JP2011031319A - Surface coated cutting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface-coated cutting tool that exhibits excellent chipping resistance and wear resistance with a hard coating layer in high-speed milling cutting of steel, cast iron and the like.
SOLUTION: From the surface of the tool substrate, (a) a lower layer made of a TiN layer, (b) a TiC layer having a fine grain vertically grown crystal structure, and a TiC layer, a TiN layer or a TiCN layer having a granular crystal structure. An intermediate layer composed of an alternating laminated structure with a Ti compound layer, and (c) an aluminum oxide layer, which is vapor-deposited as a hard coating layer, or an adhesive layer made of either a TiCO layer or a TiCNO layer, if necessary. A surface-coated cutting tool formed between the (b) intermediate layer and the (c) aluminum oxide layer.
[Selection figure] None

Description

  The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits excellent chipping resistance and wear resistance with a hard coating layer in high-speed milling that is accompanied by high heat generation and receives a large thermal shock. is there.

Conventionally, generally on the surface of a substrate (hereinafter collectively referred to as a tool substrate) composed of a tungsten carbide (hereinafter referred to as WC) -based cemented carbide or titanium carbonitride (hereinafter referred to as TiCN) -based cermet. A coated tool in which a hard coating layer composed of a Ti compound layer is formed by vapor deposition is known.
For example, it is known that a coated tool in which a hard coating layer is configured by alternately laminating TiC layers and TiN layers each having a granular crystal structure exhibits excellent fracture resistance and wear resistance (Patent Document 1). ).
In order to further improve the fracture resistance of the coated tool,
(A) The lower layer is a TiN layer having a granular crystal structure,
(B) an 1-TiCN layer having a vertically grown crystallographic structure in which the intermediate layer is divided vertically by a single TiN divided layer having a granular crystal structure,
(C) The upper layer is an Al ₂ O ₃ layer,
It is also known that a coated tool (hereinafter referred to as a conventional coated tool) in which a hard coating layer made of the above is formed on the surface of a tool substrate exhibits excellent interlayer adhesion and fracture resistance (Patent Document 2).
Here, for the purpose of improving the strength of the TiCN layer, the l-TiCN layer having the vertically grown crystal structure uses, for example, a mixed gas containing an organic carbonitride as a reaction gas in a normal chemical vapor deposition apparatus, It is also known that it is a TiCN layer having a vertically grown crystal structure formed by chemical vapor deposition in a medium temperature range of 700 to 950 ° C. (Patent Document 3).

JP 58-153770 A Japanese Patent Laid-Open No. 8-1408 Japanese Patent Laid-Open No. 6-8010

  In recent years, there has been a strong demand for energy saving and energy saving in cutting, and along with this, cutting tends to be performed under severer conditions, but the above-mentioned conventional coated tool is used under normal conditions such as steel and cast iron. When used for cutting, there is no particular problem. Especially when this is used for high-speed milling of steel or cast iron that is accompanied by high heat generation and large thermal shock, Chipping (small chipping) and defects are likely to occur, and as a result, the service life is reached in a relatively short time.

  In view of the above, the inventors of the present invention have excellent chipping resistance and chipping resistance in order to extend the life of the coated tool, and exhibit excellent wear resistance over a long period of use. As a result of intensive studies on the layer structure of the hard coating layer, the following knowledge was obtained.

(A) Since the l-TiCN layer divided by the TiN divided layer of the granular crystal structure constituting the intermediate layer of the hard coating layer in the conventional coating tool has excellent strength, it suppresses the generation of cracks in the hard coating layer. However, once a crack is generated, this crack tends to propagate and propagate particularly along the grain boundary of the l-TiCN grains in the layer, and this often causes chipping and defects.

(B) Therefore, the present inventors have made various studies on the layer structure of the intermediate layer. As a result, instead of the l-TiCN layer constituting one of the intermediate layers of the conventional coated tool, fine vertically grown crystals A Ti carbide layer having a structure (hereinafter referred to as a fine l-TiC layer) is formed, and an intermediate layer is formed as a fine l-TiC layer (Ti carbide layer having a fine grain growth crystal structure) and Ti carbide (TiC). When it is configured as an alternate layered structure with a granular Ti compound layer composed of one layer or two or more of a layer, a nitride (TiN) layer, and a carbonitride (TiCN) layer, a large thermal shock is generated with high heat generation. In the high-speed milling process, the number of thermal cracks increases as compared with the l-TiCN layer of the conventional coated tool, but on the other hand, the stress at which one crack is released is reduced and the crack is reduced. Progress-order propagation speed decreases, and as a result, chipping resistance, it was found that the chipping resistance is improved.

