JP2010274330A - Surface coated cutting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface-coated cutting tool that exhibits excellent welding resistance and chipping resistance with a hard coating layer in intermittent heavy cutting of difficult-to-cut materials that are likely to be welded.
In a surface-coated cutting tool formed by vapor-depositing a hard coating layer on the surface of a tool substrate, the lower layer is composed of a Ti compound layer, and the upper layer has an average layer thickness of 0.8 to 1 in one layer. .5 μm aluminum oxide layer and a titanium-containing aluminum oxide layer having an average layer thickness of 0.3 to 0.5 μm are alternately laminated, and the titanium content in the titanium-containing aluminum oxide layer is the thickness direction. And the maximum value is 2 to 5 atomic% in the intermediate region in the layer thickness direction.
[Selection figure] None

Description

  In the present invention, the upper layer of the hard coating layer is configured as an alternately laminated structure of an aluminum oxide layer and a titanium-containing aluminum oxide layer, and the composition ratio of Ti content in the titanium-containing aluminum oxide layer is changed in the layer thickness direction. In the intermittent heavy cutting of difficult-to-cut materials with high weldability, such as mild steel and stainless steel, it prevents long-term welding and prevents chipping (microchips) from occurring at the cutting edge. The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits excellent cutting performance over a long period of time.

Conventionally, a substrate composed of a tungsten carbide group (hereinafter referred to as a WC group) cemented carbide or a titanium carbonitride group (hereinafter referred to as a TiCN group) cermet (hereinafter collectively referred to as a tool substrate). As a hard coating layer on the surface,
Ti carbide (hereinafter referred to as TiC) layer, nitride (hereinafter also referred to as TiN) layer, carbonitride (hereinafter referred to as TiCN) layer, carbonate (hereinafter referred to as TiCO) layer, and carbonitride A Ti compound layer composed of one or more of oxide (hereinafter referred to as TiCNO) layers, a lower layer,
An aluminum oxide layer containing titanium as an upper layer,
The coating tool (patent documents 1-3) formed as is known.

  Furthermore, in these coated tools, in order to improve the toughness during high-speed cutting, the upper layer of the hard coating layer is, for example, a Ti compound layer and an aluminum oxide layer or Ti oxide that dissolves Ti oxide. It is also known to form a laminated structure with an aluminum oxide layer coexisting therein (Patent Documents 4 and 5) and to constitute a laminated structure of a titanium trioxide main layer and an aluminum oxide layer (Patent Document 6). .

Japanese Patent Publication No. 61-15149 JP 2002-205205 A JP 2008-73847 A Japanese Examined Patent Publication No. 62-6748 Japanese Patent Publication No. 5-49750 Japanese Patent No. 3430939

  In recent years, there has been a strong demand for energy saving and labor saving of cutting work, and accordingly, cutting conditions have become more severe. There is no special problem in normal machining such as cast iron or cast iron, but when this is used for intermittent heavy cutting of difficult-to-cut materials with high weldability, such as mild steel and stainless steel, the cutting edge As a result of the occurrence of chip welding to the cutting edge and the repeated large impact and mechanical load on the cutting edge, the toughness is insufficient and chipping occurs at the cutting edge. At present, the service life is reached in a relatively short time.

  In view of the above, the present inventors have excellent chipping resistance and wear resistance even in intermittent heavy cutting of difficult-to-cut materials such as high weldability mild steel and stainless steel, and prolong tool life. As a result of conducting research by focusing on the upper layer of the hard coating layer, the following knowledge was obtained.

First, since an aluminum oxide layer containing titanium (hereinafter referred to as a Ti-containing Al ₂ O ₃ layer) has excellent toughness, an aluminum oxide layer (hereinafter referred to as an Al ₂ O ₃ layer) and a Ti-containing Al _When the upper layer of the hard coating layer is constituted by alternately laminating the ₂ O ₃ layers, and the coated tool having such an upper layer is applied to intermittent heavy cutting of difficult-to-cut materials, the Ti-containing Al ₂ O ₃ layer the presence of, although the toughness of the upper layer is improved, on the other hand, compared with the case of the Al ₂ O ₃ layer single layer, reduces the high-temperature hardness of the upper layer, further, the Al ₂ O ₃ layer and Ti-containing Adhesion strength with the Al ₂ O ₃ layer is not sufficient, and delamination is likely to occur. Therefore, it is possible to improve chipping resistance and wear resistance by the occurrence of high heat welding and impact / mechanical load on the cutting edge. I understood that I could not expect it.

