JP2013053022A - Composite sintered body and composite sintered body tool using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite sintered body excellent in wear resistance and chipping resistance.SOLUTION: The composite sintered body contains 60 vol.% or more and 99.7 vol.% or less of SiAlON and the rest of binder. The binder contains TiAl compound. The structure of the binder has noncontinuous parts. In is preferable that the binder further contains TiSi compound, TiN, SiN, and AlO. It is preferable that the major diameter of the particle size of 10% or more and less than 95% of the binder of the binder contained in the composite sintered body is 5 μm or less.

Description

  The present invention relates to a composite sintered body and a composite sintered body tool using the same, and more particularly to a composite sintered body excellent in fracture resistance and wear resistance and a composite sintered body tool using the same.

  Since cutting tools have different required performances such as wear resistance and fracture resistance depending on the type and processing method of the work material, different cutting tools are used depending on the requirements. For example, in applications that require fracture resistance, such as high-efficiency machining and interrupted machining, use cemented carbide tools with excellent fracture resistance, and finish Ni-base heat-resistant alloy-based difficult-to-cut materials such as Inconel. In applications where wear resistance is required, such as machining, SiAlON ceramic tools and cBN sintered body tools with excellent wear resistance are used.

  As described above, the cutting tool is selected to cope with various cutting processes, but there is a case where a suitable cutting tool corresponding to the work material has not been developed. As an example, for example, a cutting tool for cutting difficult-to-cut materials having a hardness of more than 40 in Rockwell C scale hardness (HRC) can be cited.

  To cut the difficult-to-cut materials, it is expected that a tool with excellent fracture resistance is preferable, but when cutting with a cemented carbide tool with excellent fracture resistance, the tool is plastically deformed. There is a problem of doing. Further, when the above difficult-to-cut agent is cut using a cBN sintered body, the iron group metal (Ni, Co, etc.) in the cBN sintered body is in the work material when the cutting edge at the time of cutting becomes high temperature. It reacts with other iron group metals and tends to cause wear and defects. Therefore, the cutting of the above-mentioned difficult-to-cut material has to rely on a SiAlON ceramic tool whose fracture resistance is not necessarily sufficient.

  By the way, in plastic working applications such as punches and dies, the use of tools using SiAlON ceramics with excellent wear resistance is advancing, replacing high-speed steel tools and cemented carbide tools. It is expected as a material.

As described above, SiAlON ceramic tools are used for cutting difficult-to-cut materials and plastic working. In the commercially available SiAlON ceramic tool, since the glass phase of Y ₂ O ₃ is continuously present as a binder phase, stability against defects is not sufficient, and further improvement is expected.

As an attempt to improve the SiAlON ceramic tool, for example, Japanese Patent Application Laid-Open No. 08-337477 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2006-175561 (Patent Document 2) include SiAlON sintered body particles as a main component. A tool made of SiAlON ceramics is disclosed in which the remainder is filled with a grain boundary phase composed of an oxide or glassy phase (amorphous phase). Also, Japanese Patent Laid-Open No. 2005-212048 (Patent Document 3) discloses a SiAlON ceramics product in which SiAlON sintered body particles are bonded to each other by a glassy phase (amorphous phase) and a metal alloy such as Si ₂ W or MoSi ₂ . A tool is disclosed.

Japanese Patent Laid-Open No. 08-337477 JP 2006-175561 A Japanese Patent Laid-Open No. 2005-212048

  Although all of the sintered body tools disclosed in Patent Documents 1 to 3 can improve the wear resistance, the fracture resistance is not sufficient, and further improvement in the wear resistance is required. The present invention has been made in view of the current situation as described above, and an object thereof is to provide a composite sintered body having excellent wear resistance and fracture resistance.

