JP2021142575A - Diamond-coated cutting tool - Google Patents

Abstract

To provide a diamond-coated cutting tool having high adhesiveness of a diamond layer with a substrate.SOLUTION: A diamond-coated cutting tool 1 comprises a substrate 3 and a diamond layer 5 covering the surface 3A of the substrate 3. The average thermal expansion coefficient x of the substrate 3 in the range of 25°C at 600°C satisfies 3.1×10-6/K≤x≤4.0×10-6/K, and the diamond layer 5 has plural cavities 9 extending from a part contacting with the substrate 3 to a crystal growth direction. In a cut area obtained by cutting the face including the substrate 3 and diamond layer 5 using the cutting tool 1, the average interval between the centers 9A of adjacent cavities 9 is 12 μm or more but 1,000 μm or less.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to diamond coated cutting tools.

Patent Document 1 discloses a diamond-coated cutting tool having a structure in which a polycrystalline diamond layer (coating) is coated on the surface of a base material.
In this diamond-coated cutting tool, the surface roughness of the base material and the number of voids at the interface of the diamond layer are each limited to a specific range. Here, the surface roughness of the base material means the arithmetic average roughness Ra of the surface of the base material and the average length RSm of the roughness curve elements on the surface of the base material.
This diamond-coated cutting tool improves the adhesion of the diamond layer to the base material by the anchor effect by setting the surface roughness within a specific range.
In addition, this diamond-coated cutting tool reduces the residual stress caused by the difference in the coefficient of thermal expansion between the base material and the diamond layer by setting the number of voids within a specific range, and improves the adhesion of the diamond layer to the base material. It is improving.
As described above, the diamond-coated cutting tool of Patent Document 1 improves the adhesion of the diamond layer to the substrate by adjusting the surface roughness and the number of voids.

Japanese Unexamined Patent Publication No. 2011-38150

In the diamond-coated cutting tool of Patent Document 1, the number of voids is 1 × 10 ³ pieces / cm or more and 1 × 10 ⁶ pieces / cm or less. In this range, it is stated that the residual stress at the interface between the diamond layer and the substrate is relaxed.
However, in the above range, the distance between the voids at the interface between the diamond layer and the base material is narrow and the number of voids is large, so that the substantial contact area between the diamond layer and the base material becomes small. Therefore, there is a possibility that the peel resistance is insufficient.
The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a diamond-coated cutting tool having high adhesion of a diamond layer to a base material. The present disclosure can be realized in the following forms.

[1] A diamond-coated cutting tool comprising a base material and a diamond layer covering the surface of the base material.
The base material has an average coefficient of thermal expansion x at 25 ° C to 600 ° C.
3.1 × ^{10 -6} /K≦x≦4.0×10 -6 / K
The diamond layer has a plurality of voids extending in the crystal growth direction from the portion in contact with the base material.
In a cut surface obtained by cutting the diamond-coated cutting tool on a surface including the base material and the diamond layer, the average distance between the centers of the adjacent voids is 12 μm or more and 1000 μm or less. tool.

[2] The diamond-coated cutting tool according to [1], wherein the base material is composed of a silicon nitride sintered body or a sialon sintered body.

[3] The diamond-coated cutting tool according to [2], wherein the Sialon sintered body contains Al in an oxide equivalent of 2% by mass or more and 35% by mass or less.

[4] The silicon nitride sintered body contains at least one selected from Ti nitrides, carbonitrides, and carbides in a total amount of 5% by mass or more and 20% by mass or less.
The diamond according to [2] or [3], wherein the Sialon sintered body contains at least one selected from Ti nitrides, carbonitrides, and carbides in a total amount of 5% by mass or more and 20% by mass or less. Coating cutting tool.

[5] The diamond-coated cutting tool according to any one of [2] to [4], wherein the Sialon sintered body contains a polytype crystal phase.

The diamond-coated cutting tool of the present disclosure improves the adhesion of the diamond layer to the base material by setting the coefficient of thermal expansion of the base material in a specific range and setting the average distance between the centers of adjacent voids in a specific range. It can be done and the peeling resistance is improved.
Further, by using a sintered body having a specific composition as the base material, the peel resistance is further improved.
When the base material is composed of a Sialon sintered body containing a polytype crystal phase, the peel resistance is particularly excellent.