Therefore, the present inventors have made further studies, and as a result, the Ti-containing Al ₂ O ₃ layer is not configured as a layer having a uniform composition, but the Ti content ratio gradually changes along the layer thickness direction. Further, it is configured to be a layer having a uniform composition, and further, an intermediate region of each Ti-containing Al ₂ O ₃ layer (for example, the thickness of the Ti-containing Al ₂ O ₃ layer is t (where t is 0.3 to 0.00). In the intermediate region corresponding to the layer thickness of t / 3), and the maximum value of the Ti content is 2 to 5 atomic%. A non-uniform composition Ti-containing Al ₂ O ₃ layer (hereinafter referred to as composition-change Ti-containing Al ₂ O ₃ layer) is formed, and Al ₂ O ₃ layers and composition-change Ti-containing Al ₂ O ₃ layers are alternately laminated. When the upper layer is formed, the upper layer has not only reduced hardness at high temperatures but also has a composition. When the Ti contained in the changed Ti-containing Al ₂ O ₃ layer forms rutile-type Ti oxide (TiO ₂ ) at the time of cutting, the lubricity is enhanced, and the Al ₂ O ₃ layer and the composition changed Ti-containing Al It has been found that the interlayer adhesion strength with the ₂ O ₃ layer is also improved.

Therefore, as a hard coating layer, a coated tool coated with a lower layer made of a Ti compound and an upper layer made up of alternating layers of an Al ₂ O ₃ layer and a composition-change Ti-containing Al ₂ O ₃ layer is a mild steel with high weldability. In intermittent heavy cutting of difficult-to-cut materials such as stainless steel, it has been found that chipping resistance and wear resistance are improved, excellent cutting performance is demonstrated over long-term use, and tool life is extended. It is.

This invention was made based on the above knowledge,
“It was composed of a lower layer having a layer thickness of 1 to 15 μm and an upper layer having a layer thickness of 3 to 15 μm on the surface of the tool base made of tungsten carbide base cemented carbide or titanium carbonitride base cermet. In a surface-coated cutting tool formed by vapor-depositing a hard coating layer,
The lower layer is composed of a Ti compound layer composed of one or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer and carbonitride layer,
Further, the upper layer, as the alternating layered structure of the more the Al ₂ O ₃ layer having an average layer thickness 0.8~1.5μm the average layer thickness 0.3 to 0.5 [mu] m Ti containing the Al ₂ O ₃ layer of Configured,
Furthermore, the Ti content ratio in the Ti-containing Al ₂ O ₃ layer shows a composition change that maximizes the Ti content ratio in the intermediate region in the layer thickness direction, and the maximum value of the Ti content ratio is 2 A surface-coated cutting tool, which is ˜5 atomic%. "
It has the characteristics.

The hard coating layer of the coated tool of the present invention will be described in detail below.
(A) Ti compound layer constituting the lower layer:
Ti composed of one or more of Ti carbide (TiC) layer, nitride (TiN) layer, carbonitride (TiCN) layer, carbonate (TiCO) layer and carbonitride oxide (TiCNO) layer For example, the compound layer can be formed by vapor deposition under normal chemical vapor deposition conditions, and the lower layer made of the Ti compound layer adheres firmly to both the tool base and the upper layer, and the tool base of the hard coating layer. In addition to contributing to the improvement in adhesion, the hard coating layer itself has a high temperature strength due to the presence of the high temperature strength.
However, if the layer thickness of the entire lower layer is less than 1 μm, the above-mentioned effect cannot be fully exerted. On the other hand, if the layer thickness exceeds 15 μm, a large impact / mechanical load acts repeatedly on the cutting edge. Since it becomes easy to cause thermoplastic deformation by intermittent heavy cutting, and this causes uneven wear, the layer thickness of the entire lower layer is set to 1 to 15 μm.

(B) Al ₂ O ₃ layers constituting the alternating stack of upper layers:
The Al ₂ O ₃ layer constituting the alternately laminated structure of the upper layer can be formed by vapor deposition by a normal chemical vapor deposition method as already well known.
For example, with a normal chemical vapor deposition device,
Reaction gas composition: by _{volume%, AlCl 3: 6~10%,} CO 2: 10~15%, HCl: 3~5%, H 2 S: 0.05~0.2%, H 2: remainder,
Reaction atmosphere temperature: 900-1020 ° C.
Reaction atmosphere pressure: 3 to 5 kPa,
The α-type Al ₂ O ₃ layer can be formed by vapor deposition under the conditions described above.
The α-type Al ₂ O ₃ layer has excellent high-temperature hardness and heat resistance, and functions as a layer for ensuring wear resistance in intermittent heavy cutting.
However, if the average layer thickness of the α-type Al ₂ O ₃ layers constituting the alternately laminated structure is less than 0.8 μm, sufficient high-temperature hardness and heat resistance cannot be imparted to the upper layer. If the average layer thickness exceeds 1.5 μm, the toughness decreases due to the growth of coarse crystal grains and chipping is likely to occur. Therefore, the average layer thickness of the Al ₂ O ₃ layer is determined to be 0.8 to 1.5 μm. .
As the Al ₂ O ₃ layer, not only an α-type Al ₂ O ₃ layer but also a κ-type or θ-type Al ₂ O ₃ layer has no problem.