  The present inventors have observed damage on the wear surface of a commercially available SiAlON sintered body tool. As a result, the wear of the binder part has advanced in advance, and some SiAlON sintered body particles have fallen off. Was confirmed. From this result, it is surmised that the progress of wear of the SiAlON sintered body tool proceeds such that the wear of the binder selectively proceeds, and then the SiAlON sintered body particles around the binder fall off. . Therefore, the reason why the conventional SiAlON sintered body and the SiAlON sintered body tools disclosed in Patent Documents 1 to 3 are likely to be worn is that a binder having low hardness is continuously present in the sintered body. Conceivable.

Based on the above considerations, the inventors of the present invention have completed the present invention by earnestly studying the composition of the binder and the skeleton structure. That is, the composite sintered body of the present invention contains 60% by volume or more and 99.7% by volume or less of SiAlON, the balance is made of a binder, the binder contains a TiAl compound, and the structure of the binder is: It is characterized by having a discontinuous portion. The binding material preferably contains four kinds of compounds of TiSi compound, TiN, Si ₃ N ₄ and Al ₂ O ₃ .

  Of the binders included in the composite sintered body, the major axis of the particle diameter of the binder of 10% or more and less than 95% is preferably 5 μm or less. The SiAlON is preferably one or more crystal structures selected from the group consisting of α-SiAlON, β-SiAlON, ortho-SiAlON, and c-SiAlON. The binder is preferably made of only a TiAl compound. The ratio of Ti contained in the TiAl compound is preferably 15 atomic% or more and 95 atomic% or less. The present invention is also a composite sintered body tool that includes the above composite sintered body in at least a part involved in cutting or plastic working.

  The composite sintered body of the present invention has an effect of being excellent in wear resistance and fracture resistance by having the above-described configuration.

<Composite sintered body tool>
The composite sintered body tool of the present invention includes the composite sintered body of the present invention in at least a part involved in cutting or plastic working. Such composite sintered body tools are extremely useful as, for example, drills, end mills, milling or turning cutting edge-replaceable cutting tips, metal saws, gear cutting tools, reamers, taps, or crankshaft pin milling inserts. It can be usefully used. By using the composite sintered body of the present invention for a cutting edge of a tool or the like, it exhibits excellent performance that it is less likely to be damaged and is not easily worn even when cutting difficult-to-cut materials such as stainless steel, inconel and titanium. The composite sintered body tool of the present invention is superior not only in cost performance but also in wear resistance and fracture resistance as compared with the cBN sintered body tool.

<Composite sintered body>
The composite sintered body of the present invention contains 60% by volume or more and 99.7% by volume or less of SiAlON, the balance is made of a binder, and the binder contains at least a TiAl compound, and the structure of the binder is discontinuous. It has the characteristic part. The binding material preferably further includes four types of compounds of TiSi compound, TiN, Si ₃ N ₄ , and Al ₂ O ₃ . Here, “the structure of the binder has a discontinuous portion” means that the binder is arranged at intervals or bonded when the cross section of the composite sintered body is observed with a scanning electron microscope. This means that SiAlON particles are present between the materials, and the binding materials are not in contact with each other when viewed two-dimensionally. By disposing the binders discontinuously in this manner, the wear of the binder having low strength is less likely to proceed, and the wear resistance of the composite sintered body can be improved.

<SiAlON>
SiAlON contained in the composite sintered body of the present invention is characterized by being 60 volume% or more and 99.7 volume% or less. By including SiAlON at such a volume ratio, SiAlON particles grow neck-to-neck, a SiAlON skeleton structure is formed, and the hardness of the composite sintered body can be increased. In addition, the structure of the binder having low hardness has a discontinuous portion, and the toughness of the composite sintered body can be improved.

  When the volume ratio of SiAlON is less than 60% by volume, the structure of a binder that easily wears is continuous, so that there is a high possibility that the wear resistance is significantly reduced. On the other hand, if the volume ratio of SiAlON exceeds 99.7% by volume, the hardness of the composite sintered body itself can be improved, but the proportion of the binder occupying the composite sintered body is too small, and the SiAlON particles are not separated. The bond strength cannot be increased. In addition, even if only the SiAlON particles are sintered without using a binder and the SiAlON particles are bonded to each other, the bonding force is insufficient, and even if the bonding is possible, the defect resistance is insufficient. There is.

