JP2017186624A - Hard metal alloy and manufacturing method therefor and carbide tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hard metal alloy having high hardness and high deflective strength, excellent in fracture toughness and having enhanced oxidation resistance and corrosion resistance by achieving improvement of properties thereof.SOLUTION: A hard metal alloy has a hard phase mainly containing WC, a binding phase mainly containing at least one kind selected from a group consisting of Co, Ni and Fe and a dispersion phase consisting of fine particles of titanium-based carbonitride represented by general formula (1) and having a particle diameter generated by dispersion in the binding phase of 50-300 nm. (Ti,W)(C,N) (1), where X is 0.2-0.6 and Y is 0.2-0.6. At least a part of fine particles 3 of the titanium-based carbonitride generated by dispersion in the binding phase 2 adheres to a surface of WC particles 1 and fine irregularity 4 is formed on the surface of the WC particles.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a cemented carbide and a method for manufacturing the same, and further to a cemented carbide tool using the cemented carbide, and in particular, a tungsten carbide-based superalloy that has improved mechanical properties such as hardness, bending strength, and fracture toughness. The present invention relates to a hard alloy and a manufacturing method thereof.

  2. Description of the Related Art Conventionally, a cutting tool has been used to perform processing such as cutting on various metal materials such as steel and cast iron and other workpieces. In this type of cutting tool, it is desired to maintain excellent finished surface accuracy over a long period of use and to exhibit stable cutting performance. In order to satisfy such a demand, a WC-based cemented carbide obtained by liquid phase sintering of tungsten carbide (WC) fine particles with Co is widely used as a material having high hardness while having high hardness. .

  In this type of WC-based cemented carbide, when the growth of the WC particles constituting the hard phase proceeds in the sintering process, the WC particles are coarsened and mechanical properties such as hardness and bending strength are reduced. In order to improve such a problem, a cemented carbide has been proposed in which grain growth of WC particles is suppressed, WC particles having a fine particle diameter are formed, and mechanical properties are improved (Non-Patent Document). 1).

In Non-Patent Document 1, in WC-Co ultrafine cemented carbide, by adding Ti (C, N) that does not dissolve in the Co phase, it is possible to realize grain growth suppression of WC particles during liquid phase sintering. Is described. Further, in Non-Patent Document 1, sintering is performed using a raw material powder in which a predetermined amount of Ti (C, N) and Cr ₃ C ₂ powders are added to a mixed powder obtained by mixing WC powder and Co powder. Further, it is disclosed that WC-Co ultrafine cemented carbide can obtain high bending strength with high hardness.

Naoyuki Takada, Yoshihiro Mori, Satoshi Matsuda, Hideaki Matsubara, “On the ultrafine grain alloying of WC-based cemented carbide by the pinning effect of Ti (C, N) fine particles”, Powder Powder Metallurgy Association, 2015 Spring Meeting, Meeting Summary p.25

  By the way, a cemented carbide used for a cemented carbide tool such as a cutting tool is desired not only to have a high hardness and a high bending strength but also to be excellent in fracture toughness. Furthermore, it is desired that cemented carbides used for cemented carbide tools are excellent in oxidation resistance and corrosion resistance.

  Therefore, an object of the present invention is to provide a cemented carbide having high hardness and high bending strength, excellent fracture toughness, and excellent oxidation resistance and corrosion resistance, and a method for producing the same.

  A further object of the present invention is to provide a cemented carbide tool such as a cutting tool that can maintain excellent finished surface accuracy over a long period of use and can exhibit stable cutting performance.

  The inventors have determined that the hardness, resistance, and resistance of a cemented carbide having a hard phase mainly composed of tungsten carbide (WC) and a binder phase mainly composed of at least one selected from the group consisting of Co, Ni and Fe. The present invention has been completed as a result of diligent research aimed at improving bending strength, fracture toughness, and the like.

That is, in the present invention, a hard phase mainly composed of tungsten carbide (WC), a binder phase mainly composed of at least one selected from the group consisting of Co, Ni, and Fe, and dispersedly formed in the binder phase. A dispersed phase composed of fine particles of titanium-based carbonitride represented by the following general formula (1) having a particle size of 50 to 300 nm,
(Ti _1-X , W _X ) (C _1-Y , N _Y ) (1)
(In the formula, X is 0.2 to 0.6, and Y is 0.2 to 0.6.)
At least a part of the fine particles of the titanium-based carbonitride dispersed and formed in the binder phase adheres to the surface of the WC particles constituting the hard phase, and fine irregularities are formed on the surface of the WC particles. It is characterized by that.

  The cemented carbide according to the present invention comprises 5 to 30% by weight of a binder phase and 0.15 to 15% by weight of a dispersed phase with respect to the total weight. The balance contains a hard phase and inevitable impurities. The dispersed phase is contained in a proportion of 3 to 50% by weight with respect to the binder phase.

  In the present invention, a part of W constituting the carbonitride may be replaced with at least one selected from the group consisting of Ta, Nb, Mo, Zr, Hf, Cr, and V. .

  Furthermore, this invention is the cemented carbide tool formed using the cemented carbide mentioned above.

