WO2005087418A1

WO2005087418A1 - Sintered tool and method for production thereof

Info

Publication number: WO2005087418A1
Application number: PCT/JP2005/004351
Authority: WO
Inventors: Masahiro Iwasaki; Hidefumi Yanagita; Masaaki Ikebe
Original assignee: Sanalloy Industry Co., Ltd.
Priority date: 2004-03-12
Filing date: 2005-03-11
Publication date: 2005-09-22
Also published as: JP4726781B2; JPWO2005087418A1

Abstract

A sintered tool, which has a surface layer portion containing boron B and/or silicon Si in an amount in a range of 0.010 to 2.0 wt %, wherein said surface layer portion contains hard particles such as WC in a content higher than that in the inner portion; and a method for producing the sintered tool which comprises compressing a mixed powder of the above hard particles and a binder metal such as Co to form a green compact having a desired shape, sintering the green compact, coating the surface of the resultant sintered compact with a boron and/or silicon applying agent, and subjecting the coated sintered compact to a heat treatment in vacuum wherein the coated compact is heated and kept within a temperature range which is lower than the solid phase temperature of the sintered compact and in which range a melt containing boron and/or silicon is formed in the sintered compact. In the above-mentioned heat treatment, boron and/or silicon in the boron and/or silicon coating layer is diffused into the surface layer portion, and a melt containing boron and/or silicon in the surface layer portion is diffused and moved into the inner portion, to thereby achieve the distribution density of hard particles in the surface layer portion of the sintered compact which is higher than that in the inner portion. The above sintered tool, wherein the above hard particles are bound via the above binder metal, exhibits the combination of an enhanced surface hardness and excellent toughness, which is achieved by the hardening without the growth of the hard particles.

Description

Specification

Sintering tool and its manufacturing method

Technical field

The present invention relates to a sintered tool in which hard particles such as tungsten carbide WC and titanium carbide TiC are bonded via an iron-based binder metal such as cobalt nickel, and a method for producing the same.

Background art

[0002] A sintered tool generally uses an iron group metal (for example, nickel Ni or cobalt Co) as a binder, and forms hard particles, for example, carbide (for example, tungsten carbide WC, titanium carbide TiC), nitride, Alternatively, it is a tool using a sintered body composed of fine carbonitride particles dispersed.Since the sintered body is excellent in hardness, heat resistance, and impact resistance, cutting tools ゃ plastic working tools, Widely used for rock drill bits for civil mines.

[0003] A sintered tool is a two-phase sintered body composed of a relatively soft and stable heat-resistant binder metal phase and high hardness and fine hard particles. When the binder metal is reduced by increasing the content of particles, the sintered body has a higher surface hardness but lower toughness.On the other hand, when the content of hard particles is reduced and the content of the binder metal is increased, On the other hand, the sintered body has a high toughness but a relatively low surface hardness and a low wear resistance. Further, as the particle size of the hard particles of the sintered body decreases, the surface hardness increases, but the toughness decreases. Due to such properties of the sintered body, the sintered body or cermet is generally used by appropriately adjusting the composition of the binder metal and the hard particles and the particle size distribution of the hard particles according to the intended use. I have.

[0004] Also, a sintered body that is excellent in both hardness and toughness is required, and techniques related to this are also known. Patent Document 1 discloses that a compact compacted from a carbide and a binder metal is heated and heated in a gas carburizing atmosphere, the surface is carburized, and the carburized material is heated in a vacuum and sintered. In this technique, a hard layer is formed on the surface, and the inner portion is made of a cermet with high toughness and a significantly hardened surface layer. Patent Document 1: Japanese Patent Publication No. 59-17176

Disclosure of the invention

Problems to be solved by the invention

[0006] However, the sintering method involving carburization described above is not suitable because the hardened layer is small when the hard alloy is used by grinding because the hardened layer depth is small. Was. In particular

On the other hand, in Ni-based or Co-based sintered tools, there is a restriction such as softening and softening, because graphite tools are used for carburizing.

[0007] Therefore, a first object of the present invention is to provide a sintered body having high surface hardness and excellent toughness obtained by hardening the particles of high melting point compound particles without growing the particles based on the hard sintered body. They want to provide tools.

[0008] A second object of the present invention is to provide a method for producing a sintered tool having surface hardness and toughness by hardening the surface of a sintered body. An object of the present invention is to provide a manufacturing method including a surface hardening treatment with a small dimensional change in the manufacturing process.

Means for solving the problem

[0009] The sintered tool of the present invention comprises hard particles and an iron-based binder metal, and has a surface layer containing boron B and / or silicon silicon in a weight range of 0.010 to 2.0%. Therefore, boride and / or silicate of the binder metal is distributed, and the surface layer is made to have a high hardness as a higher distribution density of hard particles than the inner part, and the other inner part is made of a nodder metal. This ensures high toughness, which results in a sintered tool with excellent surface hardness and internal toughness.

The invention's effect

[0010] In the sintered tool of the present invention, a sintered body composed of hard particles and a binder metal is formed in a desired shape, a boron and / or silicon coating layer is formed on the surface of the sintered body, and heat treatment is performed in a vacuum. Is performed to form a low-melting eutectic melt containing boron and / or silicon on the surface layer, so that the heat treatment process diffuses and moves the eutectic melt from the surface layer toward the inside. The surface layer reduces the content of binder metal and increases the distribution density of hard particles. is there. Due to this, the boron and / or silicon forms a boride and / or silicide phase (which may be a boriding compound) formed by the reaction with the iron group metal, and the hard particles have a high density distribution. The large surface layer can be formed into a thick layer, and a tool that combines the hardening of the surface layer and the high toughness of the internal part is formed.