  The crystal structure of the SiAlON includes one or more crystal structures selected from the group consisting of α-SiAlON, β-SiAlON, ortho-SiAlON, and c-SiAlON. The higher it is, the better. Thereby, the cutting performance of the composite sintered body of the present invention, particularly the wear resistance, can be improved.

<Binder>
In the present invention, the binder contained in the composite sintered body contains at least a TiAl compound, and the structure of the binder has a discontinuous portion. The binding material preferably further includes four types of compounds of TiSi compound, TiN, Si ₃ N ₄ , and Al ₂ O ₃ . A composite sintered body containing a TiAl compound as in the present invention has much more excellent wear resistance and fracture resistance than a composite sintered body made of only SiAlON particles. Here, the “TiAl compound” means a TiAl alloy such as TiAl ₃ , Ti ₃ Al, or TiAl, a nitride of TiAl, or the like, and the “TiSi compound” means a TiSi alloy such as TiSi ₂ or TiSi, or TiSi. Means nitride and the like. As a factor that can improve the performance in this way, the binder containing the TiAl compound not only plays a role of increasing the bonding force between the SiAlON particles, but also has excellent toughness, and the neck growth between the SiAlON particles. This is considered to be due to the fact that the promoting effect is also exhibited. Even if a binder made of Y ₂ O ₃ is used as in the prior art, the effect of remarkably improving the wear resistance and fracture resistance as described above cannot be obtained. This is because Ti and Al contained in the TiAl compound, and Ti and Si contained in the TiSi compound are both highly compatible with SiAlON, especially Ti is highly compatible with SiAlON, but this Ti coexists with Al or Si. This is because it is considered that the interdiffusion between SiAlON particles is promoted to increase the bonding force. Therefore, the ratio of Ti contained in the TiAl compound is preferably 15 atomic% or more and 95 atomic% or less. When the atomic ratio of Ti is less than 15 atomic%, diffusion is difficult to occur, which is not preferable. When it exceeds 95 atomic%, the interdiffusion promoting action between the TiAl compound and the SiAlON particles due to Al decreases due to the small amount of Al. Therefore, it is not preferable.

Here, the TiAl compound, TiSi compound, TiN, Si ₃ N ₄ and Al ₂ O ₃ compound are preferably contained in an amount of 50% by volume or more based on the total amount of the binder. In the present invention, the remainder of the binder is a group IVa element, a group Va element, a group VIa element transition metal element, Al, Si, B, Co, Ni, C, N, O, and inevitable impurities in the periodic table. May be included.

  Further, of the binders included in the composite sintered body, the major axis of the particle diameter of 10% or more and less than 95% of the binder is preferably 5 μm or less, more preferably 20% or more and 90% or less. The major axis of the particle diameter is 5 μm or less. Here, the “major axis of the particle diameter of the binder” is the diameter of a virtual circle in which the binder particles are included when the cross section of the composite sintered body is observed with a scanning electron microscope.

  By including a binder having a major axis of particle size of 5 μm or less at such a ratio, the contact area of the grain boundary at the time of filling the SiAlON particles can be increased, the bonding force can be remarkably increased, and the crack generation mechanism is different. Crack propagation resistance can also be increased by forming a structure in which SiAlON particles composed of fine particles and coarse particles, and binder particles are mixed. When the length of the particle diameter exceeds 5 μm, the effect of improving the crack propagation resistance is reduced when the binder is less than 10% or 95% or more.

<Manufacturing method>
As a method for producing a composite sintered body of the present invention, first, mixed powder is prepared by putting SiAlON particles and TiAl particles in a cemented carbide ball and mixing them and ball mill mixing. Here, it is preferable to use SiAlON particles having an average particle diameter (D50) of 1 to 10 μm measured with a laser diffraction / scattering type particle size distribution measuring device, and TiAl particles have an average particle diameter (D50) of 0. It is preferable to use one having a thickness of 1 to 10 μm. The SiAlON particles and TiAl particles described above may be bonded to each other or dissolved and infiltrated by sintering, which will be described later. Therefore, the particle diameter may be increased or decreased.