It is a figure which showed typically the SEM image of the cut surface of a diamond-coated cutting tool. It is an enlarged view of FIG. It is a figure which showed the example of the void schematically.

Hereinafter, the present invention will be described in detail. In this specification, the description using "~" for the numerical range shall include the lower limit value and the upper limit value unless otherwise specified. For example, in the description of "10 to 20", both the lower limit value "10" and the upper limit value "20" are included. That is, "10 to 20" has the same meaning as "10 or more and 20 or less".

1. 1. Diamond coated cutting tool 1
(1) Configuration of Diamond-Coated Cutting Tool 1 The diamond-coated cutting tool 1 includes a base material 3 and a diamond layer 5 that covers the surface 3A of the base material 3. The base material 3 has an average coefficient of thermal expansion x from 25 ° C. to 600 ° C. satisfying the following relational expression 1.
^{3.1 × 10 -6 /K≦x≦4.0×10 -6 / K} ··· equation 1
Further, the diamond layer 5 has a plurality of voids 9 extending in the crystal growth direction from the portion in contact with the base material 3. The average distance between the centers 9A of the adjacent voids 9 on the cut surface obtained by cutting the diamond-coated cutting tool 1 on the surface including the base material 3 and the diamond layer 5 is 12 μm or more and 1000 μm or less. ..

(2) Base material 3
(2.1) Average coefficient of thermal expansion x of base material 3
As described above, the average coefficient of thermal expansion x of the base material 3 from 25 ° C. to 600 ° C. preferably satisfies the above relational expression 1 from the viewpoint of improving the adhesion of the diamond layer 5 to the base material 3, and has the following relationship. It is more preferable to satisfy the formula 2, and it is further preferable to satisfy the following relational expression 3. The average coefficient of thermal expansion x can be measured using TMA (Thermo Mechanical Analysis).
^{3.1 × 10 -6 /K≦x≦3.7×10 -6 / K} ··· equation 2
^{3.1 × 10 -6 /K≦x≦3.4×10 -6 / K} ··· equation 3

(2.2) Preferable Configuration Example of Base Material 3 The base material 3 is preferably composed of a silicon nitride sintered body or a sialon sintered body from the viewpoint of further improving peeling resistance. _{Silicon nitride (Si 3} N ₄ ) in a silicon nitride sintered body is a crystal particle of ceramics composed of Si (silicon) and N (nitrogen), and is sintered by adding a sintering aid or the like to silicon nitride as a raw material. Will be done. Silicon nitride has an α phase having an equiaxed particle shape and a β phase having a needle-like particle shape, and the toughness and hardness characteristics can be controlled by the composition ratio of these. Since β-silicon nitride has a structure in which needle-like structures are entangled, it has high toughness, and since α-silicon nitride has an equiaxed particle shape, it has lower toughness than β-silicon nitride. High hardness. In silicon nitride contained in the silicon nitride sintered body, these crystal phase species and composition ratios are not particularly limited.

The silicon nitride sintered body refers to at least one or more elements (hereinafter, may be referred to as "specific elements") selected from the group consisting of Group 4 elements, rare earth elements and Mg (magnesium) in the periodic table. It may be contained. The content ratio is not particularly limited, and for example, it may be contained in the range of 0.5 mol% or more and less than 2.6 mol% in terms of oxide with respect to the silicon nitride sintered body. The periodic table referred to here is "Inorganic Chemistry Nomenclature-IUPAC 1990 Recommendation-" G.M. J. Edited by Leich, translated by Kazuo Yamasaki, published on March 26, 1993, published by Tokyo Kagaku Dojin Co., Ltd., according to Table I-3.2 "Designation of Group of Periodic Table".

As the Group 4 element of the periodic table, which is one of the specific elements, for example, titanium (Ti), zirconium (Zr), hafnium (Hf) and the like can be mentioned as preferable examples. Examples of rare earth elements include scandium (Sc), yttrium (Y), lanthanoids and actinides. Examples of the lantanoid include cerium group elements and ytterbium group elements, and examples of the cerium group elements include lanthanum (La), cerium (Ce), placeodium (Pr), neodymium (Nd), and promethium (Pm). , And cerium (Sm), and examples of ytterbium group elements include lutetium (Eu), gadrinium (Gd), terbium (Tb), dysprosium (Dy), formium (Ho), erbium (Er), and turium (Er). Tm), ytterbium (Yb), and lutetium (Lu) can be mentioned. Examples of the actinide include actinium (Ac) and thorium (Th). In addition, oxide conversion means to oxidize an element or convert it into an oxide bonded to oxygen.