  The present invention is also a method for producing a cemented carbide, first selected from the group consisting of a powder mainly composed of tungsten carbide (WC) constituting the hard phase and Co, Ni and Fe constituting the binder phase. And at least one selected from (Ti, W) C, (Ti, W) (C, N), TiC, TiN, and Ti (C, N) constituting the dispersed phase. A raw material powder prepared by mixing a powder made of a seed Ti compound is compression-molded into a predetermined shape to produce a compression-molded body.

  Next, the compression molded body is heated to 600 to 900 ° C. in a heating furnace having a vacuum atmosphere or an inert atmosphere to prepare a pre-sintered body.

  Thereafter, the pre-sintered body is heated to about 1000 ° C. in a weakly oxidizing atmosphere to oxidize the Ti compound mixed in the raw material powder, and then the oxidized Ti compound is contained in the raw material powder. To reduce and carbonize to produce Ti carbonate or Ti double carbonate.

  Next, the pre-sintered body is heated to about 1000 ° C. or more in a nitrogen atmosphere and subjected to nitriding treatment, and the Ti carbonate or Ti double carbonate generated in the reduction and carbonization steps is reduced and nitrided. (C, N) or Ti double carbonitride is produced.

  Next, the pre-sintered body is heat-treated at 1350-1500 ° C. for 60 to 120 minutes, which is a temperature equal to or higher than the liquid phase temperature at which the metal constituting the binder phase melts to form a liquid phase. The cemented carbide is obtained.

And in the process of producing | generating the said sintered compact, WC contained in the said compression molding body is diffused in the said Ti (C, N) or Ti double carbonitride, and the following general formula which makes a particle size 50-300 nm A dispersed phase composed of fine titanium-carbonitride particles represented by (1) is dispersedly formed in the binder phase.
(Ti _1-X , W _X ) (C _1-Y , N _Y ) (1)
(In the formula, X is 0.2 to 0.6, and Y is 0.2 to 0.6.)
At this time, at least a part of the fine particles of titanium-based carbonitride constituting the dispersed phase adhere to the surface of the WC particles constituting the hard phase and form fine irregularities on the surface of the WC particles.

In the present invention method, when using TiO ₂ as a Ti compound, so as to generate a Ti carbonate the by C contained in the immediately the raw material powder of TiO ₂ contained in the raw material powder reduced by carbonizing May be.

  In the method of the present invention, fine particles of titanium-based carbonitride are WC to Ti (C, N) produced by nitriding a Ti carbonate or Ti double carbonate produced by reducing and carbonizing a Ti compound. Those produced by diffusing can be used.

  In the method of the present invention, the Ti compound constituting the dispersed phase mixed with the raw material powder is desirably added in a range of 2 to 20% by weight in terms of TiC with respect to the metal powder constituting the binder phase.

  In the cemented carbide according to the present invention, fine titanium-based carbonitride fine particles are dispersed and formed in the binder phase, and a part of the fine particles adheres to the surface of the WC particles, thereby suppressing grain growth of the WC particles. , Fine irregularities are formed on the surface of the WC particles. The cemented carbide according to the present invention has improved adhesion to the hard phase of the binder phase, excellent fracture toughness, desired hardness and bending strength, and excellent oxidation resistance and corrosion resistance. Has characteristics.

  The cemented carbide tool according to the present invention is formed of a cemented carbide having improved hardness, bending strength, and fracture toughness, so that excellent finished surface accuracy can be maintained over a long period of use and stable. Cutting performance can be exhibited.

  By adopting the method according to the present invention, it is possible to produce a cemented carbide in which the growth of WC particles is suppressed during sintering.

It is a scanning electron micrograph which shows an example of the cross-sectional structure | tissue which shows the state in which the fine particle of (Ti, W) (C, N) was produced | generated in the binder phase of the cemented carbide which concerns on Example 1 of this invention. In the cemented carbide alloy which concerns on Example 1 of this invention, it is a scanning electron micrograph which shows an example of the state in which the fine unevenness | corrugation is formed in the surface of the WC particle which comprises a hard phase. It is a scanning electron micrograph which shows an example of the cross-sectional structure | tissue which shows the state in which the fine particle of (Ti, W) (C, N) was produced | generated in the binder phase of the cemented carbide which concerns on Example 2 of this invention. In the cemented carbide alloy which concerns on Example 2 of this invention, it is a scanning electron micrograph which shows an example of the state with which the fine unevenness | corrugation is formed in the surface of the WC particle which comprises a hard phase. It is a scanning electron micrograph which shows an example of the cross-sectional structure | tissue which shows the state in which the fine particle of (Ti, W) (C, N) was produced | generated in the binder phase of the cemented carbide alloy which concerns on Example 3 of this invention. In the cemented carbide alloy which concerns on Example 3 of this invention, it is a scanning electron micrograph which shows an example of the state in which the fine unevenness | corrugation is formed in the surface of the WC particle which comprises a hard phase. It is a scanning electron micrograph which shows an example of the cross-sectional structure | tissue which shows the state in which the fine particle of (Ti, W) (C, N) was produced | generated in the binder phase of the cemented carbide alloy which concerns on Example 4 of this invention. In the cemented carbide alloy which concerns on Example 4 of this invention, it is a scanning electron micrograph which shows an example of the state in which the fine unevenness | corrugation is formed in the surface of the WC particle which comprises a hard phase. It is a scanning electron micrograph which shows an example of the cross-sectional structure | tissue which shows the state in which the fine particle of (Ti, W) (C, N) was produced | generated in the binder phase of the cemented carbide which concerns on Example 5 of this invention. In the cemented carbide alloy which concerns on Example 5 of this invention, it is a scanning electron micrograph which shows an example of the state in which the fine unevenness | corrugation is formed in the surface of the WC particle which comprises a hard phase.