(C) The fine particle 1-TiC layer is, for example, 0.1 to 0 of a polishing liquid in which 25 to 35% by mass of Al ₂ O ₃ fine particles are blended as a spraying abrasive in a proportion of the total amount with water. Smoothing the surface of the lower layer by spraying with a spray pressure of 15 MPa and applying wet blasting,
Reaction gas composition: by _{volume%, TiCl 4: 1~3%,} CH 4: 0.5~1.5%, H 2: remainder,
Reaction atmosphere temperature: 900-950 ° C.
Reaction atmosphere pressure: 200 to 300 Torr (26 to 40 kPa),
It can form by vapor-depositing on condition of this.
This fine l-TiC layer has a fine grain structure with an average crystal grain size of 0.01 to 0.3 μm and a vertically long crystal structure. According to the fracture surface structure and the optical microscope structure observation, it is excellent. It has substantially the same longitudinally grown crystal structure as the 1-TiCN layer known as a Ti compound having high strength (Patent Document 2), and is far superior to the conventionally known granular crystal structure TiC layer. Furthermore, it has excellent toughness and also has excellent adhesion strength with the granular Ti compound layers constituting the alternate laminated structure, and improves interlayer adhesion strength.

(D) In the present invention, an Al ₂ O ₃ layer having excellent wear resistance is formed as an upper layer on the intermediate layer composed of the above-mentioned alternate laminated structure. When an adhesion layer consisting of one of a Ti carbon oxide (TiCO) layer and a carbonitride oxide (TiCNO) layer is interposed therebetween, the interlayer adhesion between the intermediate layer and the upper layer is further improved. I found out.

(E) Therefore, as a hard coating layer, on a lower layer composed of a granular Ti compound layer, a granular 1-TiC layer and granular Ti composed of one or more of a TiC layer, a TiN layer and a TiCN layer In the coated tool of the present invention, in which an intermediate layer composed of an alternately laminated structure with a compound layer is formed, an adhesion layer is formed if necessary, and an Al ₂ O ₃ layer is deposited as an upper layer, the intermediate layer is cracked. Because it has the effect of suppressing the progress and propagation speed of steel, it exhibits excellent chipping resistance and fracture resistance even when subjected to high-speed milling cutting of steel or cast iron that is accompanied by high heat generation and undergoes a large thermal shock. Since excellent wear resistance can be exhibited over use, the life of the coated tool can be extended.

This invention has been made based on the above findings,
“(1) On the surface of a tool base made of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet,
(A) a lower layer composed of a nitride layer of Ti having an average layer thickness of 0.1 to 2 μm,
(B) a carbide layer of Ti having a fine grain vertically grown crystal structure and having an average layer thickness of 0.5 to 3 μm;
A Ti compound layer having a granular crystal structure composed of one or more of a Ti carbide layer, a nitride layer, and a carbonitride layer, and having an average layer thickness of 0.2 to 1 μm;
An intermediate layer having a total average layer thickness of 3 to 10 μm, comprising an alternating laminated structure with
(C) an aluminum oxide layer having an average layer thickness of 0.5 to 5 μm,
A surface-coated cutting tool, wherein the hard coating layer constituted by the above (a) to (c) is formed with a total average layer thickness of 4 to 15 μm.
(2) Between the intermediate layer of the above (b) and the aluminum oxide layer of the above (c), it is composed of one layer of a Ti carbonate layer and a carbonitride oxide layer, and has a thickness of 0.1 to 1 μm. The surface-coated tool according to (1), wherein an adhesion layer having an average layer thickness is interposed. "
It has the characteristics.

  The present invention will be described in detail below.

Lower layer:
The lower layer composed of a Ti nitride (TiN) layer can be formed under normal chemical vapor deposition conditions, and as such has a high temperature strength so that the hard coating layer has a high temperature strength due to its presence. In addition, it firmly adheres to both the tool substrate and the intermediate layer, and thus has an effect of improving the adhesion of the hard coating layer to the tool substrate. However, when the average layer thickness is less than 0.1 μm, the above effect is achieved. On the other hand, if the average layer thickness exceeds 2 μm, chipping is likely to occur particularly in high-speed milling, so the average layer thickness was determined to be 0.1 to 2 μm.