One of the specific elements may be contained in the silicon nitride sintered body, or a plurality of types of the specific elements may be contained in the silicon nitride sintered body.

From the following viewpoints, the silicon nitride sintered body preferably contains at least one selected from Ti (titanium) nitrides, carbonitrides, and carbides in a total amount of 5% by mass or more and 20% by mass or less. It is more preferable to contain 5% by mass or more and 15% by mass or less in total, and further preferably 5% by mass or more and 10% by mass or less in total. Further peeling resistance can be expected when the silicon nitride sintered body contains the above compound of Ti (titanium) within the above range. That is, the matrix silicon nitride (α-silicon nitride, β-silicon nitride) having a coefficient of thermal expansion smaller than that of the diamond layer 5 and the above compound of Ti (titanium) having a thermal expansion larger than that of the diamond layer 5 are composited. Then, the tensile stress and the compressive stress are randomly applied to cancel each other out, and the thermal expansion of the entire sintered body is within the range of the above relational expression 1, and further peeling resistance can be expected.
Preferable examples of Ti (titanium) nitrides, carbonitrides, and carbides include TiC _x N _(1-x) (0 ≦ X ≦ 1).

Sialon (SiAlON) in the Sialon sintered body is a crystal particle of ceramics composed of Si (silicon), Al (aluminum), O (oxygen), and N (nitrogen). Sialon is formed by adding a sintering aid or the like to a raw material powder containing constituent elements such as Si, Al, O, and N such as silicon nitride, alumina, aluminum nitride, and silica, which are raw materials, and sintering the mixture. The sialon particles include _{β-sialon represented by the composition formula Si 6-Z} Al _{ZO Z} N _8-Z (0 <Z ≦ 4.2) and the composition formula Mx (Si, Al) ₁₂ (O, N). ₁₆ (0 <X ≦ 2, M indicates an element such as Mg, Ca, Sc, Y, Dy, Er, Yb, Lu, etc. that becomes an intrusive type and dissolves solidly) exists, such as α-sialon. doing. Like silicon nitride, β-sialon has a structure in which needle-like structures are entangled, so it has high toughness, and α-sialon has an equiaxed particle shape, so it has lower toughness than β-sialon. However, the hardness is high. In Sialon, the ratio of α-Sialon to β-Sialon is not particularly limited.

The sialon sintered body contains 1% by mass of rare earth elements used as a sintering aid, for example, at least one element selected from the group consisting of Sc, Y, Dy, Yb, Er, Ce and Lu in terms of oxide. It may contain ~ 7% by mass.

From the viewpoint of further improving the peel resistance of the diamond layer 5, the sialon sintered body preferably contains Al (aluminum) in an oxide equivalent of 2% by mass or more and 35% by mass or less, and 5% by mass or more and 30% by mass or less. It is more preferably contained below, and further preferably contained in an amount of 15% by mass or more and 25% by mass or less.

From the following viewpoints, the sialon sintered body preferably contains at least one selected from Ti (titanium) nitrides, carbonitrides, and carbides in a total amount of 5% by mass or more and 20% by mass or less. It is more preferable to contain 5% by mass or more and 15% by mass or less, and it is further preferable to contain 5% by mass or more and 10% by mass or less in total. Further peeling resistance can be expected when the Sialon sintered body contains the above compound of Ti (titanium) within the above range. That is, the tensile stress and the compressive stress are random by combining the Sialon sintered body of the matrix having a coefficient of thermal expansion smaller than that of the diamond layer 5 and the above compound of Ti (titanium) having a thermal expansion larger than that of the diamond layer 5. The thermal expansion of the entire sintered body is within the range of the above relational expression 1 while the stress is canceled out, and further peeling resistance can be expected.
Preferable examples of Ti (titanium) nitrides, carbonitrides, and carbides include TiC _x N _(1-x) (0 ≦ X ≦ 1).