  The cemented carbide according to the present embodiment includes at least one selected from a hard phase mainly composed of WC particles and Co, Ni, Co—Ni alloy, Co—Fe alloy, and Fe—Ni alloy, or these metals. Co-W alloy, Ni-Cr alloy, Co-Cr-V alloy, Co-Ni-Cr alloy, Co-Ni-, which is a solid solution of at least one of W and Cr, Mo and V of 20 wt% or less A binder phase containing at least one of W-Cr alloy and Fe-Ni-Co-W-Cr-Mo alloy, and a dispersed phase composed of fine particles of titanium-based carbonitride dispersed in the binder phase; It is composed of

  In this cemented carbide, the binder phase is desirably 5% by weight or more based on the total weight in order to maintain the strength and toughness of the cemented carbide, and 30% based on the total weight in order to maintain the hardness of the cemented carbide. It is desirable that the amount is not more than% by weight. The dispersed phase is preferably contained in the range of 0.15 to 15% by weight with respect to the total weight in order to adhere to the surface of the WC particle and form fine irregularities on the surface of the WC particle. When the dispersed phase is contained in an amount of 15% by weight or more with respect to the total weight of the cemented carbide, the dispersed phase is aggregated to inhibit the fine irregularities formed on the surface of the WC particles. This dispersed phase is contained in the range of 3 to 50% by weight with respect to the binder phase. Note that the balance of the cemented carbide includes WC and inevitable impurities constituting the hard phase.

  And the hard phase is comprised with the WC powder which makes a particle size 0.5-30 micrometers. The binder phase was a solid solution of at least one selected from Co, Ni, Co—Ni alloy, and Fe—Ni alloy, or at least one of these metals, and 20 wt% or less of W, Cr, Mo, and V. Any one of Co-W alloy, Co-Cr alloy, Co-Cr-V alloy, Co-Ni-Cr alloy, Co-Ni-W-Cr alloy, Fe-Ni-Co-W-Cr-Mo alloy It is comprised with the metal containing the above.

The cemented carbide according to the present embodiment has a dispersed phase composed of fine particles of titanium-based carbonitride dispersed in a binder phase. This dispersed phase is a titanium-based carbonitride represented by the following general formula (1), and is composed of fine particles having a particle size of 50 to 300 nm or less.
(Ti _1-X , W _X ) (C _1-Y , N _Y ) (1)
(In the formula, X is 0.2 to 0.6, and Y is 0.2 to 0.6.)
The fine particles of titanium-based carbonitride represented by the above formula (1) are generated in the binder phase, and at least a part of the fine particles adheres to the surface of the WC particles constituting the hard phase, and the fine particles are formed on the surface of the WC particles. Unevenness is formed.

  In the cemented carbide according to the present embodiment, the portion of the WC particles to which the fine particles of titanium carbonitride are attached is inhibited from grain growth during the sintering process, and grain growth is suppressed. By suppressing the grain growth of the WC particles, the WC particles can maintain the initial particle size, and a cemented carbide having the intended mechanical properties can be obtained.

  Furthermore, in the cemented carbide according to the present embodiment, fine irregularities are formed on the surface of the WC particles, and the surface area of the WC particles is increased, thereby improving the adhesion between the WC particles and the binding metal constituting the binder phase. To do. Furthermore, it is determined that the surface area of the WC particles increases, the thickness of the bonding metal that bonds the WC particles decreases, and the hardness of the cemented carbide increases.

  Thus, in the cemented carbide according to the present embodiment, fine titanium-based carbonitride fine particles are dispersed and generated in the binder phase, and a part of the fine particles adheres to the surface of the WC particles. As a result, fine irregularities are formed on the surface of the WC particles, and grain growth of the WC particles is suppressed. As a result, the cemented carbide according to the present embodiment has improved adhesion to the hard phase of the binder phase, excellent fracture toughness, desired hardness and bending strength, and further has oxidation resistance and corrosion resistance. It has excellent characteristics.

  In addition, the cemented carbide according to the present embodiment, a part of W constituting the titanium-based carbonitride constituting the fine particles dispersed and generated in the binder phase, Ta, Nb, Mo, Zr, Hf, It may be replaced with at least one selected from the group consisting of Cr and V. A metal material to be replaced with a part of W is added in advance to the raw material powder. The replacement of a part of W by the metal is performed during the process of sintering the cemented carbide according to the present embodiment.

  The cemented carbide according to the present embodiment described above is processed into a cemented carbide tool such as a cutting tool. This cemented carbide tool is manufactured using a cemented carbide according to the present embodiment as a base material and employing a known manufacturing method.

Next, a method for manufacturing the cemented carbide according to the present embodiment will be described.
First, raw material powder necessary for manufacturing the cemented carbide according to the present embodiment is prepared. This raw material powder is composed of a metal powder constituting a hard phase, a metal powder constituting a binder phase, and a metal powder constituting a dispersed phase.

