WO2012147737A1

WO2012147737A1 - Tungsten carbide-based sinter and abrasion-resistant members using same

Info

Publication number: WO2012147737A1
Application number: PCT/JP2012/060963
Authority: WO
Inventors: 修司上野; 幸太郎古川; 賢治中原; 健司船水; 木下　聡; 真之高田; 松原　秀彰; 哲志松田; 野村　浩
Original assignee: 日本タングステン株式会社; 株式会社タンガロイ; 日本特殊合金株式会社; 一般財団法人ファインセラミックスセンター
Priority date: 2011-04-26
Filing date: 2012-04-24
Publication date: 2012-11-01
Also published as: JP2012229138A; JP5856752B2

Abstract

Provided are: a tungsten carbide-based sinter having a high grain growth inhibiting effect with respect to tungsten carbide, and having excellent chemical durability, such as corrosion resistance, in addition to mechanical strength; and abrasion-resistant members, such as heads for application tools, cutting blades, cutter blades, lens molds, and seal rings, which use the tungsten carbide-based sinter. The tungsten carbide-based sinter comprises a first phase composed primarily of tungsten carbide, and a second phase composed primarily of a carbonitride with one type or multiple types of elements selected from a group comprising Group 4 elements, Group 5 elements and Group 6 elements, wherein the volume fraction of the second phase is 0.01 percent by volume to less than 40 percent by volume, and the remainder is the first phase.

Description

Tungsten carbide-based sintered body and wear-resistant member using the same

The present invention relates to an improved tungsten carbide-based sintered body and a wear-resistant member using the same.

Carbides of elements of Group 4, Group 5 and Group 6 of the periodic table (Group IVa, Group Va and Group VIa, respectively) of the periodic table, including tungsten carbide (WC) Composite materials sintered with iron group elements such as iron (Fe), cobalt (Co), nickel (Ni) are superior in mechanical properties such as hardness, strength, and wear resistance, and are called cemented carbides. ing. Cemented carbides are used in many applications including metal cutting tools and deep drawing dies such as aluminum because of their low wear resistance at high temperatures and excellent wear resistance. .

The cemented carbide is manufactured by a powder metallurgy method in which carbide and iron group metal powders as raw materials are pulverized and mixed, and then pressed and heated to sinter. In the heating process during sintering, the iron group metal is first melted to generate a liquid phase, the flow of which causes rearrangement of the solid phase particles, and then dissolution of the solid phase particles into the liquid phase occurs. Thereafter, precipitation, growth and coalescence of solid phase particles occur in the cooling process, and a cemented carbide consisting of a columnar carbide particle phase and an iron group metal phase as a connective structure is formed.

In this case, if the growth of the carbide particles progresses too much and the particles become coarse, the mechanical properties deteriorate, so it is desirable to suppress the growth of the carbide particles and keep the particle size at about 1 μm or less. In addition, cobalt is usually used as the iron group metal forming the binder phase, but the cemented carbide using cobalt is excellent in toughness and the like, but has low hardness, the cobalt phase is easily corroded, etc. There is a problem in terms of.

In view of these problems, studies have been made on a tungsten carbide-based sintered body that has a grain growth suppressing effect and has excellent characteristics in terms of corrosion resistance and mechanical strength. For example, it is known to add vanadium carbide (VC) or chromium carbide (Cr ₃ C ₂ ) having an effect of suppressing grain growth of tungsten carbide as an additive (see, for example, Patent Document 1).
In Patent Document 2, the first phase is WC, the second phase is a double coal (nitride) containing Ti and W as main components, and the binder phase metal exists as a third phase double coal (nitride). A sintered alloy having a three-phase mixed structure is disclosed.
In Patent Document 3, Ni is 0.02 to 0.5% by weight, and one or more of carbides, nitrides, and carbonitrides of transition metals of Groups 4, 5, and 6 of the periodic table are 0.1 to 5%. 0.0% by weight, the balance being a sintered body composed of tungsten carbide and inevitable impurities, the microstructure is composed of a hard phase, a binder phase, and a reaction phase, and when the area ratio of the reaction phase is S (%), 0.1% Disclosed is a glass optical element molding die member in which P ≦ 0.1, where ≦ S ≦ 2 and the porosity is P (%).
In Patent Document 4, 1 to 15% by weight of one or more selected from iron group metals as a binder phase component, and carbides, nitrides of Group 4, 5, and 6 metals in the periodic table as solid solution phase components 1 to 20% by weight of a solid solution, carbonitride, or a solid solution thereof, and the balance is composed of a hard phase component and inevitable impurities of tungsten carbide, and the solid solution phase component is distributed substantially evenly inside the member, A cemented carbide member is disclosed in which the solid solution phase component is continuously reduced in the surface portion of the member in a region where the solid solution phase component is distributed substantially uniformly.
Patent Document 5 discloses a tungsten carbide phase, a solid solution phase composed of at least two kinds of carbides selected from the group of metals of Groups 4, 5, and 6 of the periodic table, nitrides and carbonitrides, and at least one kind of iron. And a Zr—Nb solid solution phase containing at least Zr and Nb as a solid solution phase. The average particle size d of the Zr—Nb solid solution phase with respect to the average particle size d ₁ of the tungsten carbide phase. _A cemented carbide having a ratio of ₂ (d ₂ / d ₁ ) of 0.5 to 2 is disclosed.

Japanese Patent Laid-Open No. 61-12847 JP 2002-180175 A JP 2008-0775160 A JP 2002-146466 A JP 2002-356734 A

However, the cemented carbide described in Patent Document 1 lacks chemical stability when the temperature is particularly high because the compounds of Group 4 elements, Group 5 elements, and Group 6 elements do not contain nitrogen. Has the problem.
Among the cemented carbides described in Patent Document 2, the compounds of Group 4 elements, Group 5 elements, and Group 6 elements that do not contain nitrogen (Claims 1 and 2) are the same as in Patent Document 1 above. In all cases containing nitrogen (claims 3 and after and Examples 9 to 12), the WC content is low, so the fracture toughness is as low as 74.5% or less, so the toughness of WC is sufficiently increased. Cannot be used, and its application is extremely limited.
The cemented carbide described in Patent Document 3 has a relatively large carbonitride raw material powder size of 1 to 2 μm, and therefore does not have a sufficient function of suppressing WC crystal growth, and has sufficient hardness and strength. I can't get it.
Since the composition and physical properties of the cemented carbide member described in Patent Document 4 differ depending on the location of the sintered body, the wear-resistant member that is the main object of the present invention is limited in its use, such as life Prediction is also difficult.
The cemented carbide described in Patent Document 5 does not show an example of containing nitrogen, and has the same problem as in References 1 and 2.