The sialon sintered body preferably contains a polytype crystal phase from the viewpoint of further improving the peel resistance. The polytype is preferably at least one selected from the group consisting of 12H, 15R, and 21R. That is, the Sialon sintered body includes 12H-Sialon (general formula: SiAl ₅ O ₂ N ₅ ), 15R-Sialon (general formula: SiAl ₄ O ₂ N ₄ ), and 21R-Sialon (general formula: SiAl ₆ O _2). It preferably contains at least one polytype sialon selected from the group consisting of N _6).
Further peeling resistance can be expected because the Sialon sintered body contains a polytype crystal phase. That is, tensile stress and compressive stress are formed by combining a matrix sialon (α-sialon, β-sialon) having a coefficient of thermal expansion smaller than that of the diamond layer 5 and a polytype sialon having a thermal expansion larger than that of the diamond layer 5. Is randomly applied and the stress is canceled out, the thermal expansion of the entire sintered body is within the range of the above relational expression 1, and further peeling resistance can be expected.
The polytype crystal phase contained in the Sialon sintered body can be identified by X-ray diffraction analysis of the sintered body.

(3) Diamond layer 5
As schematically shown in FIG. 1, the diamond layer 5 has a plurality of voids 9 extending in the crystal growth direction from a portion in contact with the base material 3. Here, the "crystal growth direction" refers to the vector direction in which the distance from the base point to the surface of the diamond layer 5 is the shortest when a specific point on the surface 3A of the base material 3 is used as the base point. , Means the upward direction of FIG. Note that FIG. 1 conceptually shows an SEM image obtained by observing the cut surface of the diamond-coated cutting tool 1 with a SEM (Scanning Electron Microscope), and accurately shows an actual SEM image. It's not a thing. FIG. 1 is a conceptual diagram of an SEM image of a cut surface cut in a direction perpendicular to the surface 3A of the base material 3. When observing the void 9 by SEM, the diamond-coated cutting tool 1 including the diamond layer 5 is cut together with the base material 3, and a sample for SEM observation is prepared on the cut surface using a commercially available cross-section sample preparation device. .. Then, the void 9 can be observed by magnifying and observing the vicinity of the interface between the base material 3 and the diamond layer 5 of the sample by SEM.

The void 9 in the present disclosure has a width W of 100 nm or more and 500 nm or less in the direction perpendicular to the crystal growth direction (direction along the surface 3A of the base material 3, lateral direction in FIGS. 1 and 2) on the cut surface. It is defined that the length LP in the direction along the crystal growth direction (perpendicular to the surface 3A of the base material 3, vertical in FIGS. 1 and 2) is 100 nm or more and 1 μm or less. The width W is the length of the gap 9 along the vertical direction (horizontal direction in FIGS. 1 and 2) from the one end side to the other end side in the vertical direction (horizontal direction in FIGS. 1 and 2). be. The length LP is the length of the void 9 along the crystal growth direction (vertical direction in FIGS. 1 and 2) from the one end side to the other end side in the crystal growth direction (longitudinal direction in FIGS. 1 and 2). .. A case where the shape is different from the gap 9 shown in FIGS. 1 and 2 is illustrated in FIG. 3, and the width W and the length LP in the case of FIG. 3 are illustrated. The shapes of the voids 9 shown in FIGS. 1 to 3 do not always accurately indicate the actual shapes.
In the diamond-coated cutting tool 1 of the present disclosure, in the cut surface obtained by cutting the diamond-coated cutting tool 1 on the surface including the base material 3 and the diamond layer 5, the distance L between the centers 9A of the adjacent voids 9 is L. The average (average interval) is 12 μm or more and 1000 μm or less, preferably 12 μm or more and 500 μm or less, and more preferably 14 μm or more and 100 μm or less. The center 9A of the gap 9 is the center in the vertical direction (horizontal direction in FIGS. 1, 2 and 3). The interval L is the distance between the centers 9A of the adjacent voids 9 in the vertical direction.
The average interval is calculated as follows, for example. A plurality of (for example, 50) SEM images (for example, 5000 times) are continuously obtained from the position of the cutting edge of the diamond-coated cutting tool 1 in the direction away from the cutting edge. That is, by connecting a plurality of SEM images, the interface between the base material 3 and the diamond layer 5 can be observed. The field of view of each SEM image can be, for example, 18 μm × 24 μm, but in short, it is sufficient that the average interval can be specified by observing the interface of at least 1000 μm from the position of the cutting edge of the diamond-coated cutting tool 1. The obtained plurality of SEM images are analyzed by WinLoof (image analysis / measurement software Mitani Corporation), and the distance L between the centers 9A of the adjacent voids 9 is obtained. The obtained intervals L are averaged (arithmetic mean) to obtain an average interval.