(C) Composition-changing Ti-containing Al ₂ O ₃ layer constituting an alternating stack of upper layers:
The composition change Ti-containing Al ₂ O ₃ layer
Reaction gas composition: by _{volume%, AlCl 3: 3~7%,} TiCl 4: 0.3~0.5%, CO 2: 10~15%, HCl: 3~5%, H 2 S: 0.05 _{~0.08%, AlI 3: 0.5~1.0%} , H 2: remainder,
Reaction atmosphere temperature: 900-1020 ° C.
Reaction atmosphere pressure: 3 to 5 kPa,
Deposition starts under the conditions of
Next, as the vapor deposition proceeds, the content ratio of the TiCl ₄ gas component in the reaction gas is increased, and the reaction gas containing TiCl ₄ : 0.8 to 1.0% allows the Ti content ratio to be maximized. The intermediate region is formed by vapor deposition,
Next, in the latter stage of vapor deposition, the content ratio of the TiCl ₄ gas component is gradually decreased, the vapor deposition is terminated in a reaction gas containing TiCl ₄ : 0.3 to 0.5%, and the composition change Ti-containing Al ₂ O _3. By forming the layer, a composition-change Ti-containing Al ₂ O ₃ layer can be formed by vapor deposition.
Then, the formation of the Al ₂ O ₃ layer having a predetermined average layer thickness according to (b) and the formation of the Ti-containing Al ₂ O ₃ layer having the predetermined layer average layer thickness according to (c) are alternately performed. Then, an upper layer composed of an alternately laminated structure having a predetermined layer thickness is formed.

Ti content in the layer thickness direction position in the change in composition Ti-containing Al ₂ O ₃ layer as described above, is affected by the content of TiCl ₄ in the reaction gas during deposition, change in composition Ti-containing Al ₂ O ₃ An intermediate region in the layer (for example, in the case of a composition-change Ti-containing Al ₂ O ₃ layer having a layer thickness of 0.3 μm, 1/3 of the thickness, that is, a thickness of 0.1 μm at the center in the layer thickness direction) The Ti content ratio in the above region) needs to be 2 to 5 atomic% in a ratio (Ti × 100 / (Al + Ti)) to the total amount with Al. When the maximum Ti content in the intermediate region of the composition-change Ti-containing Al ₂ O ₃ layer is less than 2 atomic%, the effect of improving chipping resistance is small because the effect of improving the toughness of the upper layer due to the Ti content is small. Since there is little formation of type Ti oxide (TiO ₂ ), it is difficult to expect an improvement in lubricity during cutting. On the other hand, when the maximum Ti content ratio in the intermediate region in the composition-change Ti-containing Al ₂ O ₃ layer exceeds 5 atomic%, the adhesion strength with the Al ₂ O ₃ layers constituting the alternate lamination is lowered, and the high-temperature hardness of the upper layer Further, precipitation of coarse Ti compounds at the Al ₂ O ₃ grain boundaries occurs, and the grain boundary strength decreases, which is disadvantageous in terms of chipping resistance and wear resistance. . Therefore, the maximum Ti content ratio in the intermediate region in the Al ₂ O ₃ layer is set to 2 to 5 atomic%.
Further, the interface to the interface between the Al ₂ O ₃ layer adjacent to the composition change Ti containing the Al ₂ O ₃ layer, but the diffusion of Ti from compositional changes Ti containing the Al ₂ O ₃ layer is produced, the Al ₂ O ₃ layer Since the composition change Ti-containing Al ₂ O ₃ layer in the vicinity has a small Ti content ratio (the content ratio of the TiCl ₄ gas component in the reaction gas is small in the early and late deposition periods), the interlayer adhesion strength in the alternating lamination is very high And delamination does not occur.

When the average layer thickness of the composition-changed Ti-containing Al ₂ O ₃ layers constituting the alternately laminated structure is less than 0.3 μm, the effects of improving toughness and lubricity are not sufficient, while the average layer thickness is 0.1. If it exceeds 5 μm, wear resistance and chipping resistance deteriorate due to a decrease in high-temperature hardness and an interlayer adhesion strength as an entire upper layer composed of an alternately laminated structure, so the composition change of Ti-containing Al ₂ O ₃ layer The average layer thickness was determined to be 0.3 to 0.5 μm.