The present invention has been made in view of such circumstances, and has a high grain growth suppressing effect on tungsten carbide, and has a tungsten carbide-based sintered body excellent in chemical durability such as corrosion resistance in addition to mechanical strength and the same. It aims at providing wear-resistant members, such as a head part for used application tools, a cutting blade, a cutter blade, a lens type, and a seal ring.

That is, the present invention provides a tungsten carbide-based sintered body described in the following (1) to (11) and a wear-resistant member described in the following (12) and (13).
(1) A main component is a carbonitride of one or more elements selected from the group consisting of a first phase mainly composed of tungsten carbide and a group 4 element, a group 5 element, and a group 6 element. A tungsten carbide-based sintered body having a second phase, wherein the volume fraction of the second phase is 0.01 volume% or more and less than 40 volume%, and the balance is the first phase.
(2) The tungsten carbide based sintered body according to (1), wherein the volume fraction of the second phase is 0.5 volume% or more and 5 volume% or less.
(3) Of the first phase tungsten carbide, 0.01 volume% or more and less than 4 volume% of the total volume of the sintered body is an iron group element, a group 4 element, a group 5 element, and a group 6 element The tungsten carbide-based sintered body according to (1), wherein the tungsten carbide-based sintered body is substituted with a third phase mainly composed of a composite carbide and / or composite carbonitride of one or more elements selected from the group consisting of:
(4) The tungsten carbide based sintered body according to (3), wherein the third phase contains at least cobalt as an iron group element.
(5) The tungsten carbide based sintered body according to (3) or (4), wherein the volume fraction of the third phase is 0.2% by volume or less.
(6) The tungsten carbide based sintered body according to (3) or (4), wherein the volume fraction of the second phase is 4% by volume or more and 12% by volume or less.
(7) The tungsten carbide based sintered body according to any one of (3) to (6), wherein a part or all of the third phase is substituted with an iron group metal phase containing at least cobalt.
(8) The tungsten carbide based sintered body according to any one of (1) to (7), wherein the second phase contains at least molybdenum.
(9) The moles of carbon and nitrogen in the carbonitride of one or more elements selected from the group consisting of Group 4 elements, Group 5 elements and Group 6 elements that constitute the second phase 9. The tungsten carbide-based sintered body according to any one of (1) to (8), wherein a relationship of 0.2 ≦ x ≦ 0.8 is established when the ratio is x: (1-x).
(10) The tungsten carbide based sintered body according to any one of (1) to (9), wherein the crystal grains constituting the second phase have an average particle diameter of 0.03 to 1.1 μm.
(11) From the above (1), wherein at least chromium is contained in one or more elements selected from the group consisting of the Group 4 element, Group 5 element and Group 6 element in the second phase. The tungsten carbide-based sintered body according to any one of 10).
(12) A wear-resistant member using the tungsten carbide-based sintered body according to any one of (1) to (11).
(13) The wear resistant member according to (12), which is any one of a coating tool head, a cutting blade, a lens mold, a seal ring, and a cutting tool.

In the present invention, “Group 4 element” means any of titanium (Ti), zirconium (Zr), and hafnium (Hf), and “Group 5 element” means vanadium (V), niobium. One of (Nb) and tantalum (Ta) is referred to, and the “Group 6 element” refers to any of chromium (Cr), molybdenum (Mo), and tungsten (W). In the present invention, the “iron group element” refers to any of iron (Fe), cobalt (Co), and nickel (Ni).

In the tungsten carbide-based sintered body of the present invention, one or a plurality of types selected from the group consisting of Group 4 elements, Group 5 elements and Group 6 elements used for forming the second phase which is the binder phase Elemental carbonitride has a high grain growth inhibitory effect on tungsten carbide and can easily produce fine particles having a fine particle size. Therefore, the tungsten carbide-based sintered body of the present invention manufactured using such a carbonitride as a raw material has a dense structure in which grain growth of tungsten carbide is effectively suppressed and does not include coarse particles. In addition to being excellent in mechanical properties such as hardness and bending strength, it is excellent in corrosion resistance and toughness as compared with those using an iron group metal such as cobalt as a binder phase.

