JPH05177411A - Cover cutting tool and its manufacture - Google Patents

Abstract

PURPOSE:To provide a cover cutting tool excellent both in corrosion resistance and in chipping resistance and its manufacturing method. CONSTITUTION:This cover cutting tool is equipped with the first cover layer on the surface of a parent material, which consists of hard ceramics and in which minute cracks the average interval between which is 10-100mum and the average length in the layer thickness direction of which is from -2mum to +5mum of the layer thickness are made and in which tensile stress is remaining, and the second cover layer, which consists of hard ceramics provided on the first cover layer and in which compression stress is remaining. Furthermore, the first cover layer is made by chemical deposition method, and the cracks in the first cover layer are made by the blast treatment with GC grinding particles, etc., or barrel treatment, or quenching, and the second cover layer is made by a physical deposition method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated cutting tool having a hard ceramic coating layer on a base material of cemented carbide, cermet or hard ceramic, and a method for producing the same.

[0002]

2. Description of the Related Art A cutting tool made of hard alloy such as cemented carbide or cermet or hard ceramics such as silicon nitride, alumina or titanium compound is used for cutting general steel and castings. However, it is known that the cutting edge temperature of the cutting tool during cutting becomes 800 ° C. or higher, and if the cutting edge temperature rises, the cutting tool is deformed by heat and the flank wear becomes severe.

In order to improve the cutting characteristics of the cutting tool under such circumstances, a coating layer composed of a single layer or a composite layer of hard ceramics is formed on the surface of the tool base material made of cemented carbide, cermet or hard ceramics. The formed coated cutting tool is used. The hard ceramics constituting the coating layer are TiC, TiN, TiCN, etc.
Carbides, nitrides, carbonitrides, Al ₂ O _{3 and the} like of Group A metals are generally used. Further, in forming these coating layers, a chemical vapor deposition method such as a CVD method or a physical vapor deposition method such as an ion sputtering method is used.

Generally, the coating layer formed by the chemical vapor deposition method has a very high adhesion strength with the base material because it is diffused between the coating material and the base material. The abrasion resistance is much better than the ones. On the other hand, however, this type of coated cutting tool has a drawback that the cutting edge strength is lower and the fracture resistance is lower than that of a cutting tool only made of cemented carbide, cermet or hard ceramics. The reason is that if a crack starts from the surface of the coating layer during cutting, the propagation of the crack is promoted by the tensile stress generated in the coating layer due to the difference in the coefficient of thermal expansion between the base material and the coating layer, and it spreads and becomes defective. It is thought that it will be reached.

That is, the coefficient of thermal expansion of the base material is about 5.5 × 10 ^-6 K ^{-1 for} cemented carbide, and Si ₃ for hard ceramics.
It is about 3.0 × 10 ⁻⁶ K ^{−1 in} N ₄ system, but in the coating layer, for example, TiC is about 7.6 × 10 ⁻⁶ K ⁻¹ and Al ₂ O ₃ is about 7.9 × 10 ^{−. It is 6} K ^-1 . In the chemical vapor deposition method, the coating temperature is as high as about 1000 ° C. Therefore, if the coating layer is cooled to room temperature after formation, tensile stress acts on the coating layer due to the difference in the thermal expansion coefficient, which promotes the propagation of cracks. is there. The coating layer thickness of the coated cutting tool currently generally used is in the range of about several μm to about ten and several μm, although the wear resistance is improved as the coating layer thickness is increased, but at the same time, For the above reason, the thicker the coating layer is, the lower the fracture resistance is.

Therefore, if it is possible to improve the fracture resistance of the coating layer formed by the chemical vapor deposition method, it is possible to provide the cutting characteristics which are more excellent than the conventional ones in combination with the original excellent wear resistance. It is possible to obtain a coated cutting tool, and it is possible to improve and improve the tool life even in cutting operations that are subject to intermittent loads such as milling and turning of grooved materials, which conventionally had very many cutting edges. Become.