As the metal powder constituting the hard phase, WC powder having a particle size (average particle size) of 0.5 to 30 μm is used. As the metal powder constituting the binder phase, a metal powder mainly composed of at least one selected from the group consisting of Co, Ni and Fe is used. You may make it add at least 1 sort (s) selected from the group which consists of Ta, Nb, Mo, Zr, Hf, Cr, and V further to the metal powder which comprises a binder phase. As the metal powder constituting the binder phase, one having a particle size (average particle size) of 0.5 to 3 μm is used. The metal powder constituting the dispersed phase is at least one selected from (Ti, W) C, (Ti, W) (C, N), TiC, TiN, Ti (C, N), and TiO _2. The powder which consists of Ti compound containing is used. The Ti compound powder used here has a particle size (average particle size) of 0.5 to 3.0 μm. As these metal powders, commercially available products can be used.

  As the Ti compound, it is desirable to use a powder having a smaller particle diameter so that a titanium-based carbonitride having a smaller particle diameter is produced, and a Ti compound having a particle diameter of 0.5 to 1.0 μm is used.

  And raw material powder contains 5-30 weight% of the metal powder which comprises a binder phase, contains 2-20 weight% of Ti compounds which comprise a dispersed phase in conversion of TiC, and comprises a hard phase in the remainder. It is composed of WC powder and inevitable impurities.

  The raw material powder is mixed using an attritor or a rolling ball mill. By mixing the raw material powder, the respective materials are uniformly mixed.

  An oil and fat component such as paraffin wax is added to the raw material powder in consideration of moldability when forming into a predetermined shape.

  The mixed raw material powder is molded into a compression-molded body having a predetermined shape using a molding method such as a dry pressure molding method, a cold isostatic pressing method, or an injection molding method. This compression molded body is formed into a predetermined shape of a carbide tool such as a cutting tool, for example.

  When a raw material powder to which an oil and fat component such as paraffin wax is added is used, a degreasing treatment is performed on a compression molded body that has been compression molded into a predetermined shape. This degreasing treatment is performed by heating the compression molded body to about 300 to 500 ° C. in a heating furnace having a hydrogen atmosphere, an inert gas atmosphere, or a vacuum atmosphere.

  Next, the compression molded body subjected to the degreasing treatment is pre-sintered at a temperature of about 600 to 900 ° C. in a heating furnace having a vacuum atmosphere or an inert gas atmosphere to obtain a pre-sintered body. If necessary, the pre-sintered body is machined into a desired tool shape such as a cutting tool.

  The pre-sintered body obtained by pre-sintering the compression-molded body is a cemented carbide as a sintered body through the main sintering step. The main sintering of the pre-sintered body is performed through the following steps.

  In the present embodiment, in order to perform the main sintering of the pre-sintered body, first, the pre-sintered body is heat-treated in a heating furnace having a weak oxidizing atmosphere until the temperature becomes about 1000 ° C. When the pre-sintered body is heated to about 1000 ° C. in a weak oxidizing atmosphere, the Ti compound mixed in the raw material powder is oxidized. Next, the oxidized Ti compound is reduced by C contained in the raw material powder and further carbonized to produce Ti carbonate or Ti double carbonate.

When TiO ₂ previously oxidized as the Ti compound is used, the pre-sintered body is heat-treated in a vacuum atmosphere to about 1000 ° C. without making the inside of the furnace a weak oxidizing atmosphere, and the oxidation step is performed. Without passing, TiO ₂ may be directly reduced and carbonized by C contained in the raw material powder to produce Ti carbonate.

  Following the process of reducing and carbonizing the Ti compound, the pre-sintered body is nitrided. The nitriding treatment of the pre-sintered body is performed by introducing nitrogen gas into a heating furnace that has been subjected to reduction and carbonization treatment, and the furnace is filled with a nitrogen atmosphere. At this time, the inside of the heating furnace is about 1000 ° C. or higher. The nitrogen pressure in the heating furnace is about 1 kPa. In the heat treatment step of sintering the pre-sintered body in a nitrogen atmosphere, Ti carbonate or Ti double carbonate produced by reducing and carbonizing the Ti compound is reduced, nitrided, and Ti (C, N) or Ti double carbonitride is produced.

  Next, the sintering process which makes a pre-sintered body the cemented carbide as a sintered compact is performed. In this sintering treatment, the pre-sintered body is held for 60 to 120 minutes at a temperature of about 1350 to 1500 ° C. in a temperature range equal to or higher than the liquid phase temperature at which the binder metal constituting the binder phase melts to become a liquid phase. Is done. This sintering process is performed using a sintering furnace. As the sintering furnace, the heating furnace used in the above-described steps may be used.