[0011] In the manufacturing method of the present invention, a predetermined coating layer is formed on the surface of a sintered body having a desired shape which has been sintered and densified in advance, and heat treatment is performed. Therefore, unlike the conventional liquid-phase sintering, the amount of deformation during heat treatment is small, because heating and holding are performed at a temperature below the melting point (below the eutectic point) where no melt is generated. In the surface layer portion, precipitation of the enamel and / or silicate phase and a high distribution density of the hard particles are caused, whereby a surface layer portion having high hardness can be formed.

Hereinafter, the present invention will be described in detail based on specific examples.

Brief Description of Drawings

FIG. 1 shows a method for manufacturing a sintered tool according to an embodiment of the present invention, in which fine hard particles (particle diameter: 1 to 2 m) are immersed in a 9% BC coating solution for coating. Cross section of sintered body after heat treatment

Four

In the metal micrograph of the weave, (A) shows the inner part and (B) shows the surface part, respectively.

[FIG. 2] By a method for manufacturing a sintered tool according to an example of the present invention, coarse hard particles (particle diameter: 3 to 6 m) were immersed in a 9% coating solution of BC, coated and heat-treated. Cross section metal set of sintered body

Four

FIG. 3 is a view showing a change in hardness in a surface force depth direction of a sintered body manufactured by a manufacturing method according to Example 1 of the present invention.

FIG. 4 is a view similar to FIG. 3 according to another embodiment 2.

FIG. 5 is a view similar to FIG. 3, according to yet another embodiment 3.

FIG. 6 is a schematic view of a CVD apparatus for forming a coating layer.

FIG. 7 is a diagram showing a change in hardness in a surface force depth direction of a sintered body manufactured by a manufacturing method according to Example 4 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION [0013] In the present invention, the sintered tool has a force integrally formed from an inner part and a surface layer formed by heat treatment so as to surround the inner part. Basically, the inner part is formed of hard particles and hard particles. It contains the binder metal that binds these particles, and the surface layer necessarily contains hard particles and boron B and / or silicon silicon. The surface layer portion may contain a binder metal but has a lower content than the internal portion, or preferably does not substantially contain it, in order to increase the surface hardness.

[0014] The hard particles in the sintered tool include carbides, nitrides, or carbonitrides. In particular, as carbides, WC, TiC, TaC, NbC, VC, CrC, and nitrides such as TiN, TaN, NbN,

twenty three

VN, CrN, ZrN force At least one kind or two or more kinds are used.

2

[0015] The other binder metal is at least one selected from iron group metals, that is, Fe, Ni, and Co. From the viewpoints of corrosion resistance, heat resistance, and acid resistance, Ni or Co can be preferably used. Ni and Co form a solid solution of B in the surface layer and, in the presence of WC, form their hard borides, NiWB and CoWB, and contribute to surface hardening. In the case of silicon silicon, Ni and Co form a solid solution of Si in the surface layer and form the hard silicide NiWSi, CoWSi in the presence of WC to form a surface.

4 4

Contributes to hardening.

[0016] The inner part is a sintered body composed of hard particles, a binder metal, and a sintered body. The content ratio of the binder metal to the hard particles is in the range of 5:95 to 40:60. is there. If the content ratio of the hard particles is lower than 5:95, the binder metal is too small to form a sintered body. If the content ratio is greater than 40:60, the sintered body with less hard metal cannot be sufficiently hardened

[0017] The content ratio of the binder metal to the hard particles is preferably in the range of 5:95 to 30:70. The ratio of this content is selected depending on the application of the sintering tool. However, in general, in an application requiring toughness, particularly impact resistance, together with the surface hardness, the above-described mixing amount range is used. Among them, the hard particles are reduced and the content ratio of the binder metal is increased. On the other hand, for applications requiring particularly high surface hardness and abrasion resistance, the content ratio of the hard particles should be increased within the above range.

On the other hand, the surface layer portion of the sintered tool is formed by diffusing boron B and / or silicon Si during the heat treatment of the sintered body having the above-described composition as described later. And And / or silicon-containing layers are utilized.

[0019] In the present invention, the surface layer contains boron B or silicon Si alone or in a total weight range of 0.010 to 2.0%. Also, the distribution density of hard particles is increased. In particular, the content of boron or silicon in the surface layer is preferably in the range of 0.050 to 1.0%. When both boron and silicon are contained, the total amount is preferably in the above range.

[0020] Noinder metal is reduced from the inner part. Reduce the content of boron B or silicon Si to 0.

The content of 010-2.00% is to secure the hardness of the surface layer. If the content of boron or silicon is less than 0.010%, the diffusion movement of the binder metal from the surface layer to the inside during the diffusion heat treatment. On the other hand, if it exceeds 2.00%, the surface layer cannot follow the volume change accompanying the internal diffusion of the binder metal phase, and surface cracks are likely to occur during the diffusion heat treatment. In particular, by setting the boron or silicon content to 0.050-1.0%, the diffusion of the binder metal from the surface layer to the inside can be increased, and the surface crack can be effectively prevented. effective. As a result, the surface layer portion has a relatively low binder metal content and a high hard particle content as compared with the internal portion. This makes it possible to reduce the average spacing between adjacent hard particles, which is also, by volume, the distribution density of the hard particles being higher than that of the inner part, and Due to the particles, the surface hardness is higher than the inner part.

[0021] The distribution density of the hard particles is highest near the surface in the surface layer portion, is reduced in the depth direction of the surface layer portion, and approaches the distribution of the internal portion. With such a gradient distribution of hard particles, the content of the solder metal is made lower in the surface layer than in the inner part, and the hardness distribution also decreases from near the surface to the inner part. And incline.

