard phase in the inner and the average particle diameter _{d 1SF} of the first hard phase in the surface region _(d 1sf _/ d _1in) is 1.1 to 3, the surface area the ratio between the area ratio _{S 1in} of the first hard phase _(S 1sf _/ S _1in) consists 0.3-0.7 in the inner and the area ratio _{S 1SF} of the first hard phase occupying the,
The ratio S _2sf / S _2in between the area ratio S _2sf of the second hard phase in the surface region sf and the area ratio S _2in of the second hard phase in the interior is 1.5 to 4. Is.

Here, in the above configuration, the ratio _{d 2sf / d 2in} the average particle diameter _{d 2in} the second hard phase in the interior of the average particle diameter _{d 2SF} and the cermet put that before Symbol second hard phase in the surface region sf There characterized by 1.5 to 1.7 der Rukoto.

Moreover, in the said structure, the average particle diameter _d1in of the 1st hard phase in the said cermet is 0.05-1.5 micrometers, and the area ratio _S1in of the 1st hard phase which occupies this cermet inside is 40-80 area%. It is characterized by being.

Furthermore, in the said structure, while the said 1st hard phase contains 80 weight% or more of Ti as a metal component, the said 2nd hard phase is 30 to 70 weight% of Ti as a metal component, periodic table IVa other than Ti, Total amount of at least one metal selected from group metals Va and VIa
There 70-30 wt%, the total amount of binding phase metal of Co and / or Ni is formed of a rate of 0-3% by weight, it is important in that it can maintain the toughness while increasing the hardness of the cermet.

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

  FIG. 1A is a scanning electron microscope (SEM) photograph of an arbitrary cross section including the surface of the TiCN-based cermet of the present invention (hereinafter simply referred to as cermet), and an SEM photograph of an internal arbitrary cross section. This will be described with reference to FIG.

  According to FIG. 1, the TiCN-based cermet (hereinafter simply referred to as cermet) 1 of the present invention is at least one selected from TiCN and Periodic Tables IVa, Va and VIa metals other than Ti. The hard phase 2 formed by dissolving at least one of metal carbide, nitride, and carbonitride is a structure in which the hard phase 2 is bonded with a binder phase 3 of 1 to 30% by weight of Co and / or Ni. According to FIG. 1, the hard phase 2 consists of a black first hard phase 2a and an off-white second hard phase 2b. According to the present invention, the inside of the cermet 1 (FIG. 1 (b)) There is a surface region sf (FIG. 1A) composed of different tissues.

According to FIG. 1, the average particle diameter d _1in of the first hard phase 2a in the cermet 1 (FIG. 1 (b): in) is 0.05 to _1.5 μm, and the first hard phase 2a is in the cermet 1. The area ratio S _1in occupies 40 to 80 area%, the average particle diameter d _1sf of the first hard phase 2a on the surface of the cermet 1 (FIG. 1 (a)), and the first hard phase 2a inside the cermet 1 the ratio between the average particle diameter _{d 1in (d 1sf / d 1in} ) is 1.1 to 3, the area ratio of the first hard phase occupying the cermet 1 surface portion _{S 1SF} and the area ratio of the first hard phase occupies the internal cermet surface area ratio of the _{S 1in (S 1sf / S 1in} ) consists of 0.3 to 0.7 (Fig. 1 (a): sf) is present.

  As a result, the strength of the cermet 1 can be increased, and the thermal conductivity and Young's modulus can be increased while maintaining the hardness of the surface of the cermet 1, thereby improving the thermal shock resistance on the surface of the cermet 1. The wear resistance and fracture resistance of the cermet 1 can be improved even under conditions that cause severe thermal shock such as feed cutting and wet cutting.

Incidentally, the average particle size _(d 1, _{d 2)} and the area ratio _(S 1, _{S 2),} for scanning electron microscope (SEM) photograph can be measured by using a commercially available image analyzer.

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 tends to decrease. On the other hand, when d _1in exceeds 0.5 μm, the strength and hardness of the cermet 1 are lowered, and both the chipping resistance and the wear resistance tend to be 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 50 area% or more than 70 area%, the strength and hardness of the cermet 1 are lowered. Range of S _1in is 50-70 area%.

Further, the average particle diameter d2in of the second hard phase 2b in the cermet 1 is desirably 0.6 μm to ₂ μm from the viewpoint of improving the strength by making the dispersed state of the second hard phase 2b good. A more desirable range of d _2in is 0.8 to 1.5 μm.

Further, the area ratio _S2in of the second hard phase 2b occupying the cermet 1 is 5 to 40% by area, so that the particles of the cermet 1 can be sufficiently sintered while being fine and the strength is improved. Is desirable. A more desirable range of the area ratio _S2in is 10 to 30 area%.