By the way, in the process in which the pre-sintered body is sintered and the cemented carbide that is the sintered body is created, the Ti (C, N) or Ti double carbonitride generated in the above-described sintering process, WC contained in the sintered body diffuses to produce a titanium-based carbonitride represented by (Ti, W) (C, N). The titanium-based carbonitride generated here (Ti, W) (C, N) is represented by the following general formula (1).
(Ti _1-X , W _X ) (C _1-Y , N _Y ) (1)
(In the formula, X is 0.2 to 0.6, and Y is 0.2 to 0.6.)
The fine particles of titanium-based carbonitride represented by the above formula (1) are generated in the binder phase, and at least a part of the fine particles adheres to the surface of the WC particles constituting the hard phase, and the fine particles are formed on the surface of the WC particles. Form irregularities

  By the way, the Ti compound which is made into (Ti, W) (C, N) through the process of sintering the compression molded body is oxidized in each temperature range described above, and after being reduced and carbonized by C, Nitriding is performed, and then W is diffused into Ti to be dissolved, and then refined. By passing through this sintering treatment step, the Ti compound having a particle size of 0.5 to 3.0 μm is made into fine particles having a particle size of 50 to 300 nm.

  By the method according to the present invention, a dispersed phase composed of fine particles of titanium carbonitride is generated in the binder phase, and at least some of the fine particles of titanium carbonitride constituting the dispersed phase constitute a hard phase. A cemented carbide that adheres to the surface of the WC particles and has fine irregularities formed on the surface of the WC particles is obtained.

  The cemented carbide produced by the manufacturing method according to the present embodiment is such that a part of fine particles made of fine titanium carbonitride dispersed and produced in the binder phase adheres to the surface of the WC particles. Fine irregularities are formed on the surface of the particles to suppress grain growth of the WC particles. As a result, the adhesiveness of the binder phase to the hard phase is improved, the fracture toughness is excellent, the desired hardness and the bending strength, and the oxidation resistance and corrosion resistance are excellent.

  Next, specific examples of the cemented carbide manufactured by the method of the present invention will be described.

[Example 1]
The cemented carbide of Example 1 has a WC powder having a particle size of 1.5 μm constituting a hard phase, a Co powder having a particle size constituting a binder phase of 1.1 μm, and a Ti compound constituting a dispersed phase. It was prepared using a raw material powder mixed with TiO ₂ powder having a thickness of 1.0 μm.

Here, the raw material powder contains 10% by weight of Co powder and 1.3% by weight of TiO ₂ powder, and the balance is composed of WC powder and inevitable impurities.

  This raw material powder is added with an ethanol solvent and pulverized and mixed using a ball mill. The mixed and pulverized raw material powder is taken out from the ball mill and dried. Paraffin wax is added to the pulverized and dried raw material powder in order to improve moldability in the molding process.

  The raw material powder to which the paraffin wax is added is molded into a compression-molded body having a predetermined shape using a dry pressure molding method.

  Next, the compression molded body is heated to about 500 ° C. in a heating furnace having a hydrogen atmosphere, and degreased. The compression molded body that has been subjected to the degreasing treatment is heated to about 900 ° C. and pre-sintered in a heating furnace in a vacuum atmosphere.

  A pre-sintered body obtained by pre-sintering this compression-molded body is sintered through the following sintering process to obtain a cemented carbide as a sintered body.

First, the pre-sintered body is heat-treated in a heating furnace in a vacuum atmosphere until it reaches about 1000 ° C. In this heat treatment step, TiO ₂ mixed in the raw material powder is reduced and carbonized by C contained in the raw material powder to form Ti carbonate.

  Next, following the process of reducing and carbonizing the Ti compound, the pre-sintered body is nitrided. Nitriding treatment of the pre-sintered body is performed by introducing nitrogen gas into a heating furnace subjected to reduction and carbonization treatment. At this time, the nitrogen pressure in the heating furnace is about 1 kPa. Then, the pre-sintered body is heat-treated with the inside of the heating furnace being about 1000 ° C. or higher. The pre-sintered body is heated to about 1000 ° C. or higher in a nitrogen atmosphere, and Ti carbonate produced in the reduction and carbonization steps is reduced and nitrided to produce Ti (C, N) or Ti double carbonitride. To do.

  Next, the temperature inside the heating furnace is further raised, and the pre-sintered body is heated to 1400 ° C., which is equal to or higher than the liquid phase temperature at which the binder metal constituting the binder phase melts to become a liquid phase. The pre-sintered body is held for 120 minutes in a state of being heated to 1400 ° C., thereby forming a cemented carbide that is a sintered body in which the hard phase and the binder phase are sinter-bonded.

  The cemented carbide prepared here was then cooled and used as a test piece. The test piece obtained here is cut at the center. The cut surface of the cut specimen was ground with a diamond grindstone, then mirror-finished with diamond paste, and the structure was observed using a scanning electron microscope. The observation results are shown in FIGS. As shown in FIGS. 1 and 2, a large number of fine particles 3 having a particle size of 50 to 300 nm are dispersed and generated in a binder phase 2 in which WC particles 1 constituting a hard phase are bonded. As shown in FIG. 2, some of these fine particles 3 constituting the dispersed phase adhere to the surface of the WC particles 1 constituting the hard phase, and form fine irregularities 4 on the surface of the WC particles 1 to form the WC particles 1. Suppresses grain growth.

The fine particles 3 produced in the binder phase 2 are analyzed by an energy dispersive X-ray analyzer and are represented by (Ti _0.54 , W _0.46 ) (C _0.75 , N _0.25 ). It was confirmed that this was a titanium-based carbonitride.