(A) is a SEM image (SE) of the fracture surface of the tungsten carbide-based sintered body obtained in Example 1 (addition of 2% by volume of (Ti, W) (C, N)), (B) is It is a SEM image (BSE) of the polished surface of the tungsten carbide based sintered body. (A) is an SEM image (SE) of a fracture surface of a tungsten carbide based sintered body (VC—Cr ₃ C ₂ —WC) not containing carbonitride, and (B) is the tungsten carbide based sintered body ( It is a SEM image (BSE) of the polished surface of (VC—Cr ₃ C ₂ —WC). (A) is the SEM image (SE) of the fracture surface of the tungsten carbide-based sintered body obtained in Example 2, and (B) is the SEM image (BSE) of the polished surface of the tungsten carbide-based sintered body. is there. (A) is a SEM image (SE) of the fracture surface of the tungsten carbide-based sintered body obtained in Example 3 (with vanadium carbide (1% by volume) added), and (B) is the same tungsten carbide-based sintered material. It is a SEM image (BSE) of the grinding | polishing surface of a body. (A) is the SEM image (SE) of the fracture surface of the tungsten carbide based sintered body obtained in Example 3 (added with chromium carbide (0.7% by volume) and niobium carbide (0.3% by volume)). (B) is an SEM image (BSE) of the polished surface of the tungsten carbide based sintered body. (A) is an SEM image (BSE) of the polished surface of the tungsten carbide-based sintered body obtained in Example 4 (0.5% by volume of (Ti, W) (C, N) added), (B ) Is an SEM image (BSE) of the corroded surface of the tungsten carbide based sintered body. (A) is an SEM image (BSE) of the polished surface of the tungsten carbide based sintered body obtained in Example 4 (addition of 1% by volume of (Ti, W) (C, N)), (B) It is a SEM image (BSE) of the corroded surface of the tungsten carbide based sintered body. (A) is a SEM image (BSE) of the polished surface of the tungsten carbide-based sintered body obtained in Example 4 (addition of 2% by volume of (Ti, W) (C, N)), and (B) is It is a SEM image (BSE) of the corroded surface of the tungsten carbide based sintered body. (A) is a SEM image (BSE) of the polished surface of the tungsten carbide-based sintered body obtained in Example 4 (15% by volume of (Ti, W) (C, N) added), and (B) is It is a SEM image (BSE) of the corroded surface of the tungsten carbide based sintered body. (A) is an SEM image (BSE) of the polished surface of the tungsten carbide based sintered body obtained in Example 4 (addition of 30% by volume of (Ti, W) (C, N)), (B) It is a SEM image (BSE) of the corroded surface of the tungsten carbide based sintered body. (A) is an SEM image (BSE) of the polished surface of the tungsten carbide based sintered body obtained in Example 4 (0.5% by volume of (Ti, Mo) (C, N) added), (B ) Is an SEM image (BSE) of the corroded surface of the tungsten carbide based sintered body. (A) is a SEM image (BSE) of the polished surface of the tungsten carbide based sintered body obtained in Example 4 (addition of 1% by volume of (Ti, Mo) (C, N)), (B) It is a SEM image (BSE) of the corroded surface of the tungsten carbide based sintered body. (A) is an SEM image (BSE) of the polished surface of the tungsten carbide-based sintered body obtained in Example 4 (addition of 2% by volume of (Ti, Mo) (C, N)), and (B) is It is a SEM image (BSE) of the corroded surface of the tungsten carbide based sintered body. (A) is an SEM image (BSE) of the polished surface of the tungsten carbide-based sintered body obtained in Example 4 (addition of 15% by volume of (Ti, Mo) (C, N)), (B) It is a SEM image (BSE) of the corroded surface of the tungsten carbide based sintered body. (A) is a SEM image (BSE) of the polished surface of the tungsten carbide-based sintered body obtained in Example 4 (addition of 30% by volume of (Ti, Mo) (C, N)), and (B) is It is a SEM image (BSE) of the corroded surface of the tungsten carbide based sintered body. It is a SEM image (BSE) of the polished surface of the tungsten carbide based sintered body obtained in Example 5 (Co addition amount 1 vol%, (Ti, Mo) (C, N) added 2 vol%)). It is the SEM image (BSE) of the grinding | polishing surface of the tungsten carbide base sintered compact obtained in Example 5 (Co addition amount 3.9 volume%, (Ti, Mo) (C, N) addition 2 volume%)). . (A) is the SEM image (BSE) of the polished surface of the tungsten carbide based sintered body obtained in Example 6 ((Ti, W) (C, N) added at 2% by volume), (B) is It is a SEM image (BSE) of the corroded surface of the tungsten carbide based sintered body. (A) is the SEM image (BSE) of the polished surface of the tungsten carbide-based sintered body obtained in Example 6 (5% by volume of (Ti, W) (C, N) added), (B) It is a SEM image (BSE) of the corroded surface of the tungsten carbide based sintered body. (A) is a SEM image (BSE) of the polished surface of the tungsten carbide based sintered body obtained in Example 6 (addition of 2% by volume of (Ti, Mo) (C, N)), (B) is It is a SEM image (BSE) of the corroded surface of the tungsten carbide based sintered body. (A) is an SEM image (BSE) of the polished surface of the tungsten carbide-based sintered body obtained in Example 6 (5% by volume of (Ti, Mo) (C, N) added), (B) It is a SEM image (BSE) of the corroded surface of the tungsten carbide based sintered body. (A) is an SEM image (BSE) of the polished surface of the tungsten carbide based sintered body obtained in Example 7 (addition of 2% by volume of (Ti, Mo) (C, N)), (B) It is a SEM image (BSE) of the corroded surface of the tungsten carbide based sintered body.

The tungsten carbide-based sintered body according to an embodiment of the present invention (hereinafter, may be abbreviated as “tungsten carbide-based sintered body” or “sintered body”) is mainly composed of tungsten carbide. A carbonitride of one or more elements selected from the group consisting of one phase and a group 4 element, group 5 element and group 6 element (hereinafter sometimes simply referred to as “carbonitride”) 2) having a main component as a main component. In order to exhibit the mechanical properties and heat resistance required for the sintered body, the material constituting the second phase must have high thermal conductivity while suppressing grain growth of tungsten carbide crystal grains. Required. Therefore, carbonitride that can suppress grain growth while ensuring thermal conduction was selected as a constituent material of the second phase, instead of carbide having a low grain growth suppressing effect and nitride having low thermal conductivity.
The volume fraction of the second phase is 0.01 volume% or more and less than 40 volume% of the total volume of the sintered body, and the first phase exceeds the remaining volume, that is, 60 volume% of the total volume of the sintered body. .99% by volume or less. If the volume fraction of the second phase is less than 0.01% by volume of the total volume of the sintered body, the grain growth of tungsten carbide cannot be sufficiently suppressed, and sufficient mechanical properties cannot be obtained. Further, when the volume fraction of the second phase is 40% by volume or more of the total volume of the sintered body, the toughness and strength, particularly toughness, are significantly reduced.

The volume fraction of each phase can be determined by any known method such as analysis of the in-plane distribution of each phase by image analysis of an electron microscope image, or analysis of the in-plane distribution of constituent elements using EPMA (X-ray probe microanalyzer). It can be determined using methods and apparatus. As described above, the volume fraction of the second phase is 0.01 volume% or more and less than 40 volume% of the total volume of the sintered body, and is appropriately adjusted according to the application, required mechanical characteristics, and the like. For example, in order to improve the bending strength (toughness), the volume fraction of the second phase is preferably 0.5 volume% or more and 5 volume% or less of the total volume of the sintered body.