On the other hand, in the surface region sf of the cermet 1, the ratio of the average particle diameter _{d 1in} the first hard phase 2a in the average particle diameter _{d 1SF} and the cermet 1 inside the first hard phase 2a in the cermet 1 surface _{(d 1sf} / _{d 1in)} is small and will heat conductivity and plastic deformation resistance is lower than 1.1, conversely, the hardness decreases at greater cermets 1 surface than the ratio _{(d 1sf /} d _1in) 3 Therefore, the wear resistance tends to decrease. The average particle diameter d _2sf of the second hard phase 2b in the cermet 1 surface region is 1 μm to 3 _μm in terms of maintaining the thermal conductivity and plastic deformation resistance of the cermet 1 surface and increasing the fracture resistance. desirable. A desirable range of d _2sf is 1.2 to 2 μm.

In addition, it is _desirable that the area ratio S _1sf of the first hard phase 2a in the cermet 1 surface region sf is 5% by area to 40% by area in terms of improving the thermal conductivity and plastic deformability of the cermet 1 surface. A desirable range of S _1sf is 7 to 25 area%.

The ratio between the area ratio _{S 1in} of the first hard phase occupying the cermet inside the area ratio _{S 1SF} of the first hard phase occupying the cermet 1 surface area sf _(S 1sf _/ S _1in) is as shown in FIG. 2 0 If it is smaller than .3, the thermal conductivity and plastic deformation resistance of the cermet 1 are lowered. Conversely, if it exceeds 0.7, the fracture resistance of the cermet 1 surface tends to be lowered due to the lack of the first hard phase and the binder phase. . The ratio of the area ratio _{(S 1sf /} S _1in) is 1.1 to 2, and is preferably 1.2 to 1.8.

The area ratio _S2sf of the second hard phase 2b is preferably 50 to 80 area%, particularly 60 to 75 area%, from the _viewpoint of _fracture resistance and wear resistance of the cermet 1 surface.

  Furthermore, according to the present invention, the white portion 2c is present at the center of the grayish white second hard phase 2b, and the proportion of the white portion 2c in the cermet 1 (FIG. 1B) is the surface of the cermet 1 (see FIG. 1 (a)) is larger than the abundance of the white portion 2c, the hard phase 2 (2a, 2b) inside the cermet 1 is atomized to increase the strength of the cermet 1 and the hard phase 2 (2a on the surface of the cermet 1). 2b) is preferable in terms of improving the thermal shock resistance of the cermet 1 by optimizing the solid solution state.

  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 periodic table IVa, Va and VIa group metals other than Ti. The total amount of at least one metal selected from among them, particularly one or more of W, Mo, Cr, Nb and V, and further containing W as an essential component (referred to as a solid solution metal in the present invention) is 1 to 15 weights. %, And the total amount of at least one binder phase metal of Co and Ni is preferably 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 2sf / d 2in = 1.5~1.7} , S 2sf / S 2in = 1.5 It is desirable to be ~ 4.

Further, in order to achieve both fracture resistance and wear resistance of the cermet 1, the thickness of the surface region sf is preferably 20 to 100 μm, particularly preferably 30 to 50 μm. Further, the wear resistance of the cermet 1 is maintained by the presence of the pole surface region ss having the area ratio S _1s of the first hard phase 2a of 80 area% or more on the pole surface located further on the surface portion of the surface region sf. It is important in that it can be done.

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

  Moreover, according to the present invention, a hard coating layer may be separately formed on the surface of the cermet 1.

(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. Since the TiCN raw material powder forms a cored structure of the first hard phase and the second hard phase by sintering together with other solid solution metal raw materials, the average particle size of the first hard phase 2a is the same as that of the TiCN raw material powder. It tends to be smaller than the average particle size.

  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 made of a carbide of at least one metal selected from TiCN powder having an average particle size of 0.1 to 1.2 μm and metals of groups IVa, Va and VIa other than Ti. After the nitride and carbonitride powders and Co and / or Ni are prepared and processed into a predetermined shape, (a) the temperature is increased to 1150 to 1250 ° C. at a temperature increase rate of 0.7 to 2 ° C./min. Then, (b) the temperature is raised to 1400-1500 ° C. at a temperature increase rate of 5-15 ° C./min, and (c) the temperature is increased to 1500-1600 ° C. at a temperature increase rate of 4-14 ° C./min. In addition, in the temperature raising step (b) (c), nitrogen gas or an inert gas is filled so as to have an atmosphere of 10 to 150 Pa , maintained at the maximum temperature in the temperature raising step (c) for a predetermined time, To do.