[Example 2]
The cemented carbide of Example 2 has a WC powder having a particle size of 1.5 μm constituting the hard phase, a Co powder having a particle size constituting the binder phase of 1.1 μm, and a Ti compound constituting the dispersed phase. It was prepared using a raw material powder mixed with TiO ₂ powder having a thickness of 1.0 μm.

Here, the raw material powder contains 20% by weight of Co powder and 1.3% by weight of TiO ₂ powder, and the remainder is composed of WC powder and inevitable impurities.

  In this example, as in Example 1 described above, the raw material powder is pulverized and mixed, and the pulverized raw material powder is formed into a compression-molded body having a predetermined shape.

  Next, the compression molded body is heated to about 500 ° C. in a heating furnace having a hydrogen atmosphere, and degreased. The compression molded body that has been subjected to the degreasing treatment is heated to about 900 ° C. and pre-sintered in a heating furnace in a vacuum atmosphere.

The pre-sintered pre-sintered body is heat-treated in a heating furnace in a vacuum atmosphere until it reaches about 1000 ° C., and TiO ₂ mixed with the raw material powder is contained in the raw material powder as in Example 1. It is reduced and carbonized by C to obtain Ti carbonate. Next, following the treatment of reducing and carbonizing the Ti compound, the pre-sintered body is subjected to nitriding treatment, and the Ti carbonate produced in the reduction and carbonization steps is reduced and nitrided to obtain Ti (C, N) or Ti Double carbonitride is produced.

  Next, as in Example 1, the temperature inside the heating furnace is further raised, and the pre-sintered body is heated to 1400 ° C., which is equal to or higher than the liquid phase temperature at which the binder metal constituting the binder phase melts to become a liquid phase. By holding this heated state for 120 minutes, a cemented carbide which is a sintered body in which the hard phase and the binder phase are sinter-bonded is produced.

  The cemented carbide prepared here was cooled to obtain a test piece, and the cut surface of the test piece was subjected to mirror finishing similar to that in Example 1, and the structure was observed using a scanning electron microscope. The observation results are shown in FIGS. As shown in FIGS. 3 and 4, a large number of fine particles 3 having a particle size of 50 to 300 nm are dispersed and generated in the binder phase 2 in which the WC particles 1 constituting the hard phase are bonded.

  In Example 2, the proportion of the binder phase is made larger than that of the cemented carbide of Example 1, but as in Example 1, the fine particles constituting the dispersed phase formed in the binder phase are dispersed. As shown in FIG. 4, some of the particles 3 adhere to the surface of the WC particles 1 constituting the hard phase, and form fine irregularities 4 on the surface of the WC particles 1 to suppress the grain growth of the WC particles 1. Yes.

The fine particles 3 produced in the binder phase 2 of Example 2 were analyzed by an energy dispersive X-ray analyzer, and (Ti _0.52 , W _0.48 ) (C _0.6 , N _0.4 ) Was confirmed to be a titanium-based carbonitride.

Example 3
The cemented carbide of Example 3 has a WC powder having a particle size constituting a hard phase of 6.0 μm, a Co powder having a particle size constituting a binder phase of 1.1 μm, and a Ti compound constituting a dispersed phase. It was prepared using a raw material powder mixed with TiO ₂ powder having a thickness of 1.0 μm.

Here, the raw material powder contains 10% by weight of Co powder and 2.7% by weight of TiO ₂ powder, and the balance is composed of WC powder and inevitable impurities.

  In this example, as in each of the examples described above, the raw material powder that had been pulverized and mixed was compression-molded to form a compression-molded body, and this compression-molded body was pre-sintered, and then subjected to a sintering process. Create a hard alloy.

  The cemented carbide prepared here was used as a test piece, and the cut surface of this test piece was mirror-finished in the same manner as in Examples 1 and 2, and the structure was observed using a scanning electron microscope. The observation results are shown in FIGS. As shown in FIGS. 5 and 6, a large number of fine particles 3 having a particle size of 50 to 300 nm are dispersed and generated in the binder phase 2 in which the WC particles 1 constituting the hard phase are bonded.

  Since the cemented carbide according to the third embodiment is made using WC powder having a particle size of 6.0 μm, the particle size of the WC particles 1 constituting the hard phase is the same as that of the first and second embodiments. It is larger than the hard alloy WC particles 1.

  Also in the cemented carbide according to the third embodiment, a part of the fine particles 3 constituting the dispersed phase dispersed and formed in the binder phase are formed on the surface of the WC particles 1 constituting the hard phase as shown in FIG. It adheres and forms fine irregularities 4 on the surface of the WC particles 1 to suppress the grain growth of the WC particles 1.

The fine particles 3 produced in the binder phase 2 of Example 3 were analyzed by an energy dispersive X-ray analyzer, and (Ti _0.63 , W _0.37 ) (C _0.56 , N _0.44). ) Was confirmed to be a titanium-based carbonitride.

Example 4
The cemented carbide of Example 4 has a WC powder having a particle size of 6.0 μm constituting a hard phase, a Co powder having a particle size constituting a binder phase of 1.1 μm, and a Ti compound constituting a dispersed phase. It was prepared using a raw material powder mixed with TiO ₂ powder having a thickness of 1.0 μm.