The diamond layer 5 preferably has a multi-layer structure in order to reduce the surface roughness of the film and provide high film toughness. The diamond layer 5 is preferably made of polycrystalline diamond. Here, the polycrystalline diamond is a diamond in which fine particles are tightly bonded. The diamond layer 5 may contain heteroatoms such as boron, nitrogen, and silicon, and unavoidable impurities other than these elements.

The method for forming the diamond layer 5 is not particularly limited. As a method for forming the diamond layer 5, a CVD method (chemical vapor deposition) is preferable. Examples of the CVD method include a microwave plasma CVD method, a hot filament CVD method, and a high frequency plasma CVD method. Among these CVD methods, a microwave plasma CVD method in which a film having a fine crystal grain size and a small surface roughness can be easily obtained is preferably used.

The thickness of the diamond layer 5 is not particularly limited. The thickness of the diamond layer 5 is preferably 8 μm or more and 20 μm or less. At 8 μm or more, the adhesion is improved, and at 20 μm or less, the cutting edge is easily sharpened, so that the cutting performance is improved.

(4) Reason for presuming that the structure of the present disclosure enhances the adhesion of the diamond layer 5 to the base material 3 and improves the peeling resistance. The coefficient of thermal expansion of the diamond layer 5 (diamond coating) is 3.1 × ^10-6 /. It is K, and in order to reduce the residual stress, it is necessary to make the coefficients of thermal expansion of the diamond layer 5 and the base material 3 as close as possible. However, when the coefficient of thermal expansion of the base material 3 is smaller than that of the diamond layer 5, tensile stress is applied to the diamond layer 5, and the adhesion of the diamond layer 5 to the base material 3 is lowered. Therefore, the coefficient of thermal expansion of the base material 3 needs to be close to the coefficient of thermal expansion of the diamond layer 5 and large. By setting the average coefficient of thermal expansion x of the base material 3 to the specific range shown in the above relational expression 1, the coefficient of thermal expansion of the diamond layer 5 and the base material 3 are close to each other, and the tensile stress applied to the diamond layer 5 is suppressed. It is presumed that the adhesion of the diamond layer 5 to the base material 3 is improved.
Further, it is presumed that the diamond-coated cutting tool 1 of the present disclosure has improved peeling resistance for the following reasons. If the distance between the voids 9 at the interface of the base material 3 is narrow, the contact area between the diamond layer 5 and the base material 3 becomes small, and the adhesion of the diamond layer 5 to the base material 3 decreases. On the other hand, if the gaps 9 are too wide, residual stress is accumulated at the interface and the adhesion is lowered. In the diamond-coated cutting tool 1 of the present disclosure, by adjusting the average distance between the centers 9A of the adjacent voids 9 to 12 μm or more and 1000 μm or less, the starting point of peeling is reduced and the residual stress at the interface is also suppressed. Therefore, it is presumed that the peel resistance is improved.
It is presumed that the improved peeling resistance makes it difficult for peeling to occur not only at the initial stage of cutting but also when the cutting process is continued for a long time, and the life of the tool is extended. Further, since the diamond-coated cutting tool 1 of the present disclosure can be used under more severe conditions, it is possible to improve the cutting efficiency.

2. Manufacturing Method of Diamond-Coated Cutting Tool 1 The manufacturing method of the diamond-coated cutting tool 1 is not particularly limited. An example of the manufacturing method of the diamond-coated cutting tool 1 is shown below.