Intermediate fine l-TiC layer:
The fine l-TiC layer constituting the alternate lamination of the intermediate layer is, for example, a polishing liquid containing 25 to 35 mass% Al ₂ O ₃ fine particles as a spraying abrasive in a proportion of the total amount with water. Smoothing the surface of the layer on which the fine l-TiC layer is deposited by spraying at a spray pressure of 0.1 to 0.15 MPa and applying wet blasting;
Reaction gas composition: by _{volume%, TiCl 4: 1~3%,} CH 4: 0.5~1.5%, H 2: remainder,
Reaction atmosphere temperature: 900-950 ° C.
Reaction atmosphere pressure: 200 to 300 Torr (26 to 40 kPa),
It can form by vapor-depositing on condition of this.
The fine-grained l-TiC layer itself has excellent toughness, and by alternately laminating with the granular Ti compound layer, it suppresses the coarsening of the granular crystal structure and delays the propagation and propagation speed of cracks, thereby preventing chipping resistance and resistance. Improve deficiency and increase the adhesion strength of alternating layers.
When the average layer thickness of the fine l-TiC layer is less than 0.5 μm, the fine growth of crystal grains in the granular Ti compound layer cannot be promoted and the effect of suppressing the coarsening of the crystal grains cannot be expected, When the average layer thickness exceeds 3 μm, the chipping resistance and chipping resistance tend to decrease. Therefore, the average layer thickness of the fine-grained l-TiC layer is set to 0.5 to 3 μm.

Granular Ti compound layer of the intermediate layer:
Further, the granular Ti compound layer constituting the alternate lamination of the intermediate layer is composed of a Ti compound layer having a granular crystal structure of one or more of a Ti carbide layer, a nitride layer, and a carbonitride layer. The chemical vapor deposition conditions can be used.
The granular Ti compound layer constituting the alternate lamination of the intermediate layer has high-temperature strength and firmly adheres to both the fine l-TiC layer constituting the alternate lamination and the Al ₂ O ₃ layer constituting the upper layer, The interlaminar adhesion strength is improved, but if the average layer thickness is less than 0.2 μm, the above-mentioned effect cannot be sufficiently exerted. On the other hand, if the average layer thickness exceeds 1 μm, the grains become coarse. Therefore, the average layer thickness was set to 0.2 to 1 μm.

Intermediate layer thickness:
If the total average layer thickness of the intermediate layer is less than 3 μm, sufficient wear resistance cannot be obtained. On the other hand, if the average layer thickness exceeds 10 μm, the chipping resistance and chipping resistance obtained by constituting the alternate lamination are reduced. Since a decreasing tendency is observed, the total average layer thickness of the intermediate layer is determined to be 3 to 10 μm.

Adhesion layer:
In the present invention, an adhesion layer composed of one of a Ti carbon oxide (TiCO) layer and a carbonitride oxide (TiCNO) layer is formed between the intermediate layer and the upper layer as necessary. be able to.
When the adhesion layer is formed between the intermediate layer and the upper layer within the range of the average layer thickness of 0.1 to 1 μm, the interlayer adhesion strength between the intermediate layer and the upper layer is further improved, and at the time of cutting It is possible to suppress the occurrence of abnormal damage such as chipping, chipping and peeling due to an impact load.

Upper Al ₂ O ₃ layer:
The upper Al ₂ O ₃ layer basically has the effect of maintaining the wear resistance of the hard coating layer. However, if the average layer thickness is less than 0.5 μm, the wear resistance over a long period of use. On the other hand, if the average layer thickness exceeds 5 μm, the high-temperature hardness and high-temperature strength due to the coarsening of the Al ₂ O ₃ crystal grains tend to decrease, and chipping resistance during high-speed milling cutting The average layer thickness was determined to be 0.5 to 5 μm because the property and wear resistance were lowered.

  A TiN layer having a golden color tone may be vapor-deposited on the surface of the upper layer as necessary for the purpose of identifying the cutting tool before and after use, but the average layer thickness in this case is 0.1 to 1 μm. It's okay. This is because if the thickness is less than 0.1 μm, a sufficient discrimination effect cannot be obtained, while the discrimination effect by the TiN layer is sufficient with an average layer thickness of up to 1 μm.