Here, the raw material powder contains 20% by weight of Co powder and 1.3% by weight of TiO ₂ powder, and the remainder is composed of WC powder and inevitable impurities.

  In the fourth embodiment, similarly to the above-described embodiments, the raw material powder that has been pulverized and mixed is compression-molded to form a compression-molded body, the compression-molded body is pre-sintered, and then subjected to a sintering process. Create cemented carbide.

  The cemented carbide prepared here was used as a test piece, and the cut surface of the test piece was subjected to mirror finishing similar to each example, and the structure was observed using a scanning electron microscope. The observation results are shown in FIGS. As shown in FIGS. 7 and 8, a large number of fine particles 3 having a particle size of 50 to 300 nm are dispersed and generated in the binder phase 2 in which the WC particles 1 constituting the hard phase are bonded.

  Since the cemented carbide according to the fourth embodiment is made using WC powder having a particle size of 6.0 μm, the particle size of the WC particles 1 constituting the hard phase is the same as that of the first and second embodiments. It is larger than the hard alloy WC particles 1.

  The cemented carbide according to Example 4 has a larger proportion of the binder phase than the cemented carbide of Example 3, but as in Example 3, the dispersed phase formed dispersed in the binder phase. As shown in FIG. 8, a part of the fine particles 3 constituting the particles adheres to the surface of the WC particles 1 constituting the hard phase, and the fine irregularities 4 are formed on the surface of the WC particles 1 to grow the particles of the WC particles 1. Is suppressed.

The fine particles 3 produced in the binder phase 2 of Example 4 were analyzed by an energy dispersive X-ray analyzer, and (Ti _0.65 , W _0.35 ) (C _0.46 , N _0.54). ) Was confirmed to be a titanium-based carbonitride.

Example 5
The cemented carbide of Example 5 uses a WC powder constituting the hard phase with a particle size of 6.0 μm, the binder phase is composed of Co, Ni, Cr ₃ C ₂ and the dispersed phase is (Ti, W ) Generated from C.

The cemented carbide according to the fifth embodiment includes a WC powder having a particle size of 6.0 μm, a Co, Ni, and Cr powder having a particle size in the range of 0.5 to 3.0 μm, and a particle size of 1.5 μm. It was prepared using raw material powder mixed with (Ti, W) C powder. Here, the raw material powder comprises 6% by weight of Co powder constituting the binder phase, 4% by weight of Ni powder, 0.7% by weight of Cr ₃ C ₂ powder, and constitutes a dispersed phase (Ti, W ) Containing 2% by weight of C powder, and the balance is composed of WC powder and inevitable impurities.

  In Example 5, the raw material powder is added with an ethanol solvent and pulverized and mixed using a ball mill in the same manner as in the above Examples. The mixed and pulverized raw material powder is taken out from the ball mill and dried. Paraffin wax is added to the pulverized and dried raw material powder in order to improve moldability in the molding process.

  The raw material powder to which the paraffin wax is added is formed into a compression-molded body having a predetermined shape using a cold isostatic pressing method. This compression-molded body is heated to about 500 ° C. in a heating furnace having a hydrogen atmosphere, and degreased. The compression molded body that has been subjected to the degreasing treatment is heated to about 900 ° C. and pre-sintered in a heating furnace in a vacuum atmosphere.

  Pre-sintering obtained by pre-sintering this compression-molded body is sintered through the following sintering process to obtain a cemented carbide as a sintered body.

  In Example 5, since (Ti, W) C powder is used as the Ti compound constituting the dispersed phase, oxidation treatment for oxidizing (Ti, W) C is performed. This oxidation treatment is performed by heat-treating the pre-sintered body to about 1000 ° C. in a heating furnace having a weak oxidation atmosphere. In this heat treatment step, oxidized (Ti, W) C is reduced and carbonized by C contained in the raw material powder to form a Ti double carbonate oxide.

Next, following the process of reducing and carbonizing the Ti compound, the pre-sintered body is nitrided. Nitriding treatment of the pre-sintered body is performed by introducing nitrogen gas into a heating furnace subjected to reduction and carbonization treatment. At this time, the nitrogen pressure in the heating furnace is about 1 kPa. Then, the pre-sintered body is heat-treated with the inside of the heating furnace being about 1000 ° C. or higher. The pre-sintered body is heated to about 1000 ° C. or higher in a nitrogen atmosphere, and the Ti double carbonate produced in the reduction and carbonization steps is reduced and nitrided to produce (Ti, W) (C, N). .

  Next, the pre-sintered body is heated to 1400 ° C., which is equal to or higher than the liquid phase temperature at which the binder metal constituting the binder phase melts to become a liquid phase. The pre-sintered body is held for 120 minutes in a state of being heated to 1400 ° C., thereby forming a cemented carbide that is a sintered body in which the hard phase and the binder phase are sinter-bonded.

  The cemented carbide prepared here was used as a test piece, and the cut surface of the test piece was subjected to mirror finishing similar to each of the above-described examples, and the structure was observed using a scanning electron microscope. The observation results are shown in FIGS. As shown in FIGS. 9 and 10, a large number of fine particles 3 having a particle diameter of 50 to 300 nm are dispersed and generated in the binder phase 2 in which the WC particles 1 constituting the hard phase are bonded.