Next, the mixed powder is filled in a high melting point container such as a cemented carbide and pressed to a pressure of 3 to 5 GPa, and then sintered at a temperature of 1200 ° C. to 1700 ° C. for 1 to 120 minutes. Thus, it is preferable to produce a composite sintered body. In addition to the manufacturing method as described above, for example, SiAlON powder is layered, and a metal plate made of Ti, Al, or TiAl compound is stacked thereon and sintered while infiltrating the TiAl melt. Thus, a composite sintered body can be produced. When the TiAl compound exceeds 50% by volume with respect to the total amount of the binder, the fracture resistance of the composite sintered body can be increased by sintering at less than 1400 ° C. On the other hand, when the binder is made of TiAl compound, TiSi compound, TiN, Si ₃ N ₄ , and Al ₂ O ₃ , it is excellent in the balance of wear resistance and fracture resistance by sintering at 1400 ° C. or higher. It will be.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Examples 1-5 and Comparative Examples 1-2>
First, β-SiAlON in which the average particle diameter of primary particles is 5 μm and TiAl particles (Ti-50 atomic% Al) having an average particle diameter of 5 μm are shown in “SiAlON volume ratio” in Table 1. A mixed powder was obtained by ball mill mixing in a cemented carbide ball at a blending ratio. Next, the above mixed powder is filled into a cemented carbide container and sintered at a pressure of 6.0 GPa and a temperature of 1390 ° C. for 30 minutes, whereby the composite sintered bodies of Examples 1 to 5 and Comparative Examples 1 and 2 are obtained. Three each were prepared.

  When the EDS analysis was performed on the composite sintered bodies of Examples 1 to 5 and Comparative Examples 1 and 2, in each sample, in addition to SiAlON, a TiAl compound and a trace amount of W, Si, Al, Ti, A reaction product with Co was identified.

  The composite sintered bodies of Examples 1 to 5 and Comparative Examples 1 and 2 were polished, and the polished surface was observed using a scanning electron microscope (SEM), and wavelength dispersion X-ray analysis attached thereto. (EPMA: Electron Probe Micro-Analysis) is used to identify the SiAlON and binder component in the cross section of the composite sintered body. In the reflected electron image with a field of view of 5000 times, the binder component exists continuously. If the binder component is divided by SiAlON, “Discontinuous” appears in the “Binder texture” column of Table 1. "

  Next, the percentage of the area ratio of SiAlON was calculated by image processing for the backscattered electron image of a region including 100 or more binder particles. As a result, the blending ratio of the above raw materials and the volume ratio of the respective compositions constituting the finally obtained composite sintered body could be regarded as the same. Although the volume ratio of the binder is not described in Table 1, it corresponds to a portion excluding SiAlON, and is a value obtained by subtracting the volume ratio of SiAlON from 100 volume%.

<Comparative Examples 3-6>
For Comparative Examples 3 to 6, the following sintered bodies were used.
Comparative example 3: Commercial SiAlON ceramics using Y ₂ O ₃ binder Comparative example 4: Commercial cBN sintered body using TiN binder Comparative example 5: Commercial cBN sintered body comparison using Co binder Example 6: Commercially available cemented carbide Vickers hardness was measured for the composite sintered bodies of Examples 1 to 5 and Comparative Examples 1 to 6, and the results are shown in the "Hardness" column of Table 1. Further, fracture toughness values (indentation method) were measured for the composite sintered bodies of Examples 1 to 5 and Comparative Examples 1 to 6, and the results are shown in “Fracture toughness values” in Table 1.