The coated tool of the present invention has a lower layer composed of a TiN layer, a fine l-TiC layer, and an intermediate layer composed of an alternately laminated structure of granular Ti compound (TiC, TiN, TiCN) layers as a hard coating layer on the tool base surface. If necessary, an adhesion layer composed of a TiCO layer, a TiCNO layer, and an upper layer composed of an Al ₂ O ₃ layer are formed by vapor deposition. In particular, an intermediate layer composed of alternating layers increases thermal cracks and opens cracks. In addition to reducing the stress caused by cracking and slowing the propagation and propagation of cracks, abnormal damage such as chipping, chipping, and delamination can occur when used in high-speed milling of steel and cast iron that are subjected to high heat generation and are subject to large impacts. Without being generated, excellent wear resistance is exhibited over a long period of use, and the life of the coated tool is extended.

Next, the coated tool of the present invention will be specifically described with reference to examples.
Here, a surface-coated cutting tool made of tungsten carbide-based cemented carbide will be described, but the present invention is not limited to this, and the same applies to a surface-coated cutting tool made of titanium carbonitride-based cermet. The

WC powder, TiC powder, ZrC powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder, TaN powder, and Co powder all having an average particle diameter of 1 to 3 μm are prepared as raw material powders. These raw material powders were blended into the composition shown in Table 1, added with wax, ball milled in acetone for 24 hours, dried under reduced pressure, and pressed into a green compact with a predetermined shape at a pressure of 98 MPa. The green compact was vacuum sintered at a predetermined temperature in the range of 1370 to 1470 ° C. for 1 hour in a vacuum of 5 Pa. After sintering, the cutting edge portion had a width of 0.15 mm and an angle of 20 Tool base made of WC-base cemented carbide with the throwaway tip shape specified in ISO · SEEN1203AFSN1 by machining R: 0.03mm to the Chamfor Honing A to F were produced.

Next, a normal chemical vapor deposition apparatus is used on the surfaces of these tool bases A to F,
(A) As a lower layer of the hard coating layer, a TiN layer is formed by vapor deposition under the conditions shown in Table 2 and the target layer thickness shown in Table 4.
(B) Next, a polishing liquid containing 25 to 35% by mass of Al ₂ O ₃ fine particles as a spraying abrasive in a proportion of the total amount with water is sprayed at a spraying pressure of 0.1 to 0.15 MPa. The surface of the lower layer is smoothed by applying wet blasting, and then a fine l-TiC layer is formed by vapor deposition under the conditions shown in Table 3 and the target layer thickness shown in Table 4.
(C) Further, a granular Ti compound (TiC, TiN, TiCN) layer is formed by vapor deposition under the conditions shown in Table 2 and the target layer thickness shown in Table 4.
(D) By repeating the vapor deposition formation of the fine l-TiC layer in (b) and the vapor deposition formation of the granular Ti compound (TiC, TiN, TiCN) layer in (c) until the target total layer thickness is reached. The intermediate layer is deposited,
(E) Furthermore, if necessary, an adhesion layer composed of either a TiCO layer or a TiCNO layer is formed by vapor deposition with a target layer thickness shown in Table 4,
(F) Next, by depositing an Al ₂ O ₃ layer under the conditions shown in Table 2 and the target layer thickness shown in Table 4,
Invention coated tools 1-12 were produced.

Moreover, for the purpose of comparison, the surface of the tool bases A to F is shown in Table 2 as the lower layer, intermediate layer (and adhesion layer) and upper layer of the hard coating layer, respectively, using a normal chemical vapor deposition apparatus. A lower layer made of a TiN layer is formed by vapor deposition under the conditions and the target layer thickness shown in Table 5,
Next, an intermediate layer composed of an 1-TiCN layer divided vertically by a TiN layer under the conditions shown in Table 2 and the target layer thickness shown in Table 5 is formed by vapor deposition.
Next, if necessary, an adhesion layer composed of either a TiCO layer or a TiCNO layer is formed by vapor deposition with a target layer thickness shown in Table 5,
Furthermore, by vapor-depositing an upper layer composed of an Al ₂ O ₃ layer under the conditions shown in Table 2 and the target layer thickness shown in Table 5,
Comparative coated tools 1-12 were produced.
(Comparative coated tools 1 to 12 are different from the inventive coated tools 1 to 12 in the structure of the intermediate layer.)