However, up to now, as a method for preventing the deterioration of the cutting edge strength of the coated cutting tool and improving the fracture resistance, a method of making the coating layer of the cutting edge portion thinner than a flat portion, and a tensile stress remaining in the coating layer Method by releasing shot peening or shot blasting (Japanese Patent Laid-Open No. 3-922)
No. 04 and Japanese Patent Application Laid-Open No. 3-92205) have been tried, but the present situation is that the sufficient effect has not yet been obtained.

[0008]

In view of such conventional circumstances, the present invention maintains good wear resistance derived from excellent adhesion strength of a coating layer by a chemical vapor deposition method to a base material,
It is an object of the present invention to provide a coated cutting tool excellent in both wear resistance and fracture resistance by improving and improving the fracture resistance, which has been conventionally unfavorable, and to provide a manufacturing method thereof.

[0009]

In order to achieve the above object, a hard ceramics, a cermet, or a base metal surface of a silicon nitride-based, alumina-based or titanium compound-based hard ceramics of the present invention is formed on the surface of the hard ceramics. In the coated cutting tool provided with the coating layer, the coating layer is provided on the surface of the base material, and the average crack interval is 10 to 100 μm, and the average crack length in the layer thickness direction is from layer thickness −2 μm to layer thickness +5.
At least one selected from carbides, nitrides, carbonitrides, carbonates, carbonitrides, boronitrides, borocarbonitrides, and aluminas of Group 4A metals of the periodic table having microscopic cracks of μm. A first coating layer consisting of a single layer or multiple layers of seeds, in which tensile stress remains, and a carbide, nitride, carbonitride, carbonitride of Group 4A metal of the periodic table provided thereon , And at least one kind of single layer or multiple layers selected from alumina, titanium aluminum nitride, and titanium aluminum oxynitride, and a second coating layer in which compressive stress remains.

Further, the method of manufacturing the coated cutting tool of the present invention comprises:
Carbide, nitride, carbonitride, carbonic acid of Group 4A metal of the periodic table is formed on the surface of the base material made of cemented carbide, cermet, or silicon nitride-based, alumina-based or titanium compound-based hard ceramics by the chemical vapor deposition method. Oxide, carbonitride, boronitride, borocarbonitride, and alumina are coated in a single layer or multiple layers, and then iron powder or alumina powder or ceramic grains such as GC abrasive grains are used. The average crack distance is 10 to 10 by blasting or barreling, or by applying thermal shock by burning.
The average of 100 μm and the crack length in the layer thickness direction is the layer thickness −2 μ.
A microcrack having a layer thickness of +5 μm from m is generated, and 4 of the periodic table is formed on the obtained first coating layer by physical vapor deposition.
A second coating layer composed of a single layer or multiple layers selected from the group consisting of carbides, nitrides, carbonitrides, carbonates, carbonitrides of Group A metals, alumina, titanium aluminum nitride and titanium aluminum oxynitride. Is formed.

[0011]

When a coating layer of hard ceramics is formed on the surface of a base material made of cemented carbide, cermet or hard ceramics by a known chemical vapor deposition method such as the CVD method, tensile stress may occur in the coating layer as described above. Are known. At that time, when the layer thickness of the coating layer is from several μm to several tens of μm, the generated tensile stress exceeds the breaking strength of the coating layer, and thus fine cracks naturally occur at an average interval of 100 to 400 μm. Then, a part of the tensile stress is released. But,
Nevertheless, it can be confirmed by X-ray diffraction measurement that elastic strain of about 0.5 to 1.0 GPa remains in the coating layer, which promotes the propagation of cracks during cutting.

Therefore, in the present invention, iron powder, alumina powder or GC abrasive grains (SiC abrasive grains exhibiting a green color of high purity) are blasted on the coating layer, or the coating layer is rotated in a container together with the abrasive grains. Alternatively, by a barrel treatment that gives vibration or by applying a thermal shock due to quenching, forcibly generating fine cracks and further releasing the tensile stress, the coating layer with the reduced tensile stress remains. By providing a second coating layer on which a compressive stress remains by a physical vapor deposition method as the first coating layer, excellent adhesiveness with the base material and excellent wear resistance are maintained, and at the same time excellent It was possible to obtain a coated cutting tool that also had fracture resistance.