(1) Raw material For example, the following raw material powder is used as a raw material.
・ Main component α-Si ₃ N ₄ powder ・ Sintering aid Y ₂ O ₃ (yttrium oxide), Yb ₂ O ₃ (ytterbium oxide), La ₂ O ₃ (lantern oxide), CeO ₂ (cerium oxide (IV)) ), Er ₂ O ₃ (erbium oxide), Dy ₂ O ₃ (disprocium oxide), MgO (magnesium oxide), MgCO ₃ (magnesium carbonate), Al ₂ O ₃ (aluminum oxide), AlN (aluminum nitride), ZrO ₂ Select from (zirconium oxide), TiN (titanium nitride), TiC (titanium carbide)

(2) Preparation of Base Material 3 Raw material powder, an organic binder dissolved in a solvent, and a solvent are wet-mixed using a ball to obtain a slurry. The slurry is dried and press-molded into a desired (tool) shape to obtain a molded product. The molded product is subjected to a degreasing treatment in a heating device under a predetermined atmosphere, for example, at 400 ° C. to 800 ° C. for 60 minutes to 120 minutes. Further, the degreased molded product is placed in a container and heated in a predetermined atmosphere at, for example, 1700 ° C. to 1900 ° C. for 120 minutes to 360 minutes to obtain a sintered body. When the theoretical density of the sintered body is less than 99%, HIP treatment (hot isostatic pressing method: Hot Isostatic Pressing) for 120 minutes to 240 minutes at, for example, 1500 ° C. to 1700 ° C. under a predetermined atmosphere of 1000 atm. ) To make a dense body with a theoretical density of 99% or more. The sintered body or compact body thus produced corresponds to the base material 3.

(3) Coating pretreatment A coating pretreatment may be performed before coating the diamond layer 5. The coating pretreatment is performed in order to improve the adhesion of the diamond layer 5 to the base material 3. Specifically, roughening treatment of the surface 3A of the base material 3 and the like are exemplified. For the roughening treatment, for example, chemical corrosion such as electrolytic polishing, sandblasting with abrasive grains such as SiC, etc. are used.

(4) Coating of diamond layer 5 (formation of diamond layer 5)
For the coating of the diamond layer 5, for example, a microwave plasma CVD method can be used. For example, methane (CH ₄ ), hydrogen (H ₂ ), carbon monoxide (CO) and the like are supplied and coated as a raw material gas. For example, the coating process repeats the following two steps. The following nucleation step and crystal growth step are repeated until the set film thickness is reached, and the diamond layer 5 having a multilayer structure is coated on the surface 3A of the base material 3.
The average spacing between the centers 9A of the adjacent voids 9 of the diamond layer 5 can be controlled by adjusting the average coefficient of thermal expansion of the base material 3 from 25 ° C. to 600 ° C. The reason why it can be controlled in this way is not clear, but it is presumed as follows. The surface 3A of the base material 3 is heated during the coating treatment and cooled after the coating treatment. Since the average coefficient of thermal expansion of the diamond layer 5 and the average coefficient of thermal expansion of the base material 3 are different, tensile stress or compressive stress is applied to the diamond layer 5 formed on the base material 3 during cooling to create voids 9. It is thought that it will occur. Therefore, it is presumed that by adjusting the average coefficient of thermal expansion of the base material 3, the tensile stress or the compressive stress can be controlled, and the average distance between the centers 9A of the adjacent voids 9 can be controlled. It can also be controlled by adjusting the surface roughness of the base material 5 by the coating pretreatment. It is presumed that this is because the tensile stress or compressive stress applied to the diamond layer 5 is also controlled by the surface roughness.
(4.1) Nucleation step The flow rate of methane and hydrogen is adjusted so that the concentration of methane becomes a set value set within the range of 10% to 30%. At this time, the surface temperature of the base material 3 is a set temperature defined in the range of 700 ° C. to 900 ° C., and the gas pressure in the reactor is in the range of ^{2.5 × 10 2} Pa to 3.0 × 10 ^{3 Pa.} At the set pressure specified in the above, the state is continued for 0.1 to 2 hours.
(4.2) Crystal growth step The flow rate of methane and hydrogen is adjusted so that the concentration of methane becomes a set value defined within the range of 1% to 4%. In this case, at a set temperature which the surface temperature of the substrate 3 is defined in the range of 800 ° C. to 900 ° C., the gas pressure in the reactor is ^{1.0 × 10 3 Pa~7.0 × 10 3} Pa range Crystals are grown at the set pressure specified in the above.