Since the first phase and the second phase generally have different color tones, the in-plane distribution can be obtained from the electron microscope image, but the crystal particles constituting the second phase having a low volume fraction are separated from each other. Therefore, the average particle diameter can be measured by image analysis. Since the crystal particles are not necessarily spherical, for example, the area of each particle is obtained by counting the number of pixels corresponding to each particle from the binarized image, and the diameter of a circle having the same area as that particle is obtained. The particle diameter of each crystal particle is determined using a method such as setting the particle diameter of the particle. A preferable range of the average particle diameter of the crystal grains constituting the second phase is 0.03 to 1.1 μm. When the average grain size of the crystal grains constituting the second phase is within the above range, the fracture mode of the sintered body is dominated by intragranular fracture, so the fracture strength is half the grain size. Follows the inversely proportional Hall-Petch rule. Therefore, it is desirable that the average grain size of the crystal grains be as small as possible within the above range in order to obtain a tungsten carbide-based sintered body having excellent mechanical characteristics.

When the volume fraction of the second phase is high and the crystal particles constituting the first phase are present in a separated state, the grain size of the tungsten carbide crystal particles constituting the first phase is also It can be determined in the same manner as in the case of the second phase, and even when the tungsten carbide crystal particles are in contact with each other, it is possible to observe the crystal grain boundary due to the difference in crystal orientation, etc. by the corrosion treatment with alkali, etc. By doing so, the particle size of the crystal particles can be determined. The preferable particle diameter of the tungsten carbide crystal particles is 0.05 to 1 μm, and the more preferable particle diameter is 0.05 to 0.4 μm.

Note that the second phase may be composed only of the carbonitride, but may contain impurities in the raw material and inevitable impurities caused by impurities mixed in the manufacturing process. Similarly, the first phase may contain unavoidable impurities other than tungsten carbide (WC). However, since such impurities are pushed out to the grain boundary portion as the tungsten carbide crystal grains grow, the first phase is usually used. One phase consists only of substantially pure tungsten carbide.

Carbonitrides constituting the second phase are Group 4 elements, Group 5 elements and Group 6 elements, that is, titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium ( It contains one or more elements selected from the group consisting of Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo) and tungsten (W). The carbonitride preferably contains Ti as an element selected from the group consisting of Group 4 elements, Group 5 elements and Group 6 elements. Specific examples of the carbonitride constituting the second phase include (Ti, W) (C, N), (Ti, Mo) (C, N), and the like. When the molar fraction of carbon and nitrogen contained in carbonitride is x: (1-x), x is 0.2 or more and 0.8 or less, preferably 0.3 or more and 0.7 or less. It is. When x exceeds 0.8, the effect of suppressing grain growth is slightly reduced. On the other hand, if x is less than 0.2, the effect of suppressing grain growth is not significantly affected, but the thermal conductivity is remarkably lowered, so that it is not suitable for use at high temperatures, and the raw material powder is manufactured and obtained. Becomes extremely difficult.

The tungsten carbide-based sintered body is manufactured by mixing raw material powder, press-molding it into a predetermined shape, and firing it. In order to control the composition of the sintered body, it is desirable to use tungsten carbide and a desired carbonitride powder as the raw material powder, but precursors thereof may also be used. Note that tungsten carbide and carbonitride can be used as raw materials produced by any known method. The mixing ratio of tungsten carbide and carbonitride is appropriately adjusted so that the volume fraction of the first phase and the second phase in the obtained sintered body is within a desired range. The volume fraction of tungsten carbide and carbonitride powder is, for example, that the former exceeds 80% by volume of the total volume of the sintered body and 99.9% by volume or less, and the latter is 0.01% by volume of the total volume of the sintered body. More than 20% by volume.

The raw material powder can be mixed using any known method and apparatus such as a planetary ball mill. The rotation speed and mixing time of the ball mill can be appropriately adjusted so that a uniform mixture is obtained. For example, the rotational speed of the planetary ball mill is set to about 150 rpm for mixing only and about 350 rpm for grinding, and mixing is performed for about 24 to 72 hours. A solvent such as methanol may be added as a solvent during mixing.

Next, the mixed raw material powder is put into a mold or the like and pressed (for example, 100 to 300 MPa) to be pressure-molded into a predetermined shape. At that time, a binder such as paraffin may be added, for example, about 3% by weight of the raw material powder in order to enhance the binding property. Next, the raw material powder after molding is sintered to obtain a tungsten carbide-based sintered body. The sintering temperature is, for example, 1500 to 2000 ° C., depending on the type of carbonitride used as a raw material. If necessary, after degreasing and pre-sintering at a temperature of about 800 ° C., machining may be performed, and then main sintering may be performed at the above temperature. Further, after sintering, HIP (hot isostatic pressing) may be performed in an inert atmosphere such as argon or nitrogen to remove voids in the sintered structure.

In the tungsten carbide-based sintered body, among the first phase tungsten carbides, 0.01% by volume or more and less than 4% by volume of the total volume of the sintered body is an iron group element, a group 4 element, a group 5 element, and It may be substituted with a third phase mainly composed of a composite carbide and / or composite carbonitride of one or more elements selected from the group consisting of Group 6 elements. That is, in the tungsten carbide-based sintered body having the three-phase system as described above, the volume fraction of the second phase is 0.01 volume% or more and less than 40 volume% of the total volume of the sintered body. The volume fraction of the phase is 0.01 volume% or more and less than 4 volume% of the total volume of the sintered body, and the first phase exceeds the remainder, that is, 56 volume% of the total volume of the sintered body, and 99.98. % By volume or less.
If the volume fraction of the third phase is less than 0.01% by volume relative to the total volume of the sintered body, the presence of the third phase cannot be confirmed by observation, and if it exceeds 4% by volume of the total volume of the sintered body, Since the expansion coefficient becomes large, it is difficult to use for applications where the coefficient of thermal expansion is limited, such as a lens mold or a coating tool.
The third phase may contain an iron group element. In this case, it is preferable that at least cobalt is contained. Cobalt has good wettability at high temperatures with tungsten carbide, has the effect of improving the sinterability, suppressing the occurrence of unevenness in the sintered body, and improving the mechanical properties. Moreover, when only nickel or iron is added as an iron group element, it becomes difficult to control the amount of carbon. For the above reason, cobalt is preferable as the iron group element contained in the sintered body.