The average gap between the cracks of the first coating layer is 100 μm.
m or less and the average crack length in the layer thickness direction is -2 μm
It has been found that the tensile stress of about 0.4 to 0.5 GPa can be further released when the average crack length is exceeded, but when the average spacing between the cracks is less than 10 μm, the wear resistance decreases and the average crack length increases. When the layer thickness exceeds +5 μm (cracks extend into the base material), the fracture resistance decreases, so the cracks in the first coating layer have an average interval of 10 to 100 μm and an average length in the layer thickness direction- It is necessary to make the range from 2 μm to the layer thickness + 5 μm.
The lengths and intervals of the cracks are measured by observing with an optical microscope after cutting the tool to mirror-finish the cross section of the coating layer, and obtaining an average value from the observation of a plurality of cross sections. or,
The value of the residual stress can be measured by X-ray diffraction as described above.

First forcibly introducing cracks as described above
Even in the coating layer, tensile stress still remains because the distribution and length of cracks are limited. Therefore, even if the strength of the cutting edge is improved only with the first coating layer, sufficient fracture resistance cannot be obtained yet. Therefore, by utilizing the fact that the compressive stress remains in the coating layer formed by a known physical vapor deposition method such as the ion sputtering method, a physical vapor deposition method is performed on the first coating layer in which the tensile stress remains. As a result of forming the two coating layers, it was confirmed that a compressive stress of about 0.9 to 2.0 GPa remained, whereby the fracture resistance in cutting could be greatly improved.

Regarding the layer thicknesses of the first coating layer and the second coating layer, the layer thickness of the first coating layer is set in the range of 2 to 15 μm, and the layer thickness of the second coating layer is set in the range of 1 to 5 μm. Is preferred. Outside this range, it becomes difficult to maintain an appropriate balance between the tensile stress and the compressive stress remaining in each coating layer, and if the first and second coating layers are too thick, the fracture resistance is improved. As a result, the wear resistance or fracture resistance of the coated cutting tool is reduced in any case.

[0016]

Example 1 A base material made of a cemented carbide of ISO P30 having a cutting tool shape of model number SDKN42MT was prepared,
The surface thereof was coated with TiCN having a layer thickness of 2 μm and Al ₂ O ₃ having a layer thickness of 2 μm in this order by a known CVD method, and was naturally returned by returning to room temperature or forcedly by a blast treatment using GC abrasive grains. Cracks having an average interval and an average length shown in Table 1 below were generated to form a first coating layer in which tensile stress was partly released. Then, for the samples of the examples of the present invention, the second coating layer shown in Table 1 was formed on the first coating layer by a known ion plating method. The intervals and lengths of the cracks are average values obtained by measuring a plurality of cross sections by measuring the cross section of the coating layer after mirror finishing and observing with an optical microscope.

The cutting performance of each of the obtained coated cutting tools was evaluated under the following cutting conditions, and the results are also shown in Table 1. Wear resistance Work material: SCM435 Cutting speed: 270 m / min. Feed: 0.37 mm / blade Cutting: 2.0 mm Cutting time: 30 min. Fracture resistance Work material: SCM435 grooved material (4 grooves in the longitudinal direction at equal intervals on the outer circumference) Cutting speed: 300 m / min. Feed: 0.41 mm / blade Cutting depth: 2.0 mm Cutting time: 8 passes

[0018]

[Table 1] Sample crack average crack average crack average second coating layer flank wear defect rate No formation method interval (μm) length (μm) (layer thickness μm) wear amount (mm) (%) 1 none 400 Layer thickness ± 0 None 0.20 100 2 GC blast 100 Layer thickness ± 0 None 0.21 90 3 * GC blast 100 Layer thickness ± 0 TiN (2) 0.195 40 (Note) Samples 1 and 2 are comparative examples, sample 3 is this It is an example of the invention.

Sample 1 in which the first coating layer was still formed by the CVD method and cracks were forcibly formed in the first coating layer (the average interval and the average length are within the scope of the present invention), but the second coating was used. It can be seen that, in comparison with the sample 2 having no layer, the sample 3 of the present invention maintains excellent flank wear resistance, and at the same time, the fracture resistance is greatly improved.