  According to the present invention, the cermet having the above-described structure can be produced by lowering the temperature in a state where the temperature rise rate during the firing and a predetermined amount of inert gas is filled when the temperature is lowered.

TiCN powder with an average particle diameter of 0.7 μm or 2 μm, TiN powder with an average particle diameter of 1.5 μm, TaC powder with an average particle diameter of 2 μm, NbC powder with an average particle diameter of 1.5 μm, average particle A WC powder having a diameter 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 are shown. The mixed powder adjusted in the ratio shown in 1 was wet mixed with isopropyl alcohol (IPA) using a stainless steel ball mill and cemented carbide balls, 3% by weight of paraffin was added and mixed, and then press molded into CNMG120408 at 200 MPa. And firing under the firing conditions shown in Table 1. In the temperature raising steps (b) and (c), N ₂ 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 an area of 7 μm × 7 μm using a commercially available image analysis software for arbitrary five places of 7000 × photographs to obtain a hard phase (first The existence state of the hard phase and 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
Work material: Round bar with 4 grooves Cutting speed: 100m / min
Feeding and cutting time: After cutting for 10 seconds at 0.1 mm / rev, 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. In 1-4, the result which was excellent in both abrasion resistance and defect resistance was shown. On the other hand, sample No. fired with a simple firing pattern. In No. 5, a predetermined surface area was not formed on the surface, and both wear resistance and fracture resistance were reduced. Sample No. using TiCN powder having an average particle diameter of 2 μm as a raw material. In _No. 6, the average particle diameter d _1in of the hard particles inside the sintered body exceeded 1.5 μm, and the hardness and strength decreased. As a result, tool wear progressed early. Furthermore, in the temperature rising step B, the heating rate is lower than 4 ° C., and the sample No. In 7 the ratio of the average particle diameter _{d 1in} the first hard phase _{(d 1sf /} d _1in) was intended reduced wear severe than 1.1. Furthermore, sample No. No. in which the heating rate A was slower than 0.7 ° C./min and no inert gas was introduced in the heating steps b and c. In 8 ratio between the average particle diameter _{d 1in} the first hard phase _{(d 1sf /} d _1in) has drops significantly wear resistance than 3.

It is a scanning electron micrograph about (a) surface and (b) inside of TiCN base cermet of the present invention. It is a scanning electron micrograph about (a) surface and (b) inside of the conventional TiCN base cermet.

Explanation of symbols

1: TiCN-based cermet 2: hard phase 2a: first hard phase 2b: second hard phase 3: bonded phase in: inside of cermet sf: cermet surface area ss: cermet pole surface area

Claims (2)

A hard phase comprising TiCN and at least one of carbides, nitrides and carbonitrides of at least one metal selected from metals of Group IVa, Va and VIa of the periodic table other than Ti, Co and Ni A TiCN-based cermet bonded with 1 to 30% by weight of at least one bonded phase, wherein the hard phase is Ti as a metal component in a scanning electron microscope (SEM) photograph of an arbitrary cross section of the TiCN-based cermet. The total amount of at least one metal selected from the group consisting of metals in the periodic table IVa, Va and VIa other than Ti as the first hard phase containing at least 80% by weight and 30 to 70% by weight of Ti as the metal component Comprising a second hard phase consisting of 70 to 30% by weight and a total amount of Co and Ni binder phase metals of 0 to 3% by weight,
With the area ratio S _1ss depth 5μm less polar surface area of 80 area% or more of the first hard phase in the surface of the cermet is present, then there is a surface area inside the polar surface area, the polar When the range from the surface region to the depth of 20 μm is the surface region, and the inside of the surface region is the inside,
The average particle diameter d _1in of the first hard phase in the inside is 0.05 to _1.5 μm, and the area ratio S _1in of the first hard phase occupying the whole inside is 50 to 70 area%,
The ratio between the average particle diameter _{d 1in} the first hard phase in the inner and the average particle diameter _{d 1SF} of the first hard phase in the surface region _(d 1sf _/ d _1in) is 1.1 to 3, the surface area the ratio between the area ratio _{S 1in} of the first hard phase _(S 1sf _/ S _1in) consists 0.3-0.7 in the inner and the area ratio _{S 1SF} of the first hard phase occupying the,
The ratio S _2sf / S _2in between the area ratio S _2sf of the second hard phase in the surface region sf and the area ratio S _2in of the second hard phase in the interior is 1.5 to 4. TiCN-based cermet. The ratio d _2sf / d _2in between the average particle diameter d _2sf of the second hard phase in the surface region sf and the average particle diameter d _2in of the second hard phase inside the cermet is 1.5 to 1.7. The TiCN-based cermet according to claim 1.

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