The tungsten carbide-based sintered body composed of the above three-phase system is the above two-phase system except that an iron group metal source (iron group metal or a salt thereof: for example, metallic cobalt or cobalt salt) is further used as a raw material. Since it can be manufactured using the same raw material and method as the tungsten carbide based sintered body made of, detailed description is omitted here.

The volume fraction of the third phase can be adjusted by appropriately changing the blending ratio of the iron group metal source used as a raw material according to the use of the sintered body and the required properties. For example, when it is necessary to ensure the bending strength of the sintered body, the preferred volume fraction of the third phase is 0.2% by volume or less of the total volume of the sintered body.

Also, the physical properties of the sintered body can be significantly changed by adjusting the volume fraction of the second phase. For example, when a sintered body is used as a material for a glass lens mold, the sintered body has a thermal expansion coefficient (preferably a desired clearance is obtained by balancing with peripheral members using a binderless cemented carbide which is currently mainstream. 4.8 to 5.3 ppm) and corrosion resistance to glass.

The iron group element including cobalt may be present in the form of substituting part or all of the third phase as a metal phase, but complex carbides with groups 4, 5, and 6 in the third phase (for example, W ₃ Co ₃ C), composite nitride, or composite carbonitride.

Further, a carbide of one or more elements selected from the group consisting of Group 4, Group 5 and Group 6 elements may be added as a raw material. In this case, the carbide is included as a component of the third phase. However, the carbide may be present in a form in which the carbide is dispersed in the second phase.

For the tungsten carbide-based sintered body composed of a three-phase system, as in the case of the two-phase system, an analysis of the in-plane distribution of each phase by image analysis of an electron microscope image and an EPMA (X-ray probe microanalyzer) were used. The volume fraction of each phase can be obtained from analysis of in-plane distribution of constituent elements.

The mechanical properties of the tungsten carbide-based sintered body obtained as described above can be measured according to a conventional method. Specific examples of the mechanical properties include normal temperature or high temperature hardness (Rockwell hardness and Vickers hardness), fracture toughness (K1c), bending strength (bending strength), volumetric thermal expansion coefficient, and the like.

The tungsten carbide-based sintered body according to one embodiment of the present invention can be suitably used for wear-resistant members such as a coating tool head, a cutting blade, a cutter blade, a lens mold, and a seal ring.

Next, examples carried out for confirming the effects of the present invention will be described.
Example 1: Production of tungsten carbide based sintered body (1)
Put tungsten carbide and (Ti, W) (C, N) powder (see Table 1 for carbon nitride addition amount (volume%)) into a ball mill (ball material is low cobalt cemented carbide) and add methanol. And pulverized and mixed for 96 hours. After evaporating methanol, hot pressing was performed in an Ar atmosphere at a pressure of 25 to 30 MPa and 1700 to 1900 ° C., and then HIP treatment was performed in an Ar atmosphere at 1700 ° C. and 180 MPa. In order to selectively increase the nitrogen mole fraction of carbonitride, the atmosphere during HIP treatment may be a mixed atmosphere of Ar and N ₂ .

Rockwell hardness (HRA) and Vickers hardness (Hv), fracture toughness (plane strain fracture toughness: K1c) and bending strength (TRS) at room temperature of the obtained tungsten carbide-based sintered body were JIS, respectively. It was measured according to Z 2245, JIS Z 2244, JIS G 0202, and JIS Z 2203.

Table 1 shows the relationship between the amount of (Ti, W) (C, N) added (volume% with respect to the total volume of the sintered body: the same applies hereinafter) and the mechanical properties of the sintered body. In addition, an SEM image (SE) of a fracture surface of a tungsten carbide-based sintered body obtained from a raw material added with 2.0% by volume of (Ti, W) (C, N) and an SEM image (BSE) of a polished surface, They are shown in FIGS. 1 (A) and (B), respectively.
The “TC amount” represents the total carbon amount, and the relative density is a relative value when the theoretical density on the powder composition of (Ti, W) (C, N) is 100% (the same applies hereinafter).

It can be seen that in all cases, the obtained tungsten carbide based sintered body has high hardness, fracture toughness and bending strength. It can also be seen that the bending strength reaches the peak value when the amount of carbonitride added is 1.0 to 5.0% by volume.

In FIGS. 1A and 1B, the presence of a plurality of phases having different colors is shown, but the black portion is a carbonitride phase (second phase), and the dark ash and light ash portions are It is a tungsten carbide (WC) phase (first phase).
For comparison, FIGS. 2A and 2B show an SEM image (SE) of a fracture surface of a tungsten carbide-based sintered body (VC—Cr ₃ C ₂ —WC) containing no carbonitride and a polished surface. Although SEM images (BSE) are shown, the grain growth of tungsten carbide is suppressed by the addition of (Ti, W) (C, N) by comparing these with FIGS. 1 (A) and (B). It was strongly suggested that it contributed to the improvement of physical characteristics.
Further, when the average particle size of the second phase was measured, it was found to be a minimum of 0.03 μm to a maximum of 0.4 μm.

Example 2: Production of a tungsten carbide-based sintered body (2)
A sintered body was produced under the same conditions as in Example 1 except that (Ti, Mo) (C, N) was used as the metal carbonitride. Table 2 shows the relationship between the amount of carbonitride added (volume%) and the mechanical properties of the obtained sintered body. Further, the SEM image (SE) of the fracture surface and the SEM image (BSE) of the polished surface of the tungsten carbide-based sintered body obtained from the raw material added with 15% by volume of (Ti, Mo) (C, N), respectively, It shows to FIG. 3 (A) and (B).