[0022] The content of the binder metal element is preferably an average value within a surface force depth of 0.5 mm of the surface layer portion, and is preferably 2% or less by weight. In this way, the surface layer of the tool of the present invention is substantially composed of the hard particle phase and the boride and Z or silicate phases, and is hardened by the aggregation of the hard particles and boron and Z or the silicon compound. High surface hardness can be obtained on the tool surface.

In the sintered tool of the present invention, the average particle size of the hard particles in the sintered tool is preferably , 0.2-15 / zm. The finer the hard particles, the greater the hardness, but if it is less than 0.1, the amount of change in the bound carbon and nitrogen of the hard particle phase increases, and the stability in terms of surface hardness can be maintained. Disappears. On the other hand, if it exceeds 15 m, it is better to avoid it because the wear resistance decreases. Although the particle size of the surface layer portion and the internal portion varies depending on the application of the tool and the shape, in particular, the average particle size in the range of 0.5-10 / zm is more preferably used.

[0024] The particle size distribution of the hard particles is substantially the same between the surface layer portion and the internal portion of the sintered tool of the present invention without any particular difference. In the surface layer, as described above, the binder metal content is reduced, and the structure of the surface layer is such that fine hard particles are densely distributed, and the surface layer is closer to each other than the inner part. The average spacing between adjacent hard particles can be reduced. Such surface layer microstructure force and the hardness of the surface layer composed of hard particles including borides are increased, the friction coefficient is reduced, and the wear resistance and the heat resistance are enhanced.

[0025] In the surface layer, as described above, the force containing boron together with the hard particles is combined with the binder metal to form an iron group metal boride, and the boride precipitates between the hard particles. Existing as a phase, the iron group boride itself is hard, so that the surface layer is hardened by the contribution of the iron group boride. Borides include FeWB, NiWB, or CoWB in the presence of WC. NiWSi, CoWSi in the presence of WC

4 Including 4

As described above, the sintering tool uses WC or TiC or a mixture thereof for the hard particles, and Ni or Co for the binder metal. As an example of a tool, when the hard particles are WC and the binder metal is Co, the required amount of the internal part is determined by the fine particle phase WC phase and the metal Co phase (Co solid solution) as the main phase. The surface layer contains a WC phase, a finely precipitated CoWB phase as a boride phase (and a very small amount of a Co solid solution phase, if a Co phase is present). I have. In addition, as a silicide phase, a finely precipitated CoSi phase, a WSi layer, and a CoWSi layer are included in the surface layer.

2 2 4

[0027] The surface hardness of the WC-Co-based sintered tool of the present invention also depends on the hardness of the internal part, but it is higher than the Vitzkers hardness of Hv700, especially HvlOO, usually higher than the surface hardness of the internal part. , Hvl40 Those having a range of 0 to 1800 or higher, for example, having Hv2300 are preferred.

[0028] In general, the thickness of the surface layer portion is defined as a distance from a linear portion of the hardness distribution curve from the surface to the inside toward a position where the average hardness of the internal portion is reached, and the thickness of the surface portion is 2 mm or more. , Preferably, 4 mm or more.

[0029] In this way, the surface layer portion of the present invention achieves surface hardening due to the densification of hard particles and the coexistence of iron group metal boride, and the internal portion is formed by the hard particles and the binder metal. The required toughness, hardness and strength can be ensured by the blending of.

[0030] Regarding the method for manufacturing a sintered tool of the present invention, first, a sintered body is produced. The sintered body is formed into a desired shape by compression molding a mixed powder of hard particles and an iron group binder metal. The green compact is then formed into a normal sintered body by ordinary liquid phase sintering. Thereby, a dense and uniform sintered body is obtained. This sintering method is entirely sintered using a conventional method. After sintering, the sintered body can be appropriately machined such as cutting, grinding, and electric discharge machining into a desired shape.

Next, on the surface of the sintered body, a boron or silicon coating layer is formed on the surface. This kind of coating layer is coated with a boron coating agent containing boron, and in the heat treatment, the sintered body having the boron coating layer is heated to form a surface layer portion rich in boron or silicon. is there.

[0032] In this heat treatment, the sintered body having the boron coating layer is cooled in a vacuum or an inert gas atmosphere, preferably a nitrogen gas atmosphere, to a temperature lower than the liquidus temperature in the internal body of the sintered body. Heating and holding for a desired time in a temperature range higher than the eutectic temperature of the boron-containing phase in the sintered body. During the heat treatment, the boron in the boron coating layer is diffused from the surface of the sintered body into the interior to form a boron-rich surface layer, and the melt in the surface layer is diffused and moved to the inner part, and the sintered body is diffused. The distribution density of the hard particles in the surface layer portion is made higher than that in the inner portion, and after cooling, boron or silicon is precipitated on the surface portion as a boride containing noinder metal and Z or a silicide phase, A sintered tool having a hardened surface layer is obtained.

[0033] As to the details of the method for producing a sintered tool of the present invention, as described above for the sintered tool, the hard particles include carbide, nitride or carbonitride, and particularly as carbide. , WC, TiC, TaC, NbC, VC, Cr C, TiN, TaN, NbN, VN, Cr N as nitride

2 3 2

, ZrN force At least one or two or more are used. The other binder metal is at least one selected from iron group metals, that is, Fe, Ni, and Co. Preferably, Ni and Co can be used.