When the layer thicknesses of the constituent layers of the inventive coated tools 1 to 12 and the comparative coated tools 1 to 12 were measured using a scanning electron microscope, all of them substantially correspond to the target layer thicknesses shown in Tables 4 and 5. The same average layer thickness was shown.
Moreover, about the fine grain 1-TiC layer and granular TiC layer which are the intermediate | middle layers of this invention coated tool 1-12, using a transmission electron microscope (TEM), the crystal grain in the surface parallel to the tool base | substrate surface is used. The average crystal grain size was measured. The values are shown in Table 4.
The average grain size in this invention is measured by drawing a line parallel to the surface of the tool base at the center in the layer thickness direction of each layer, and calculating the length of the parallel line from the grain boundary intersecting the line. The value obtained by dividing the number of intersection points was used as the crystal grain size value. Further, the crystal grain size values were determined at at least five positions, and the average value was calculated to obtain the average crystal grain size value.

Next, a high-speed milling test was performed on the above-described coated tools 1 to 12 and comparative coated tools 1 to 12 under the following cutting conditions A and B.
<Cutting condition A>
Work material: Block material of JIS / SCM440 Cutting speed: 350 m / min,
Incision: 2 mm,
Single blade feed rate: 0.2 mm / tooth,
Cutting time: 10 minutes,
Wet high-speed milling cutting test of alloy steel under the conditions (normal cutting speed is 200 m / min),
<Cutting condition B>
Work material: Block material of JIS / FCD700 Cutting speed: 350 m / min,
Incision: 2 mm,
Single blade feed rate: 0.2 mm / tooth,
Cutting time: 8 minutes,
Wet high-speed milling cutting test of ductile cast iron under the conditions (normal cutting speed is 200 m / min),
In each cutting test, the flank wear width of the cutting edge was measured. The measurement results are shown in Table 6.

From the results shown in Tables 4 to 6, as the hard coating layer, on the lower layer made of the TiN layer, an intermediate layer composed of an alternately laminated structure of a fine l-TiC layer and a granular Ti compound (TiC, TiN, TiCN) layer The coated tool of the present invention in which a layer is formed by vapor deposition, and if necessary, an adhesion layer composed of a TiCO layer and a TiCNO layer is deposited, and an upper layer composed of an Al ₂ O ₃ layer is deposited thereon. In particular, since the intermediate layer consisting of alternating layers has the action of suppressing the progress and propagation of cracks, chipping, chipping, chipping, chipping, chipping, chipping, chipping, While providing excellent wear resistance over a long period of use without causing abnormal damage such as peeling, and extending the life of the coated tool, the intermediate layer is divided into upper and lower parts by the TiN layer. The -The comparative coated tool consisting of a TiCN layer does not have sufficient action to suppress the progress / propagation of cracks generated in the layer, so that the service life is short due to chipping, chipping, etc., and the wear resistance is inferior. It was.

  As described above, the coated tool of the present invention exhibits excellent chipping resistance and chipping resistance in high-speed milling cutting that receives a large thermal shock with high heat generation such as steel and cast iron, and prolongs the service life. In addition, it has excellent chipping resistance, chipping resistance, wear resistance, etc. even when used for continuous cutting and intermittent cutting as a cutting tool for turning and drilling. It can be fully satisfied with energy saving and energy saving.

Claims (2)

On the surface of the tool base composed of tungsten carbide based cemented carbide or titanium carbonitride based cermet,
(A) a lower layer composed of a nitride layer of Ti having an average layer thickness of 0.1 to 2 μm,
(B) a carbide layer of Ti having a fine grain vertically grown crystal structure and having an average layer thickness of 0.5 to 3 μm;
A Ti compound layer having a granular crystal structure composed of one or more of a Ti carbide layer, a nitride layer, and a carbonitride layer, and having an average layer thickness of 0.2 to 1 μm;
An intermediate layer having a total average layer thickness of 3 to 10 μm, comprising an alternating laminated structure with
(C) an aluminum oxide layer having an average layer thickness of 0.5 to 5 μm,
A surface-coated cutting tool, wherein the hard coating layer constituted by the above (a) to (c) is formed with a total average layer thickness of 4 to 15 μm.   Between the intermediate layer of the above (b) and the aluminum oxide layer of the above (c), it is composed of one of Ti carbonate layer and carbonitride oxide layer, and has an average layer thickness of 0.1 to 1 μm The surface-coated tool according to claim 1, further comprising an adhesion layer having an interposition.