As in Example 1, in all cases, the obtained tungsten carbide-based sintered body is found to have high hardness, fracture toughness, and bending strength. In FIGS. 5 and 6, the existence of three phases having different color tones is clearly shown. From the measurement results of the in-plane distribution of each element using EPMA, dark gray to black portions are (Ti, Mo). (C, N) as the main component (second phase) (particularly, the portion rich in Ti and N is black), and the light gray portion is the phase (first phase) mainly containing tungsten carbide. 1 phase).
From the comparison between FIGS. 3 (A) and 3 (B) and FIGS. 2 (A) and 2 (B), the grain growth of tungsten carbide is also suppressed by the addition of (Ti, Mo) (C, N). Was strongly suggested. In particular, the range in which the physical properties are excellent is a range in which the amount of carbonitride added is 0.5 to 5.0% by volume. As a composite carbonitride, it can be seen that (Ti, Mo) (C, N) has a higher grain growth inhibiting effect than (Ti, W) (C, N), and the effect is remarkable even in a small amount. .

Example 3: Production of tungsten carbide based sintered body (3)
The same conditions as in Example 1 except that (Ti, W) (C, N) (2% by volume) was used as the metal carbonitride, and metal carbide (see Table 3 for types and addition amounts) was added as necessary. A sintered body was produced below. Table 3 shows the relationship between the metal carbide and its addition amount (% by volume) and the mechanical properties of the sintered body. 4A and 4B show the SEM image (SE) of the fracture surface and the SEM image (BSE) of the polished surface of the tungsten carbide-based sintered body obtained from the raw material to which vanadium carbide (1% by volume) is added. In addition, an SEM image (SE) of a fracture surface of a tungsten carbide-based sintered body obtained from a raw material added with chromium carbide (0.7% by volume) and niobium carbide (0.3% by volume) and an SEM image of a polished surface ( BSE) is shown in FIGS. 5 (A) and 5 (B).

As in Examples 1 and 2, in all cases, the obtained tungsten carbide-based sintered body is found to have high hardness, fracture toughness and bending strength. 4 (A) and 4 (B) and FIG. 5 (A), it can be seen that these sintered bodies are also composed of two phases having different colors. In FIG. 5B, a dark black structure is observed in a region corresponding to the second phase containing carbonitride as a main component, but the distribution of tungsten and carbon is relatively small from the results of EPMA measurement. Is considered part. By adding vanadium carbide (VC), which is usually added as a grain growth inhibitor together with carbonitride, the grain growth inhibiting effect becomes more remarkable. Even when chromium carbide (Cr ₃ C ₂ ) that maintains high temperature characteristics (especially oxidation resistance) is added, the high temperature characteristics can be improved while maintaining other characteristics.

Example 4: Production of tungsten carbide based sintered body (4)
Tungsten carbide and (Ti, W) (C, N) or (Ti, Mo) (C, N) powder (see Tables 4 and 5 for carbon nitride addition amount (volume%)) ball ball (ball material) Was added to low-cobalt cemented carbide), methanol was added, and pulverized and mixed for 96 hours. After evaporation of methanol, about 3% of paraffin was added, pressed at a pressure of 100 MPa, presintered and degreased at 700 to 800 ° C. under normal pressure, and then main sintered at 1900 to 2100 ° C. . Tables 4 and 5 show the relationship between the amount of carbonitride added (% by volume) and the mechanical properties of the obtained sintered body. Further, carbonization obtained from a raw material to which (Ti, W) (C, N) is added in an amount of 0.5% by volume, 1% by volume, 2% by volume, 15% by volume, and 30% by volume of the total volume of the sintered body. The polished SEM image (BSE) and the corroded SEM image (BSE) of the tungsten-based sintered body are respectively shown in FIGS. 6 (A) and (B), FIGS. 7 (A) and (B), and FIG. 8 ( A) and (B), FIGS. 9A and 9B, and FIGS. 10A and 10B, (Ti, Mo) (C, N) is added to 0.5% of the total volume of the sintered body. SEM image (BSE) of polished surface and SEM image (BSE) of corroded surface of tungsten carbide based sintered body obtained from raw materials added by volume%, 1 volume%, 2 volume%, 15% volume%, and 30 volume% 11 (A) and (B), FIG. 12 (A) and (B), FIG. 13 (A) and (B), respectively. FIG 14 (A) and (B), and shown in FIG. 15 (A) and (B).

Except for the case where the addition amount of (Ti, W) (C, N) shown in FIGS. 6 (A) and 6 (B) is 0.5% by volume, the obtained sintered body has grain growth of tungsten carbide crystal grains. Is suppressed, and it can be seen that it has sufficiently high Rockwell hardness and Vickers hardness.
Further, as a result of elemental mapping, it was found that Co mixed at the stage of mixing does not exist alone but exists as carbonitride containing W. The amount was 0.10% by volume of the whole.

Example 5: Production of tungsten carbide based sintered body (5)
Tungsten carbide, (Ti, Mo) (C, N) and cobalt (Co) powder (see Table 6 for carbonitride addition (volume%) and cobalt addition (wt%) see Table 6) The material was put in a low cobalt cemented carbide), methanol was added, and pulverized and mixed for 96 hours. After evaporating methanol, about 2.2% of paraffin was added, hot pressing was performed at 1530 ° C. in an Ar atmosphere, and then HIP treatment was performed at 1340 ° C., 40 MPa, Ar atmosphere. Table 6 shows the relationship between the amount of carbonitride added (volume%) and the mechanical properties of the obtained sintered body. Also, tungsten carbide-based firing obtained from a raw material obtained by adding (Ti, Mo) (C, N) to 2% of the total volume of the sintered body and Co to 1% by volume and 3.9% by volume of the total volume of the sintered body. The SEM image (BSE) of the polished surface and the SEM image (BSE) of the corroded surface are shown in FIGS. 16 and 17, respectively.

In addition to the first phase composed of tungsten carbide and the second phase mainly composed of carbonitride, the presence of a third phase having a high cobalt concentration was confirmed. It is not clear whether cobalt is present in the third phase as a metal or as a carbonitride.