[0034] When Ni or Co as a binder metal contains B or Si, it becomes Ni—B or Ni—Si alloy or Co—B or Co—Si alloy! / — And Ni—W—B or Ni— Since the eutectic temperature of the W—Si alloy or Co W—B or Co—W—Si alloy is lower than the solidus temperature of the alloy system of M or Co and the above carbide, Ni—W—B or Ni — W—Si alloy or Co— W—B or Co—W—Si alloy is used for heat treatment to harden the surface by making the distribution of hard particles in the surface layer higher than the inner part as described later. Used for

[0035] The ratio of the content of the hard particles to the content of the binder metal in the raw material of the hard particles and the powder of the binder metal raw material is preferably in the range of 5:95 to 30:70. The ratio of this content is selected depending on the use of the sintering tool. However, in general, in the use requiring toughness, particularly impact resistance, together with the surface hardness, the above-mentioned compounding range is used. Among them, hard particles are reduced and the content ratio of the binder metal is increased. On the other hand, for applications requiring particularly high surface hardness and abrasion resistance, the content ratio of the hard particles is increased within the above range.

[0036] The raw material hard particles preferably have an average particle diameter in the range of 0.2 to 15 m, and more preferably in the range of 0.5 to 10 m.

[0037] By using the above raw material hard particles, sintering and heat treatment can obtain the particle size of the surface layer portion and the internal portion of the product tool. The average particle size of the hard particles in the tool is in the range of 0.2 to 15 m in average particle size. As described above, the finer the hard particles, the greater the surface hardness. If the force is smaller than 0, the change in the amount of bound carbon and nitrogen in the hard particle phase increases, and the stability in terms of surface hardness is increased. Cannot be maintained. On the other hand, if it exceeds 15 m, it is better to avoid it because wear resistance is reduced. The particle size of the surface layer portion and the internal portion varies depending on the use of the tool * shape, but in particular, the range of 0.5 to 10 m in average particle size is more preferably used.

[0038] The mixed powder of the hard particles and the binder metal is compression-molded into a green compact having a desired shape, and the green compact is sintered similarly to a conventional sintered component. For sintering, perform main sintering after preliminary sintering. Although a dense sintered body is obtained, conventional liquid phase sintering can be applied, for example.

[0039] In the boron or silicon coating step of the present invention, a coating material containing boron or silicon is applied to the surface of the sintered body. The boron coating material for this purpose contains a boron compound and oxidizes boron. Materials, nitrides or carbides, or precursors thereof, for example, carbonates and hydroxides. For example, SiB, BN, BC, BO, HBO, borane, or organoboron

6 4 2 3 3 3

Compounds and the like can be used for the coating material. The silicon coating material includes a silicon compound, and includes a carbide or nitride, a boride, a precursor thereof, or an intermetallic compound. More specifically, there are Si, SiH4, SiC14, SiC, Si3N4, SiB6, or CoSi2, MoSi2, CrSi2, WSi2, or silanes, polysilane polymers, and other organic silicon compounds.

[0040] The boron coating material contains these boron compounds and coats the surface of the sintered body. The coating material may be applied directly to this surface. However, from the viewpoint of coating reliability, these coating materials are preferably used. The boron compound is suspended in water or a non-aqueous solvent to prepare a slurry-like coating solution, and applied to the surface of the sintered body. For example, a method of applying a coating liquid by brush on the surface of the sintered body, a method of spraying with a spray or the like, a method of dipping the sintered body in a coating liquid bath and pulling it up are used. Next, the coating liquid is dried on the surface of the sintered body so that the coating material is left.

[0041] The coating liquid may be applied to the entire surface of the sintered body. However, the surface to be hardened of the sintering tool is limited, and the other surface portions are appropriately masked to obtain a boride. If the coating material is prevented from being covered, the surface layer is formed only in a desired surface area by the heat treatment step, and the surface layer allows the surface of the tool to be hardened. It is relatively soft and has high toughness. The same applies to silicon.

[0042] On the other hand, as a boride or silicate coating step as another means, chloride, fluoride, or hydride or an organometallic compound is introduced into a heating furnace to be decomposed, and the surface of the sintered body is decomposed. There is also a method of vapor deposition coating. This method is generally called chemical vapor deposition [CVD]. In addition to the conventional atmospheric pressure CVD method and reduced pressure CVD method, in recent years, plasma CVD method, thermal CVD method, laser CVD method, etc. have been developed. Thus, the deposition rate by vapor deposition has been improved to 0.1 / zm / sec or more. [0043] Materials used as the raw material source at this time include, for example, boron chloride and boron fluoride, and boron fluoride and boron fluoride. The hydrides include diborane, pentaborane and dihydroborane as borohydrides (boranes) and derivatives thereof, and monosilane and disilane as hydrides (silanes). Examples of the organometallic compound include an organic boron compound and an organic silicon compound, such as trialkylboron, chlorosilane, and alkoxysilane. -n-butylboron, etc., and dichloromethylsilane, chlorodimethylsilane, chlorotrimethylsilane, tetramethylsilane, etc. Other compounds include organic boronic acids.

[0044] Specifically, these compounds are made into a gaseous state, and the gaseous compounds are introduced into a heating furnace set at a furnace temperature at which the compounds can be decomposed by a predetermined flow rate of a carrier gas, and the compound is fired. A boride or a silicide resulting from the decomposition of the compound is deposited on the surface of the composite. As the decomposition / deposition reaction continues for a predetermined time, a coating metal layer having a predetermined thickness is formed on the surface of the sintered body.

The adjustment of the coating thickness at this time is controlled by gas concentration, carrier gas flow rate, heating temperature, heating time, and the like.

On the other hand, as another coating means, a dense boride-silicide metal coating is formed by spraying a boride or silicide powder agglomerate heated to a semi-molten state onto the surface of a sintered body at a high speed. Can be formed. These borides and silicides include SiB, SiC, SiN, BN, and BC.

6 3 4 4

[0046] In the heat treatment, the sintered body whose surface contains boron or silicon and is coated with the dry coating material is then heated while being held in a vacuum. The heat treatment temperature should be lower than the solidus temperature or eutectic temperature determined by the composition of the alloy system of the hard particles and the iron group noinder metal, and the sintered body composition In this case, the temperature is selected so as not to produce a melt and higher than the eutectic temperature of an alloy system containing boron or silicon from the coating layer, hard particles and a binder metal on the surface.