<Cutting test>
Cutting chips provided with the composite sintered bodies of Examples 1 to 5 and Comparative Examples 1 to 6 in portions involved in cutting were produced. This chip shape is classified as CNGA120408 by ISO model number, and the cutting edge processing is a chamfer shape with an angle of -25 ° and a width of 0.15 mm, the cutting edge inclination angle, the side rake angle, the front clearance angle, the side clearance angle, The front cutting edge angle and the side cutting edge angle were attached to the holder so as to be -5, -5, 5, 5, 5, and -5, respectively.

Using the cutting tool provided with the composite sintered bodies of Examples 1 to 5 and Comparative Examples 1 to 6, the tool life of the composite sintered tool was evaluated by performing continuous cutting under the following cutting conditions.
Work Material: Outer Diameter Machining of Inconel 718 Round Work Material Hardness: HRC20
Cutting speed: V = 200 m / min
Cutting depth: d = 0.3mm
Feeding speed: f = 0.12mm / rev
Coolant: Emulsion diluted 20 times The tool life is evaluated by the cutting distance (km) until the maximum wear amount (VB _max ) of the flank face of the composite sintered tool reaches 0.2 mm, and the maximum wear amount (VB _max ) In the case where a defect occurred before the thickness became 0.2 mm, the evaluation was performed based on the cutting distance until the defect occurred. The result is shown in the column of “tool life” in Table 1. Note that the longer the tool life, the better the wear resistance and fracture resistance of the composite sintered tool.

  From the results shown in Table 1, it is clear that the composite sintered tool of each example has a longer tool life than that of each comparative example. From this result, it can be said that the composite sintered body tool of each example is excellent in wear resistance and fracture resistance as compared with that in each comparative example. Thus, it is thought that the abrasion resistance and fracture resistance of the composite sintered body tool of each example were improved because the structure of the binder of the present invention had discontinuous portions.

  On the other hand, the composite sintered body tool of Comparative Example 1 was considered to be easily damaged because the binder structure was continuous. The composite sintered body tool of Comparative Example 2 had a content of SiAlON particles. It is considered that the promoting action of the binder as a catalyst was not obtained because of too much.

<Examples 6 to 12>
First, β-SiAlON having an average particle diameter of two kinds of major diameters of 1 μm and 5 μm was mixed in a cemented carbide ball at a blending ratio shown in the column “1 μm / 5 μm” in Table 2. Furthermore, TiAl particles (Ti-25 atomic% Al) having a long average particle diameter of 5 μm are formed into cemented carbide balls with a mixing ratio of 9% by volume of TiAl particles (Ti-25 atomic% Al). The mixed powder was obtained by mixing and ball milling. Next, the above mixed powder is filled into a cemented carbide container and sintered at a pressure of 6.0 GPa and a temperature of 1700 ° C. for 30 minutes, thereby producing three composite sintered bodies of Examples 6 to 12, respectively. did.

When the EDS analysis was performed on the composite sintered bodies of Examples 6 to 12, in addition to SiAlON, TiAl compound, TiSi compound, TiN, Si ₃ N ₄ and Al ₂ O ₃ and a trace amount were added in any sample. Reaction products with Al, Si, Ti, W, Co and the like were identified.

  The composite sintered bodies of Examples 6 to 12 were polished, and the skeleton structure of the binder structure was examined on the polished surface by the same method as in Examples 1 to 5. As a result, all the binders were distributed discontinuously. It became clear that. Furthermore, when the percentage of the volume ratio of SiAlON in the composite sintered body was calculated, it was revealed that it was 90% by volume. Further, the particle diameter of the binder particles of 100 points or more was measured, and the percentage of the binder particles having a major axis of 5 μm or less was calculated, and the “ratio of the binder having a major axis of 5 μm or less” in Table 2 Shown in the column.

<Comparative Examples 7-9>
For Comparative Examples 7 to 9, the following sintered bodies were used.
Comparative Example 7: Commercial SiAlON ceramics using Y ₂ O ₃ binder Comparative Example 8: Commercial cBN sintered body using TiN binder Comparative Example 9: Commercial cBN sintered body using Co binder Vickers hardness was measured for the composite sintered bodies of Examples 6-12 and Comparative Examples 7-9, and the results are shown in the column of “Hardness” in Table 2. Further, fracture toughness values (indentation method) were measured for the composite sintered bodies of Examples 6 to 12 and Comparative Examples 7 to 9, and the results are shown in “Fracture toughness value” in Table 2.