[0020]

Example 2 A base material made of a cemented carbide of ISO P10 having a cutting tool shape of model number CNMG432 was prepared, a surface of the base material was coated with a hard ceramic by a known CVD method, and then naturally returned to room temperature. Alternatively, a blasting treatment, a barreling treatment, or a burning treatment was used to forcibly generate cracks to form the first coating layer in which the tensile stress shown in Table 2 below was partially released. Then, the second coating layer shown in Table 2 was formed on the first coating layer except for the samples 4 and 5 by a known ion plating method. The intervals and lengths of the cracks are average values obtained by measuring a plurality of cross sections by measuring the cross section of the coating layer after mirror finishing and observing with an optical microscope.

[0021]

[Table 2] Sample 1st coating layer Crack spacing of cracks Crack average 2nd coating layer No (layer thickness μm) Forming method average (μm) Length (μm) (layer thickness μm) 4 TiCN (10) / Al ₂ O ₃ (5) None 400 Layer thickness ± 0 None 5 TiCN (10) / Al ₂ O ₃ (5) GC Blast 100 Layer thickness ± 0 None 6 TiCN (10) / Al ₂ O ₃ (5) Al ₂ O ₃ blast 8 layer thickness +5 TiCN (2) / TiC (3) 7 TiCN (10) / Al ₂ O ₃ (5) GC blast 110 layer thickness −2 TiN (2) / TiCN (3) 8 TiCN (10) / Al ₂ O ₃ (5) Tempered 80 layer thickness +6 TiCN (2) / TiC (3) 9 TiCN (10) / Al ₂ O ₃ (5) Al ₂ O ₃ blast 50 Layer thickness -3 TiCN (2 ) / TiC (3) 10 TiCN (1.0) GC blast 50 Layer thickness ± 0 TiCN (2) / TiC (3) 11 TiC (14) / Al ₂ O ₃ (2) GC blast 50 Layer thickness ± 0 TiCN (2 ) / TiC (3) 12 * TiC (10) / Al ₂ O ₃ (5) GC Blast 100 Layer thickness ± 0 TiCN (2) / TiC (3) 13 * TiCN (10) / Al ₂ O ₃ (5) GC barrel 100 Layer thickness −2 TiCN (2) / TiC (3) 14 * TiCN (1) / Al ₂ O ₃ (1) Fe Blast 10 layer thickness +5 TiCN (2) / TiC (3) 15 * TiCN (1 ) / Al ₂ O ₃ (1) Baked 100 layer thickness + 5 TiCN (2) / TiC (3) 16 TiCN (10) / Al ₂ O ₃ (5) Al ₂ O ₃ blast 100 Layer thickness ± 0 TiAlN (0.5) 17 * TiCN (10) / Al ₂ O ₃ (5 ) Al ₂ O ₃ blast 100 layer thickness ± 0 TiAlN (1) 18 TiCN (10) / Al ₂ O ₃ (5) Al ₂ O ₃ blast 100 layer thickness ± 0 TiAlN (6) (Note) 11, 16 and 18 are comparative examples,
12 to 15 and 17 are examples of the present invention.

Using each of the obtained coated cutting tools, the cutting performance was evaluated under the following cutting conditions, and the results are shown in Table 3. Wear resistance Work material: SCM415 Cutting speed: 250 m / min. Sending: 0.3 mm / rev. Depth of cut: 1.5 mm Cutting time: 20 min. Fracture resistance Work material: SCM435 grooved material (4 grooves in the longitudinal direction at equal intervals on the outer circumference) Cutting speed: 100 m / min. Sending: 0.15-0.25 mm / rev. Depth of cut: 2.0 mm Cutting time: 0.5 min.

[0023]

[Table 3] (Note) 4 to 11, 16 and 18 in the sample are comparative examples,
12 to 15 and 17 are examples of the present invention.