[0047] That is, the present invention utilizes the fact that the eutectic temperature containing boron or silicon is lower than the eutectic temperature of a sintered body not containing boron or silicon, and the heat treatment temperature is set to the eutectic temperature. The temperature is set to a certain degree, and a melt is partially formed only on the surface or the surface layer. This melt consists of the majority of boron and iron group metals and only a small portion of the hard particles, with most of the hard particles remaining solid.

From the phase diagram of the WC—Co pseudo binary alloy, the eutectic temperature is about 1320 ° C., while the Co—B series Side eutectic point, ie eutectic temperature of Co—Co B

Since 3 degrees) is about 1110 degrees Celsius, a heat treatment temperature of 1150-1310 is used, preferably for a force in the range of 1200-1300 degrees C.

[0049] For the WC-Ni-based sintered tool, from the phase diagram of the WC-Ni pseudo binary alloy, the eutectic temperature is about 1390 ° C, while the Ni-B-based Ni-side eutectic point (ie, eutectic of Ni-Ni B

3) is about 1090 ° C, so the heat treatment temperature is between 1150 ° C and 1380 ° C between the two eutectic temperatures, and the force is used for SJ IJ, preferably in the range of 1200-1370 ° C. Used for power S He IJ.

Further, since both the TiC Co-based and TiC Ni-based have a liquid phase appearance temperature of about 1270 ° C., the heat treatment temperature of the TiC—Co-based and TiC Ni-based sintered tools is 1200 — 1250 ° C is preferred. Further, since the eutectic temperature of the MoC—Ni system is about 1250 ° C,

2

In a temperature range of 1250 ° C, diffusion heat treatment of TiC Mo C—Ni can be performed.

2

In this system, the compounding power of Mo C carbides in TiC Co system or TiC Ni system

2

It is possible to suppress grain growth and improve sinterability. The appearance of the liquid phase, the formation of the conjugate, and the diffusion transfer in the heat treatment process as described above are the same for the silicon. The appearance temperature of the liquid phase on the 0-side of the 0-31 system is around 1200 ° C. In the case of ^ -31, the liquid phase appearance temperature drops below 1000 ° C at ^ -30% 31 composition.

From these facts, the temperature of silicon diffusion heat treatment for WC-Co alloys is 1250-1320. C is used, and the range of 1150-1350 ° C is used for WC-Ni alloys.

[0051] When the heat treatment is performed in the above temperature range, in the initial stage of the heat treatment, boron in the boron-containing coating layer that coats the surface of the sintered body reacts with the iron group metal on the surface, and borane on the surface. Force to form a melt containing a low temperature eutectic composition containing element However, since the interior of the sintered body does not contain boron, it remains a solid that does not melt at the processing temperature. As the heat treatment time elapses, the melt at the surface dissolves the metal inside and permeates the inside while accompanying the boron. As the melt permeates and diffuses into the interior, there is less melt near the surface. And the concentration or distribution density of the hard particles increases. The same applies to silicon.

[0052] The region where the content of boron or silicon is high and the hard particle density is high is the surface layer portion, and the surface layer portion is such that the distance between the particles adjacent to each other is small and the remaining boron or boron is small. The content of silicon also increases. After the desired treatment time, if cooled or left to cool, the surface layer forms a compound of boron or silicon and a binder metal, and a boride or a silicate is deposited. The surface layer constitutes a layer composed of borides or silicates and hard particles having a high distribution density.However, in this manufacturing method, the hard particles in the surface layer hardly grow and are densified. , Surface hardening can be realized.

[0053] The content of boron or silicon in the surface layer after heat treatment is controlled by the type of boron or silicon compound in the coating material before heat treatment and the amount of boron or silicon coating per surface area of the sintered body. Can be. For example, the amount of boron in the boron coating layer is preferably in the range of 5.0 to 40 mgZcm ² with respect to the coated surface in terms of the metallic boron B element. In this range, the surface layer portion can contain boron B in the range of 0.050-0.50% by weight as described above. At the surface, this high content of boron is due to the fact that boron is present as a compound of the iron group metal. The same applies to silicon.

When the production method of the present invention is applied to a WC—Co-based sintered tool, the surface hardness also depends on the hardness of the internal part. Hv700 or more, especially HvlOOO or more, usually in the range of Hvl400-1800, or more, for example, Hv2300, which is preferred! / ヽ.

[0055] In general, the thickness of the surface layer portion is 3 mm or more, assuming that it is the distance from the surface to the inside of the hardness distribution curve in a straight line portion to the position at which the average hardness of the internal portion is reached. Preferably, 6 mm or more can be secured.

[0056] The sintered tool of the present invention can be widely applied to cutting tools, plastic working tools, rock drill bits for mining and civil engineering construction, and the like.

[0057] Examples of cutting tools include single tool blades, milling cutters, and drills and reamers. Drills and reamers are hard particles with a particle system of 1.0 m or less, a sintered body of ultra-fine particles. Since the shape has a high ratio of the length D to its diameter D (LZD ratio), a material with high toughness is required. High hardness and fine braid By weaving, the surface layer has high hardness, which is advantageous for the configuration of the cutting edge, and the tool life can be increased.

Examples of the working tool include a press die, a forging die, a punch, and the like, and the sintered tool of the present invention can be applied to these. For example, molds for cans have conventionally been made of ceramic materials or Ni-based superalloys.However, ceramics cause surface defects and superalloys are difficult to prepare the metallographic structure immediately. According to the present invention, the WC—Co-based sintered body is subjected to boron diffusion heat treatment to increase the distribution density of hard particles containing boron, thereby obtaining high hardness, high wear resistance, and high adhesion resistance. In addition, due to the corrosion resistance, a mold having a long mold life can be obtained.