Hereinafter, a more specific description will be given with reference to Examples.
Experimental Examples 1 to 10 are Examples, and Experimental Examples 11 to 18 are Comparative Examples.
In Table 1, when "*" is attached like "11 *", it indicates that it is a comparative example.

1. 1. Fabrication of diamond-coated cutting tool (1) Fabrication of base material α-Si ₃ N ₄ powder having an average particle size of 1.0 μm or less, and Y ₂ O ₃ (yttrium oxide) and Yb ₂ O as sintering aids. ₃ (yttrium oxide), La ₂ O ₃ (lantern oxide), CeO ₂ (cerium oxide (IV)), Er ₂ O ₃ (erbium oxide), Dy ₂ O ₃ (disprocium oxide), MgO (magnesium oxide), MgCO ₃ (magnesium carbonate), Al ₂ O ₃ (aluminum oxide), AlN (aluminum nitride), ZrO ₂ (zirconium oxide), TiN (titanium nitride), TiC (titanium carbide) are blended as shown in Table 1. Weighed into raw material powder.
The raw material powder, an organic binder micro wax dissolved in ethanol, and ethanol to give a slurry by wet mixing in a ball mill with Si ₃ N ₄ balls made of. The slurry was dried and press-molded into the shape of SPGN422 according to the ISO standard to obtain a molded product.
The molded product was degreased in a heating device at 400 ° C. to 800 ° C. for 60 minutes to 120 minutes under a nitrogen atmosphere of 1 atm. Further, the degreased compact was placed into _Si 3 _{N 4} manufactured in the vessel, under a nitrogen atmosphere, by heating over 1700 ° C. to 1900 ° C. for 120 minutes to 360 minutes to obtain a sintered body. When the theoretical density of the sintered body was less than 99%, HIP treatment was further performed at 1500 ° C. to 1700 ° C. for 120 minutes to 240 minutes in a nitrogen atmosphere of 1000 atm to obtain a dense body having a theoretical density of 99% or more. .. The sintered body or compact body thus produced was used as a base material.

(2) Coating A microwave plasma CVD method was used to coat the diamond layer. _{Methane (CH 4} ), hydrogen (H ₂ ), carbon monoxide (CO), etc. were used as the raw material gas. In the coating treatment, the nucleation step described in the column (4.1) and the crystal growth step described in the column (4.2) are repeated until the set film thickness (12 μm) is reached, and the diamond layer having a multi-layer structure is formed. Was coated on the surface of the substrate.

2. Measurement method of diamond-coated cutting tool, etc. (1) Calculation method of Al oxide content and Ti compound content Al oxide content and Ti compound content are the base materials. Fluorescent X-ray (X-ray Fluorescence Compound) was measured and calculated in.
Here, the Ti compound means at least one selected from Ti nitrides, carbonitrides, and carbides.

(2) Crystal phase identification method The polytype sialon contained in the sintered body was identified by X-ray diffraction analysis of the base material. Here, the polytype sialons are 12H-sialon (general formula: SiAl ₅ O ₂ N ₅ ), 15R-sialon (general formula: SiAl ₄ O ₂ N ₄ ), and 21R-sialon (general formula: SiAl ₆ O). It is at least one selected from the group consisting of ₂ N _6).

(3) Method for measuring the coefficient of thermal expansion Each base material was measured using TMA (Thermo Mechanical Analysis). The measurement conditions are R.M. The temperature was 10 ° C./min at T (25 ° C.) to 1000 ° C. under an Ar atmosphere.

(4) Method of observing voids Observation was performed with a scanning electron microscope (SEM). Specifically, a diamond-coated cutting tool was cut together with the base material including the diamond layer, and the interface between the diamond layer and the base material was polished by ion milling to prepare a sample for SEM observation. Then, the presence or absence of voids and the spacing between voids were measured by magnifying and observing the vicinity of the interface with SEM. At this time, 50 SEM images (5000 times) were continuously obtained from the position of the cutting edge of the diamond-coated cutting tool toward the direction away from the cutting edge. The field of view of each SEM image was 18 μm × 24 μm. The obtained 50 SEM images were analyzed by WinLoof (image analysis / measurement software Mitani Corporation), and the distance between the centers of adjacent voids was determined. Then, the obtained intervals were averaged to obtain an average interval.
The voids when measuring the average interval have a width of 100 nm or more and 500 nm or less in the direction perpendicular to the crystal growth direction and a length of 100 nm or more and 1 μm or less in the direction along the crystal growth direction on the cut surface. The voids of were used. In other words, voids that did not meet this requirement were not used to measure the spacing.