<Cutting test>
Cutting tips provided with the composite sintered bodies of Examples 4 and 6 to 12 and Comparative Examples 7 to 9 at portions involved in cutting were produced. This chip shape is classified as CNGA120408 by ISO model number, and the cutting edge processing is a chamfer shape with an angle of -25 ° and a width of 0.15 mm, the cutting edge inclination angle, the side rake angle, the front clearance angle, the side clearance angle, The front cutting edge angle and the side cutting edge angle were attached to the holder so as to be -5, -5, 5, 5, 5, and -5, respectively.

Using the cutting tools provided with the composite sintered bodies of Examples 4, 6-12 and Comparative Examples 7-9, the tool life of the composite sintered tool was evaluated by performing continuous cutting under the following cutting conditions.
Work material: Outside diameter machining of Inconel 718 round bar Work material hardness: HRC40
Cutting speed: V = 400 m / min
Cutting depth: d = 0.2mm
Feeding speed: f = 0.06mm / rev
Coolant: Emulsion diluted 20 times The tool life is evaluated by the cutting distance (km) until the maximum wear amount (VB _max ) of the flank face of the composite sintered tool reaches 0.2 mm, and the maximum wear amount (VB _max ) In the case where a defect occurred before the thickness became 0.2 mm, the evaluation was performed based on the cutting distance until the defect occurred. The result is shown in the column of “Tool life” in Table 2. Note that the longer the tool life, the better the wear resistance and fracture resistance of the composite sintered tool.

  From the results shown in Table 2, it is clear that the composite sintered bodies of Examples 4 and 6 to 12 have a longer tool life than those of Comparative Examples 7 to 9. From this result, it can be said that the composite sintered bodies of Examples 4 and 6 to 12 are superior in wear resistance and fracture resistance to those of Comparative Examples 7 to 9. Thus, it was thought that the abrasion resistance and fracture resistance of the composite sintered bodies of Examples 4 and 6 to 12 were improved because the structure of the binder of the present invention had discontinuous portions. .

  In particular, in the composite sintered bodies of Examples 8 to 10, the major axis of the particle diameter of the binder of 10% or more and less than 95% of the binders included in the composite sintered body is 5 μm or less. The improvement in wear and fracture resistance was remarkable. Further, since Example 4 was sintered at a temperature of 1400 ° C. or lower (1390 ° C.), the fracture resistance of the composite sintered body was high. On the other hand, since Examples 6 to 12 were sintered at a temperature of 1400 ° C. or higher (1700 ° C.), the composite sintered body was excellent in the balance of wear resistance and fracture resistance.

  Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Claims (6)

Containing 60% by volume or more and 99.7% by volume or less of SiAlON, the balance being made of a binder,
The binder includes a TiAl compound,
The composite sintered body has a discontinuous portion in the structure of the binder. The composite sintered body according to claim 1, wherein the binder further includes a TiSi compound, TiN, Si ₃ N ₄ , and Al ₂ O ₃ .   3. The composite sintered body according to claim 1, wherein a major axis of a particle diameter of a binder of 10% or more and less than 95% of the binder contained in the composite sintered body is 5 μm or less.   The composite sintered body according to any one of claims 1 to 3, wherein the SiAlON has one or more crystal structures selected from the group consisting of α-SiAlON, β-SiAlON, ortho-SiAlON, and c-SiAlON. .   The composite sintered body according to any one of claims 1 to 4, wherein a ratio of Ti contained in the TiAl compound is 15 atomic percent or more and 95 atomic percent or less.   A composite sintered body tool comprising the composite sintered body according to any one of claims 1 to 5 in at least a part involved in cutting or plastic working.