[0059] The processing tool also includes a drawing die for steel pipes and a plug for drawing. Conventional cemented carbide has a problem of seizure. To prevent seizure, the surface of the cemented carbide is coated with TiN. However, by performing boron diffusion heat treatment using WC Co as a sintering tool of the present invention as soon as seizure occurs, CoWB (or Si) on the surface layer reduces the friction coefficient. As a result, the adhesion resistance is improved, and the life of the tool can be extended.

[0060] Examples of other processing tools include a hot extrusion die for an aluminum alloy, and the die is formed by using the sintered tool of the present invention in place of the conventional steel for hot forming, thereby increasing the extrusion temperature. At around 500 ° C, in the presence of CoWB or CoWS in the surface layer, adhesion resistance is improved and die life can be improved.

[0061] Furthermore, the cold forging punch for backward extrusion is used under severe conditions in which the frictional force with the work material with a large compression load is extremely high. Here, the present invention can be applied to prevent a breakage accident due to insufficient punch toughness, reduce seizure wear of a bearing portion of the punch, and improve tool life.

Example 1

[0062] A commercially available tungsten carbide WC powder having an average particle size of 1.5 µm and a metal cobalt Co powder of 1.3 m were mixed, and 10% contained in WC and 20% contained in WC And two types of mixtures with Co. The mixed powder is compression-molded, and the green compact is intermediately sintered, After being formed into a shape having a size of 30 mm in diameter and 30 mm in length after sintering, liquid phase sintering was performed at 1400 ° C. for 1 hour in a vacuum to obtain each sintered material.

Next, boron carbide BC is used as a boron source for the heat treatment to prepare a boron-containing coating material.

Four

For commercial production, commercially available boron carbide B C was ball-milled with ethanol for 30 hours.

Four

It was ground to prepare a slurry containing 9% of BC. Add polyethyleneimine to the slurry,

Four

A boron-containing coating liquid for coating was used.

[0064] The sintering material is immersed in a coating solution and then taken out using an immersion method as a coating method.

The sample was dried in a drier at ° C.

As a comparative example, the above sintered material was used as it was without applying a boron-containing coating material.

Diffusion heat treatment was performed on the above-described example samples and comparative example samples under the following conditions. The sample is held in a vacuum furnace, the furnace pressure is controlled to 40-80 Pa, and the sample is heated at a heating rate of 5 ° C, min, and heat treated at three levels of 12,000 ° C, 1250 ° C, and 1280 ° C. The temperature was maintained for 3 hours, diffusion heat treatment was performed, and the furnace was ordered later.

[0066] The heat-treated sample was cut at a position of 15 mm in length, the cut surface was polished, and the cross-sectional structure was observed with a microscope. Hardness was measured.

[0067] Boron-coated WC- 20% Co sintered tool, using fine hard particles (particle diameter 1-2m), dipped in 9% BC coating solution and coated And diffusion heat treatment with boron

Four

As shown in FIG. 1 (A), the cross-sectional structure of the sample showed many clear white metallic Co phases in the WC particles in the structure photograph of the internal part. FIG. 1 (B) shows a dense carbide WC indicating the structure of the surface layer of this sample, and almost no white metal phase is observed. A comparison of these structures shows that the metallic Co phase near the surface migrated to the inside during the heat treatment process.Comparing Fig. 1 (A) and Fig. 1 (B), In both cases, there was almost no difference in the particle size of the WC particles.

[0068] Similarly, by using coarse hard particles (particle diameter 3-6 μm) of WC—20% Co composition,

Fig. 2 (A) shows a microstructure photograph of the cross-sectional structure of the solid part and the surface layer part of Fig. 2 (B) of the sintered body that was coated by dipping in 9% coating solution of 4 and subjected to diffusion heat treatment with boron. Shown in the comparison From this figure, it can be seen from the figure that the surface layer (Fig. 2 (B)) becomes a whiter phase in the binder metal phase (Fig. 2 (A)) than the inner part (Fig. 2 (A)) in the diffusion heat treatment. It can be seen that the particle diameter of the hard particles (WC particles) hardly changed in both cases.

[0069] On the other hand, the structure of the untreated comparative example showed no significant structural change similar to Fig. 1 (A) both in the surface layer and inside.

Next, the hardness measurement results are shown in Table 1 and FIG. As is clear from the figure, a clear gradient was observed in the hardness distribution of the coating material. Within the above heat treatment range, the lower the temperature, the higher the surface hardness and the smaller the thickness of the surface layer. When the heat treatment temperature is increased, the diffusion of the melt into the interior proceeds, and the hardness of the surface having a relatively thick surface layer tends to decrease. That is, the difference in hardness between the surface layer and the internal part is about HV = 300-600, the heat treatment temperature is higher, and the sample has a greater gradient depth! /.

[0071] Table 1

[0072] The gradient region of hardness is also a diffusion region of boron B, and it is considered that the internal diffusion of boron B progressed by increasing the heat treatment temperature. The main reason for the improvement of the surface layer hardness is that the distance between the particles on the surface layer side is reduced due to the decrease in the surface layer metal phase, and that the hardness improvement effect due to the formation of CoWB also contributes. Conceivable. As for the untreated product, of course, almost uniform hardness distribution was obtained.

[0073] A sample having a thickness of 2mm in the surface layer was cut out, and the boron B content was measured by an ICP-MS method. Example 2

[0074] Using the sintered material prepared in Example 1, the BC slurry concentration was set to 9%, 18%, and 24%.