Samples 4 and 5 have the same structure as the conventional one in which only the first coating layer in which the tensile stress is partly released and the second coating layer is not formed thereon are used. It can be seen that Samples 12 to 15 and 17 of the present invention have excellent flank wear resistance, and at the same time, have significantly improved fracture resistance. Further, the samples 6 to 9 of the comparative example have the second coating layer on the first coating layer in which the tensile stress is partially released, but the average spacing or the average length of the cracks of the first coating layer is within the range of the present invention. Sample 1 of the present invention in the fracture resistance because it is outside
It is inferior to 2-15 and 17. Comparing Samples 10 and 11 with Sample 12, since Sample 10 and 11 have a layer thickness of the first coating layer outside the scope of the present invention, Sample 10 has wear resistance and Sample 11 has fracture resistance, and Sample 12 has Inferior. Comparing Samples 16 and 18 with Sample 17, both Samples 16 and 18 are inferior in fracture resistance to Sample 17 because the thickness of the second coating layer is outside the range of the present invention. From these results, it is understood that the thickness of the first coating layer is preferably in the range of 2 to 15 μm and the thickness of the second coating layer is in the range of 1 to 5 μm.

[0025]

According to the present invention, as the coating layer of the cutting tool base material, a first coating layer formed by a chemical vapor deposition method and having a moderate release of tensile stress by the introduction of cracks, and a first coating layer Since the second coating layer formed by the physical vapor deposition method and having residual compressive stress is laminated thereon, excellent adhesion strength to the base material and good balance of residual stress in the entire coating layer can be obtained. Therefore, it is possible to provide a coated cutting tool having excellent wear resistance and greatly improved fracture resistance.

Therefore, according to the coated cutting tool of the present invention,
Conventionally, even in a cutting process in which an intermittent load is applied, such as a milling process in which the cutting edge has many defects, a turning process of a grooved material, etc., a much longer tool life can be obtained by improving the fracture resistance.

Claims (4)

[Claims] 1. A coated cutting tool in which a hard ceramic coating layer is provided on the surface of a base material made of cemented carbide, cermet, or silicon nitride-based, alumina-based, or titanium compound-based hard ceramics. Provided on the surface of the base material, the average of the crack intervals is 10 to 100 μm, and the average of the crack lengths in the layer thickness direction is from the layer thickness −2 μm to the layer thickness +5.
At least one selected from carbides, nitrides, carbonitrides, carbonates, carbonitrides, boronitrides, borocarbonitrides, and aluminas of Group 4A metals of the periodic table having microscopic cracks of μm. A first coating layer consisting of a single layer or multiple layers of seeds, in which tensile stress remains, and a carbide, nitride, carbonitride, carbonitride of Group 4A metal of the periodic table provided thereon And a second coating layer comprising at least one single layer or multiple layers selected from alumina, titanium aluminum nitride, and titanium aluminum oxynitride, and a second coating layer in which compressive stress remains. 2. The coated cutting tool according to claim 1, wherein the first coating layer has a layer thickness of 2 to 15 μm, and the second coating layer has a layer thickness of 1 to 5 μm. 3. A carbide, a nitride of a Group 4A metal of the periodic table on a surface of a base material made of a cemented carbide, a cermet, or a silicon nitride-based, alumina-based or titanium compound-based hard ceramics by a chemical vapor deposition method. Carbonitride, carbonate,
A single layer or multiple layers of at least one selected from carbonitride, boronitride, borocarbonitride, and alumina, and then blasting using iron powder, alumina powder, or ceramic particles such as GC abrasive particles. By treatment or barrel treatment,
Alternatively, by applying a thermal shock due to quenching, fine cracks having an average crack interval of 10 to 100 μm and an average crack length in the layer thickness direction from the layer thickness −2 μm to the layer thickness +5 μm are generated and obtained. On the first coating layer, a carbide, a nitride, a carbonitride of a Group 4A metal of the periodic table is formed by a physical vapor deposition method,
Manufacture of a coated cutting tool characterized by forming a second coating layer composed of a single layer or multiple layers of at least one selected from carbonates, carbonitrides, alumina, titanium aluminum nitride and titanium aluminum oxynitride. Method. 4. The layer thickness of the first coating layer is 2 to 15 μm,
The method for producing a coated cutting tool according to claim 3, wherein the layer thickness of the second coating layer is 1 to 5 µm.