3. 3. Cutting test of diamond-coated cutting tool (1) Test method A cutting test was conducted using each diamond-coated cutting tool. The test conditions are as follows. In the cutting test, the number of passes from the diamond-coated cutting tool to the peeling of the diamond layer was measured. The higher the number of passes, the higher the evaluation. The evaluation was as follows.
<Test conditions>
-Work material: Aluminum material (AC4A-T6)
・ Cutting speed: 300m / min
・ Cut amount: 1.0 mm
-Feed amount: 0.25 mm / rev.
-Length per pass (1 pass): 200 mm
・ Cutting environment: With cooling water

<Evaluation>
"A" ... 1400 passes or more "B" ... 1000 passes or more and less than 1400 passes "C" ... 900 passes or more and less than 1000 passes "D" ... less than 900 passes

(2) Test results Table 1 shows the test results.
Average thermal expansion coefficient x is satisfies ^{3.1 × 10 -6 /K≦x≦4.0×10 -6 / K} , and the average distance between the centers of each of said voids adjacent is 12μm or more 1000μm or less All of Experimental Examples 1 to 10 had a good evaluation of "C" or higher. In contrast, the average thermal expansion coefficient x is not a ^{3.1 × 10 -6 /K≦x≦4.0×10 -6 / K} , or the average distance between the centers of each of said voids adjacent Experimental Examples 11 to 17 which were not 12 μm or more and 1000 μm or less were all evaluated as “D”, which was not good. More specifically, Experimental Examples 1 to 10 have at least 900 passes to peel off, whereas Experimental Examples 11 to 17 have at most 600 passes to peel off, which is tolerable. The peelability was significantly different.
Comparing Experimental Examples 1, 2 and 3, Experimental Example 3 containing Al in an oxide equivalent of 2% by mass or more and 35% by mass or less was evaluated higher than Experimental Examples 1 and 2 outside this range.
Comparing Experimental Examples 1, 2 and 4, Experimental Example 4 containing 5% by mass or more and 20% by mass or less of Ti nitride (TiN) was evaluated higher than Experimental Examples 1 and 2 outside this range.
Comparing Experimental Examples 3, 5, 6, 7, and 8, Experimental Examples 5, 6, 7, and 8 containing a polytype crystal phase were evaluated higher than Experimental Example 3 not containing a polytype crystal phase. ..

The present disclosure is not limited to the embodiments detailed above, and various modifications or changes can be made within the scope of the claims of the present disclosure.

1 ... Diamond-coated cutting tool 3 ... Base material 3A ... Surface 5 ... Diamond layer 9 ... Void 9A ... Center

Claims (5)

A diamond-coated cutting tool comprising a base material and a diamond layer covering the surface of the base material.
The base material has an average coefficient of thermal expansion x at 25 ° C to 600 ° C.
3.1 × ^{10 -6} /K≦x≦4.0×10 -6 / K
The diamond layer has a plurality of voids extending in the crystal growth direction from the portion in contact with the base material.
In a cut surface obtained by cutting the diamond-coated cutting tool on a surface including the base material and the diamond layer, the average distance between the centers of the adjacent voids is 12 μm or more and 1000 μm or less. tool. The diamond-coated cutting tool according to claim 1, wherein the base material is made of a silicon nitride sintered body or a sialon sintered body. The diamond-coated cutting tool according to claim 2, wherein the Sialon sintered body contains Al in an oxide equivalent of 2% by mass or more and 35% by mass or less. The silicon nitride sintered body contains at least one selected from Ti nitrides, carbonitrides, and carbides in a total amount of 5% by mass or more and 20% by mass or less.
The diamond-coated cutting according to claim 2 or 3, wherein the Sialon sintered body contains at least one selected from Ti nitrides, carbonitrides, and carbides in a total amount of 5% by mass or more and 20% by mass or less. tool. The diamond-coated cutting tool according to any one of claims 2 to 4, wherein the Sialon sintered body contains a polytype crystal phase.

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