Four

Coating with 3 levels of coating conditions, heat treatment conditions: heating rate 5 ° CZmin, heat treatment The heat treatment was performed at a temperature of 1280 ° C. for 3 hours.

[0075] After the obtained sample was cut and polished at the center, the cross-sectional structure was observed, and then the surface force was varied in depth, and the hardness was measured by a Vickers hardness tester. The results are shown in Table 2 and FIG.

[0076]

Table 2

[0077] Referring to Table 2 and Fig. 4, it can be seen that WC-10% Co and WC-20% Co using tungsten carbide WC powder having a particle size of 1.5 µm were both compared with those in Example 1. It can be seen that the diffusion depth is as large as 2-5 mm, and the diffusion depth increases in proportion to the coating material concentration.

[0078] As described above, it is found that by setting the conditions of the coating material concentration, that is, the amount of boron to be added to the surface, and the heat treatment temperature, an appropriate hardness distribution can be obtained in the surface layer portion.

[0079] With respect to the sample heat-treated in Example 2, the force of X-ray diffraction of the surface layer was not shown, but a diffraction peak corresponding to CoWB was observed in the diffraction chart. From this, it is considered that the effect of the hard boride particles contributed to the improvement of the hardness of the surface layer.

Example 3

Next, commercially available WC powder having an average particle size of 0.55 μm, metal Co powder, chromium carbide Cr C powder, and vanadium carbide VC powder also having an average particle size of 1.3 μm And mix

3 2

Then, a mixed powder having a composition of WC-20% Co-0.7% Cr-0.4% V was prepared and compacted to obtain a compact. In the same manner as in Example 1, the green compact was subjected to intermediate sintering, then cut into a cylindrical body having a diameter of 30 mm and a length of 30 mm, and similarly subjected to vacuum sintering at 1350 ° C for 1 hour and tested. Sintering material.

As the boron coating material, a slurry-like coating liquid containing boron carbide B and C was used as in Example 1.

Four

Power In addition, commercially available hexagonal boron nitride (h-BN) is mixed in ethanol for 30 hours. The resulting 9% h-BN slurry was polished with polyethyleneimine to obtain a coating liquid for BN coating.

[0082] The above-mentioned sintered material was subjected to two types of coating, that is, coating with a BC-containing slurry and, separately, coating with a BN-containing slurry-like coating solution. On the other hand, the sintered material of WC-10% Co and WC-20% Co prepared in Example 1 was subjected to BN coating. After drying, each sample was subjected to a diffusion heat treatment at 1280 ° C for 3 hours.

[0083] The hardness of the heat-treated sample was measured with a Vickers hardness meter while changing the surface force depth. The results are shown in Table 3 and FIG.

[0084] Table 3

[0085] Table 3 and Fig. 5 show that in the sample WC—20% Co—0.7% Cr—0.4% V using WC powder with an average particle size of 0.55 m belonging to the ultrafine particle system, With the BC coating treatment, the surface layer hardness has reached HV hardness of 2050, indicating the effect of diffusion heat treatment.

[0086] Both the BN-coated WC-10% Co and the WC-20% Co have a diffusion depth of 3-4 mm, which is smaller than that of Example 1, and the surface layer hardness is lower. You can see that it is. This is considered to be due to the fact that h-BN is a compound that is stable at high temperatures and therefore does not easily react with the metal phase.

Example 4

[0087] Here, as the metal vapor deposition coating step, a metal salt shading product, 3 salt shading boron [BC1],

An example using [CH], hydrogen] will be described.

4 2

The CVD apparatus shown in FIG. 6 was used. 3 Gas of boron chloride [BC1] and methane [CH], hydrogen]

3 4 2 The prepared gas is supplied to the heating furnace 1 from the cylinders 11, 12, and 13 via the flow meter 3 and the regulating valve 4. A water ring pump 2 is connected to the heating furnace 1 so that the inside of the heating furnace can be set to a desired reduced pressure. In this heating furnace 1, the two kinds of The sintered body was set and subjected to CVD treatment under the chemical vapor deposition conditions shown in the table below. The thickness of the BC film on the surface of the sintered body after the treatment was confirmed to be about 12 to 15 m.

Four

In this embodiment, a desired coating layer thickness can be obtained by using a thermal CVD method or a laser CVD method in order to further increase the film thickness by the low pressure CVD process.

Four

Item Condition

B C 15 1%

C H 5 o 1%

H ₂ remaining o 1%

Reaction temperature 100-120 ° C

Gas flow rate 10? / Min

Reaction time: 5 hours The above coating layer was confirmed to have a predetermined diffusion heat treatment effect by the same heat treatment as in Examples 13 to 13.

Example 5

Since the cemented carbide used in general warm and hot regions has a WC average particle size of 3 μm or more, the so-called medium-grain force was evaluated using WC powder in the coarse-grain region.

Using commercially available 5.7 m average particle size WC powder, 1.3 m Co powder, 1.5 m Ni powder and Cr-C powder, WC-13% Co-2% Ni-l% Cr [15LB] and WC -18% Co-4% Ni-1.5% Cr [22HB] was prepared and mixed. After forming a green compact having the same shape as in Example 1 from the obtained mixed powder, liquid-phase sintering at 1380 ° C × 1 Hr was performed in a vacuum to obtain respective sintered materials.

Next, a coating material was prepared using silicon carbide SiC as a silicon source for the heat treatment. The method of adjustment was the same as in Example 1, and a 15% SiC-containing ethanol coating was prepared. The surface of the sintered material was coated by an immersion method, dried, and subjected to diffusion heat treatment. The heat treatment temperature was 1300 ° C X 3 Hr. In addition, the comparative evaluation was also performed on the sample as it was without coating.