Example 6: Production of a tungsten carbide based sintered body (6)
Except for using (Ti, W) (C, N) or (Ti, Mo) (C, N) nanopowder as carbonitride (see Table 7 for carbonitride types and addition amount (volume%)). A sintered body was produced under the same conditions as in Example 1 or 2. Table 7 shows the relationship between the type and addition amount (% by volume) of carbonitride and the mechanical properties of the obtained sintered body. Further, an SEM image of a polished surface of a tungsten carbide-based sintered body obtained from a raw material to which (Ti, W) (C, N) is added at 2.0 volume% and 5.0 volume% of the total volume of the sintered body ( BSE) and SEM images (BSE) of the corroded surface are shown in FIGS. 18A and 18B, and FIGS. 19A and 19B, respectively. (Ti, Mo) (C, N) are sintered. The SEM image (BSE) of the polished surface and the SEM image (BSE) of the corroded surface of the tungsten carbide-based sintered body obtained from the raw material added with 2% by volume and 5% by volume of the total body volume are shown in FIG. ) And (B), and FIGS. 21 (A) and (B).

Example 7: Production of a tungsten carbide based sintered body (7)
Sintered under the same conditions as in Example 4 except that (Ti, Mo) (C, N) nanopowder (2.0% by volume of the total volume of the sintered body: see Table 7) was used as the carbonitride. The body was manufactured. The mechanical properties of the obtained sintered body were as shown in Table 8. Further, an SEM image (BSE) of the polished surface and a SEM image (BSE) of the corroded surface of the tungsten carbide based sintered body are shown in FIGS. 22 (A) and 22 (B), respectively.

Example 8: Use of tungsten carbide-based sintered body for coating tool head portion WC-2 volume% (Ti _0.3 W _0.7 ) (C _0.2 N _0.8 ) -0.2 volume% Co within the scope of the present invention For coating tools used for coating a film-like member, coating a panel-like member, especially a step of applying a coating solution such as a color resist on the surface of a glass substrate when manufacturing a liquid crystal display panel It is the Example used for the front-end | tip member (head part).
Comparative samples outside the scope of the present invention are used as comparative samples 1 to 3, and the coating tool tip member is fixed to a stainless steel member (coating tool body) with a bolt and is precisely ground to obtain the coating tool of the present invention. be able to. The color resist was apply | coated to the glass substrate surface when manufacturing the liquid crystal display panel of a magnitude | size of 3.2 m x 2.4 m with the obtained application tool.
As a comparative sample,
Comparative sample 1 WC-8 vol% Co
Comparative sample 2 WC-6 vol% TiC
Comparative Sample 3 WC-6% by volume TiN-2% by volume Co
Was used as a tip member for a coating tool.
When the film thickness was measured after coating and drying using this example, it was constant, and the variation was 30% or more small for any of the comparative samples, and a very good coating film could be formed. In the film, no streak or unevenness due to coating was observed. In addition, the same coating was performed with fatty acid, rust preventive agent, metal-containing coating agent, magnetic powder coating agent, ceramic powder coating agent, etc., but the film thickness was uniform for all the comparative samples, There were no streaks or irregularities. Furthermore, for any of these applications, surface roughness, chipping, wear, corrosion, etc. do not occur with respect to 1000 hours of accelerated durability use, and performance degradation over time is small for any of the comparative samples. became.

Example 9: Use of a tungsten carbide-based sintered body for a cutting blade Sintering of WC-2 volume% (Ti _0.3 W _0.7 ) (C _0.8 N _0.2 ) -0.5 volume% Co within the scope of the present invention It is the Example which used the body for the cutting blade of a sheet-like member.
Comparative samples outside the scope of the present invention were used as comparative samples 1 to 3, and 500 sheets of copy paper (PPC paper) were stacked, and a continuous cutting test was performed in a state where the blade edge had moisture. The edge angle was 30 degrees.
As a comparative sample,
Comparative sample 1 WC-8 vol% Co
Comparative sample 2 WC-6 vol% TiC
Comparative Sample 3 WC-6% by volume TiN-2% by volume Co
Was used as a cutting blade material.
When the blade edge wear width was measured after cutting 1000 times, the comparative sample was 80 to 300 μm, whereas the example was 40 μm or less, and the amount of corrosion wear generated on the blade edge was clearly reduced. .

Example 10: Use of tungsten carbide based sintered body for lens mold WC-2 volume% (Ti _0.8 W _0.2 ) (C _0.6 N _0.4 ) -0.7 volume% Cr ₃ C ₂ within the scope of the present invention This is an example in which a sintered body of WC-2.7% by volume (Ti, W, Cr, Nb) (CN) using -0.3% by volume NbC as an input material is used for the lens mold.
As an evaluation of oxidation resistance, heat treatment was performed under the conditions of air atmosphere, 800 ° C., and 1 hour, using the alloy of the present invention as Sample 1 and out-of-range comparative samples as Comparative Samples 1, 2, and 3.
As a comparative sample,
Comparative Sample 1 WC-9 volume% TiC-2 volume% TaC-0.5 volume% VC-0.5 volume% Cr ₃ C ₂
Comparative Sample 2 WC-2 vol% Co-5 vol% TiC
Comparative sample 3 WC-11 vol% Co
Was used as a lens mold material.
After the heat treatment, the weight increase per unit area of the sample (oxidation increase g / m ² ) was measured. As a result, Comparative Sample 1 was 160 g / m ² , 1 was 180 g / m ² , and 3 was an oxidation increase of 200 g / m ^2. Compared to that, the example was 24 g / m ² and had very high oxidation resistance.