  Since the cemented carbide according to the fifth embodiment is made using WC powder having a particle size of 6.0 μm, the WC particles 1 constituting the hard phase are the same as in the third and fourth embodiments. Compared to the WC particles 1 of the cemented carbide according to 1 and 2, it has a larger particle size.

  The cemented carbide according to the fifth embodiment uses Co, Ni, and Cr as the binder phase, but, as in the third and fourth embodiments, the fine particles constituting the dispersed phase dispersed in the binder phase are used. As shown in FIG. 10, a part of the particles 3 adheres to the surface of the WC particles 1 constituting the hard phase to form fine irregularities 4 and suppress the grain growth of the WC particles 1.

  Therefore, even if the metal constituting the binder phase is appropriately selected in consideration of the mechanical properties of the cemented carbide to be produced, the fine particles adhered to the surface of the WC particles 1 constituting the hard phase by sintering Fine irregularities 4 can be formed by the particles 3 to suppress grain growth of the WC particles.

The fine particles 3 produced in the binder phase 2 of Example 5 were analyzed by an energy dispersive X-ray analyzer, and (Ti _0.41 , W _0.59 ) (C _0.78 , N _0.22). ) Was confirmed to be a titanium-based carbonitride.

1 WC particles, 2 bonded phase, 3 fine particles, 4 fine irregularities

Claims (8)

A hard phase mainly composed of tungsten carbide (WC), a binder phase mainly composed of at least one selected from the group consisting of Co, Ni and Fe, and a particle size dispersed and generated in the binder phase is 50 to 300 nm. And a dispersed phase composed of fine particles of titanium carbonitride represented by the following general formula (1):
(Ti _1-X , W _X ) (C _1-Y , N _Y ) (1)
(In the formula, X is 0.2 to 0.6, and Y is 0.2 to 0.6.)
At least a part of the fine particles of the titanium-based carbonitride dispersed and formed in the binder phase adheres to the surface of the WC particles constituting the hard phase, and fine irregularities are formed on the surface of the WC particles. Cemented carbide characterized by that.   The part of W constituting the carbonitride is replaced with at least one selected from the group consisting of Ta, Nb, Mo, Zr, Hf, Cr, and V. Cemented carbide.   2. The binder phase is contained in a range of 5 to 30% by weight with respect to the total weight of the cemented carbide, and the dispersed phase is contained in an amount of 3 to 50% by weight based on the binder phase. Or the cemented carbide according to 2.   A cemented carbide tool, wherein the tool base is formed of the cemented carbide according to any one of claims 1 to 3. A powder composed mainly of tungsten carbide (WC) constituting the hard phase, a powder mainly composed of at least one selected from the group consisting of Co, Ni and Fe constituting the binder phase, and constituting a dispersed phase (Ti , W) C, (Ti, W) (C, N), raw material powder prepared by mixing at least one Ti compound powder selected from TiC, TiN, and Ti (C, N) Create a compression molding by compression molding
The compression molded body is heated to 600 to 900 ° C. in a heating furnace having a vacuum atmosphere or an inert atmosphere to prepare a pre-sintered body,
Next, the pre-sintered body is heated to about 1000 ° C. in a weak oxidizing atmosphere to oxidize the Ti compound mixed in the raw material powder, and the oxidized Ti compound is reduced by C contained in the raw material powder. , Carbonized to produce Ti carbonate or Ti double carbonate,
Next, the pre-sintered body is heated to about 1000 ° C. or more in a nitrogen atmosphere and subjected to nitriding treatment, and the Ti carbonate or Ti double carbonate is reduced and nitrided to obtain Ti (C, N) or Ti double coal. Produce nitride,
Next, the pre-sintered body is heated in a nitrogen atmosphere at 1350 to 1500 ° C., which is equal to or higher than the liquid phase temperature at which the metal constituting the binder phase melts and becomes a liquid phase, and is sintered for 60 to 120 minutes. As well as generating a ligation,
In the step of producing the sintered body, the WC contained in the compression-molded body is diffused into the Ti (C, N) or Ti double carbonitride so that the particle size is 50 to 300 nm. WC particles constituting the hard phase with at least a part of the fine particles of the titanium-based carbonitride being dispersedly formed in the binder phase. A method for producing a cemented carbide characterized in that fine irregularities are formed on the surface of the WC particles.
(Ti _1-X , W _X ) (C _1-Y , N _Y ) (1)
(In the formula, X is 0.2 to 0.6, and Y is 0.2 to 0.6.) When the Ti compound is TiO ₂ , the Ti compound contained in the raw material powder is immediately reduced by C contained in the raw material powder and carbonized to produce Ti carbonate. 5. A method for producing a cemented carbide according to 5.   The titanium-based carbonitride represented by the formula (1) dispersedly produced in the binder phase is obtained by nitriding the Ti carbonate or Ti double carbonate produced by reducing and carbonizing the Ti compound. 6. The method for producing a cemented carbide according to claim 5, wherein WC is produced by diffusing WC into Ti (C, N) produced by the above process.   The method for producing a cemented carbide according to claim 5, wherein the Ti compound constituting the dispersed phase is added in a range of 2 to 20% by weight in terms of TiC with respect to the binder phase.