The heat-treated sample was cut at a length of 15 mm, the cut surface was polished, the cross-sectional structure was observed, and then the hardness was measured with a Vickers hardness tester while changing the surface force depth. The distribution density of WC particles is up to the surface depth of about 2 mm. The internal structure was clearly higher in the amount of binder metal inside.

The results of the hardness measurement are shown in Table 4 and FIG.

Table 4

As is clear from FIG. 7, the hardness is relatively low due to the use of coarse-grained WC, but the hardness of the surface layer is remarkably increased as compared with the internal part.

The diffusion depth of silicon is smaller than that of boron diffusion material when considered as the hardness gradient part. This is thought to be due to the difference in elemental characteristics between boron and silicon. However, it was confirmed that the diffusion movement of the binder metal showed the same behavior as that of boron. The fact that is given is a feature extremely useful as a tool applied to a high-temperature region.

Also, if SiB is used as the coating material, the surface layer where both the properties of boron and silicon are combined

6

Characteristics are obtained.

Industrial applicability [0089] In the sintered tool of the present invention, the surface layer contains 0.01% to 2.0% by weight of boron B and Z or silicon Si, and contains hard particles having a higher content than the inner part. As a result, the surface layer is hardened from the internal portion, and the internal portion can secure toughness, thereby providing a tool having excellent toughness and surface hardness.

Further, the surface layer portion can substantially form a hardened surface from a hard particle phase, boron and Z or a silicon, a binder metal, a boride and a Z or a silicide phase.

[0091] While the tool has a hardened surface, the weight ratio of the iron group metal to the hard particles in the internal part can be adjusted in the range of 5:95 to 40:60. The composition can be adjusted according to.

[0092] The method for manufacturing a sintered tool according to the present invention is characterized in that, after sintering from hard particles and a binder metal, a boron coating layer is formed on a dense sintered body, and diffusion heat treatment is performed. The surface layer can be hardened while ensuring the toughness of the sintered body, and a sintered tool having surface hardness and toughness can be provided.

[0093] In particular, the production method is to prepare a sintered body into a desired shape, and then heat-treat the surface while the internal portion remains solid, thereby polishing the surface layer where the dimensional change of the heat-treated product is small. Since the amount is small, it can be used as a tool without reducing the hardness of the surface layer.

Claims

The scope of the claims

[1] Hard particles containing hard carbide, nitride or carbonitride, iron group metal as binder metal, and sintered sintered tool

The sintering tool has a surface portion containing boron B and / or silicon Si in a range of 0.010 to 2.0% by weight, and the surface portion has a higher distribution density than the inner portion. A sintered tool characterized by having hard particles.

[2] The surface layer substantially comprises a hard particle phase, a boride and a Z or a silicide phase, which are compounds of boron and Z or silicon carbide and a binder metal, and is formed by a sintering tool. 2. The sintered tool according to claim 1, wherein the inner portion inside the surface layer portion substantially comprises a hard particle phase and a binder metal phase.

[3] The sintered tool according to claim 1 or 2, wherein the content by weight of the iron group metal and the hard particles in the internal part is in the range of 5:95 to 40:60.

[4] Noinder metals include Co or Ni,

Claim 2 or 3 wherein the boride and Z or silicate phases of the surface layer contain Co or Ni.

3. The sintering tool according to 3.

[5] Binder metal content force in the range from surface surface to depth 0.5mm

The sintered tool according to claim 1, wherein the content is 2% or less.

[6] The sintered tool according to any one of claims 1 to 5, wherein the surface layer has a smaller average distance between hard particles adjacent to each other than the inner part.

[7] The particle diameter distribution of the hard particles in the surface layer part is substantially the same as that of the inner part,

6. The sintered tool according to any one of the above.

[8] A method for manufacturing a sintered tool formed by sintering hard particles and an iron group binder metal is described.

, Manufacturing method,

Compression molding a mixed powder of the hard particles and the iron group binder metal into a green compact having a desired shape, and then sintering the green compact to form a sintered body;

Forming a boron and Z or silicon coating layer on the surface of the sintered body; and forming the sintered body having the boron and Z or silicon coating layer in a vacuum or in an inert gas atmosphere. The temperature is lower than the liquidus temperature of the sintered body, and boron and Heat treatment at a temperature required to form a melt containing zirconium and z or silicon;

Including

In the heat treatment process described above, boron and Z or boron or boron in the silicon coating layer are diffused into the surface layer of the sintered body, and the boron and z or silicon-containing melt in the surface layer is diffused. A method for manufacturing a sintered tool, characterized by diffusing and moving into an inner part to increase the distribution density of hard particles in a surface layer of a sintered body higher than the inner part.

[9] The production method according to claim 8, wherein the surface layer contains boron B and Z or silicon in a weight range of 0.050 to 1.0%.

10. The method according to claim 8, wherein the surface layer has substantially the same particle size distribution of the hard particles as the internal part.

11. The method according to claim 8, wherein the boron and Z or silicon coating material contains at least one of oxides, nitrides and carbides of boron and Z or silicon. Production method.

[12] The power of boron and Z or silicon or silicon in the coating layer is in the range of 5.0 to 60 mg / cm ² with respect to the coated surface in terms of boron metal and Z or silicon element. 8 9 1 The production method described in IV.

[13] The coating layer forming step includes: a) coating the surface of the sintered body with a coating agent containing boron and Z or silicon; or b) coating the sintered body with boron or silicon chloride, fluoride, The ability to heat the hydride or organometallic compound in a gas stream to vapor-deposit and coat boron or silicon on the surface of the sintered body, or c) the boron or silicon heated to a semi-molten state on the sintered body. 9. The method for producing a sintering tool according to claim 8, which is a process capable of spraying a compound to coat the surface of the sintered body with boron or silicon.