Example 11: Use of a tungsten carbide-based sintered body for a wear-resistant plate a) WC-2 vol% (Ti _0.8 Mo _0.2 ) (C _0.6 N _0.4 ) (Example 1) and b) within the scope of the present invention Each sintering of WC-2 volume% (Ti _0.8 W _0.2 ) (C _0.6 N _0.4 ) (Example 2), c) WC-35 volume% (Nb _0.4 Ta _0.2 Mo _0.2 Zr _0.2 ) (C _0.6 N _0.4 ) It is the Example which used the body for the abrasion-resistant board of pulverizer parts.
For the evaluation of wear resistance, the alloy of the present invention and comparative samples outside the range were used as comparative samples 1, 2, and 3, and blasting was performed under the following conditions.
Wear resistance test conditions Equipment: Blasting equipment Blasting time: 30 seconds Particles: SiC
Distance from nozzle to sample: 118mm
Blast irradiation area: 20 x 20 mm
As a comparative sample,
Comparative Sample 1 WC-9 volume% TiC-2 volume% TaC-0.5 volume% VC-0.5 volume% Cr ₃ C ₂
Comparative Sample 2 WC-2 vol% Co-5 vol% TiC
Comparative sample 3 WC-11 vol% Co
Was used as a crusher part material.
When the surface roughness Ra of the sample was measured after the blast treatment, the sintered body of the example was compared with the comparative sample 1 where Ra = 185 nm, 2 was Ra = 320 nm, and 3 was Ra = 500 nm. Both a), b) and c) used above had Ra = 10 nm and had very high wear resistance.

Example 12: Use of tungsten carbide based sintered body for mechanical seal ring WC-2 volume% (W _0.5 Cr _0.3 V _0.2 ) (C _0.5 N _0.5 ) -3.95 volume% within the scope of the present invention. This is an example in which a sintered body of W ₃ Co ₃ (CN) is used for a mechanical seal ring.
As a sliding test, as a mechanical seal ring for a seawater pump, An unbalanced structure with V> 1 was used, and the material was used for the seal ring on the fixed side. The floating side facing this was made of silicon carbide.
Under this condition, it was incorporated into the shaft as a pump mechanical seal, and seawater was pumped up. The surface pressure of the mechanical seal was 0.12 MPa, the sliding speed was 5 m / sec, and it was performed under the conditions of fresh water and seawater.
The alloy of the present invention was tested for 2000 hours using Sample 1 as a comparative sample and Comparative Samples 1 and 2 as out-of-range comparative samples.
As a comparative sample, comparative sample 1 WC-4 vol% Co
Comparative sample 2 WC-6 vol% TiC
Comparative Sample 3 WC-6% by volume TiN-2% by volume Co
Was used as a mechanical seal ring material.
When the difference in level between the corroded part and the non-corroded part was measured after use, compared with the comparative sample having a level difference of 4 to 18 μm, the wear level in the example was clearly smaller than 1 μm. In the test, it appeared more noticeably at 2 μm with respect to 20 to 81 μm.

Example 13: Use of tungsten carbide based sintered body for cutting tool WC-2 volume% (Ti _0.3 W _0.7 ) (C _0.5 N _0.5 ) -0.1 volume% Co and Ni within the scope of the present invention When the sintered body composed of a composite carbonitride of W and W is used as an insert for cutting edge-replaceable cutting tools with the present invention sample 1 as a comparative sample 1, 2 and 3 as comparative samples outside the range, Evaluation was performed under the following test conditions.
Work material: Iron-based sintered metal Tool shape: DCMW11T308
Cutting speed: 150 m / min Cutting depth: 0.15 mm
Feed amount: 0.1mm / rev
Tool life criterion: flank wear amount of 0.03 mm or more A comparative sample outside the scope of the present invention was produced in the same manner as Sample 1 of the present invention.
As a comparative sample,
Comparative sample 1 WC-8 vol% Co
Comparative sample 2 WC-6 vol% TiC
Comparative Sample 3 WC-6% by volume TiN-2% by volume Co
Were used as inserts for cutting edge exchangeable cutting tools.
When the iron-based sintered metal was cut using the above sample, the time until the flank wear amount of the comparative sample became 0.3 mm or more was 5 to 10 minutes, whereas the sample of the present invention was The time until the flank wear amount of No. 1 became 0.3 mm or more was 15 minutes or more, and the inventive sample 1 was clearly superior in wear resistance than the comparative sample.

Claims

A first phase mainly composed of tungsten carbide;
Having a second phase mainly composed of a carbonitride of one or more elements selected from the group consisting of Group 4 elements, Group 5 elements and Group 6 elements;
The tungsten carbide-based sintered body, wherein the volume fraction of the second phase is 0.01 volume% or more and less than 40 volume%, and the balance is the first phase.
2. The tungsten carbide based sintered body according to claim 1, wherein the volume fraction of the second phase is 0.5 volume% or more and 5 volume% or less.
Of the first-phase tungsten carbide, 0.01 vol% or more and less than 4 vol% of the total volume of the sintered body is composed of an iron group element, a group 4 element, a group 5 element, and a group 6 element 2. The tungsten carbide-based sintered body according to claim 1, wherein the tungsten carbide-based sintered body is substituted with a third phase mainly composed of a composite carbide and / or composite carbonitride of one or more elements selected from the above. .
The tungsten carbide-based sintered body according to claim 3, wherein the third phase contains at least cobalt as an iron group element.
The tungsten carbide-based sintered body according to claim 3 or 4, wherein the volume fraction of the third phase is 0.2% by volume or less.
The tungsten carbide-based sintered body according to claim 3 or 4, wherein the volume fraction of the second phase is 4% by volume or more and 12% by volume or less.
The tungsten carbide-based sintered body according to any one of claims 3 to 6, wherein a part or all of the third phase is substituted with an iron group metal phase containing at least cobalt.
The tungsten carbide-based sintered body according to any one of claims 1 to 7, wherein the second phase contains at least molybdenum.
The molar ratio of carbon and nitrogen in the carbonitride of one or more elements selected from the group consisting of the Group 4 element, Group 5 element and Group 6 element, constituting the second phase, 9. The tungsten carbide-based sintered body according to claim 1, wherein a relationship of 0.2 ≦ x ≦ 0.8 holds when x: (1−x).
The tungsten carbide-based sintered body according to any one of claims 1 to 9, wherein an average particle diameter of crystal grains constituting the second phase is 0.03 to 1.1 µm.
The at least one element selected from the group consisting of the Group 4 element, Group 5 element and Group 6 element in the second phase contains at least chromium. 11. The tungsten carbide based sintered body according to any one of 10 above.
A wear-resistant member using the tungsten carbide-based sintered body according to any one of claims 1 to 11.
The wear-resistant member according to claim 12, wherein the wear-resistant member is any one of a coating tool head, a cutting blade, a lens mold, a seal ring, and a cutting tool.