(D) Upper layer having an alternate layer structure An upper layer is formed as an alternate layer structure of an Al ₂ O ₃ layer having a predetermined average layer thickness and a Ti-containing Al ₂ O ₃ layer having a predetermined layer average layer thickness. However, if the layer thickness of the upper layer as a whole is less than 3 μm, excellent wear resistance cannot be exhibited over a long period of use, while if the layer thickness exceeds 15 μm, chipping or the like is likely to occur. Therefore, the layer thickness of the entire upper layer was determined to be 3 to 15 μm.

In the coated tool of the present invention, the lower layer of the hard coating layer is composed of a Ti compound layer, and the upper layer is composed of an alternately laminated structure of Al ₂ O ₃ layers and composition-change Ti-containing Al ₂ O ₃ layers. As a result, the upper layer has excellent high-temperature hardness and heat resistance, as well as excellent chipping resistance, chipping resistance, peeling resistance, and lubricity, so that it has high weldability and Even when used for intermittent heavy cutting of difficult-to-cut materials such as mild steel and stainless steel, where large impact and mechanical loads repeatedly act on the cutting edge, abnormal damage such as chipping, chipping and peeling occurs. Without exhibiting excellent wear resistance over a long period of use.

  Next, the coated tool of the present invention will be specifically described with reference to examples.

As raw material powders, WC powder, TiC powder, ZrC powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder, and Co powder each having an average particle diameter of 1 to 3 μm are prepared. The raw material powder is blended in the blending composition shown in Table 1, added with wax, ball mill mixed in acetone for 24 hours, dried under reduced pressure, and press-molded into a green compact of a predetermined shape at a pressure of 98 MPa. The green compact is vacuum-sintered in a vacuum of 5 Pa at a predetermined temperature within a range of 1370 to 1470 ° C. for 1 hour. After sintering, the cutting edge is subjected to a honing process of R: 0.07 mm. Thus, tool bases A to F made of a WC-based cemented carbide having a throwaway tip shape specified in ISO · CNMG120408 were manufactured.

In addition, as raw material powders, TiCN (mass ratio TiC / TiN = 50/50) powder, Mo ₂ C powder, ZrC powder, NbC powder, TaC powder, WC powder, all having an average particle diameter of 0.5 to 2 μm. Co powder and Ni powder are prepared, and these raw material powders are blended in the blending composition shown in Table 2, wet mixed by a ball mill for 24 hours, dried, and pressed into a compact at a pressure of 98 MPa. The green compact was sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour, and after the sintering, the cutting edge portion was subjected to a honing process of R: 0.07 mm. Tool bases a to f made of TiCN-based cermet having a standard / CNMG12041 chip shape were formed.

  A normal chemical vapor deposition apparatus was used on the surfaces of the tool bases A to F and the tool bases a to f, and Table 3 (l-TiCN in Table 3 is a vertically elongated crystal described in JP-A-6-8010). Ti compound layer having a target layer thickness shown in Table 5 under the conditions shown in Table 5 below. Was deposited as a lower layer of the hard coating layer.

Then, under the conditions shown in Table 3, while depositing the Al ₂ O ₃ layer more in average target layer thickness shown in Table 5 under the conditions shown in Table 4, in a more average target layer thickness shown in Table 5 Vapor deposition of a composition-change Ti-containing Al ₂ O ₃ layer,
Furthermore, repeated alternately deposited with the the Al ₂ O ₃ layer and the composition change Ti containing the Al ₂ O ₃ layer, depositing a top layer consisting of alternating laminated structure, such that the target layer thickness shown in Table 5 Formed and manufactured the inventive coated tools 1-13, respectively.

  For the purpose of comparison, a Ti compound layer having a target layer thickness shown in Table 6 is applied to the lower surface of the hard coating layer on the surfaces of the tool bases A to F and the tool bases a to f under the conditions shown in Table 3. Comparative coating tools 1 to 13 were produced by forming these upper layers by vapor deposition under the conditions deviating from the scope of the present invention (the same conditions as the lower layer formation of the present coated tools 1 to 13).

The composition change Ti containing _{the Al} 2 _{O 3} layer of the present invention coated tools 1 to 13, the maximum content of Ti (atomic%) were measured by Auger line analysis in the layer thickness direction.
The results are shown in Table 6.
In addition, regarding the comparative coated tool in which the composition-changed Ti-containing Al ₂ O ₃ layer or the uniform composition Ti-containing Al ₂ O ₃ layer is deposited as the upper layer, similarly, the Ti (maximum) content ratio (atomic%) It was measured by Auger line analysis in the thickness direction.
The results are shown in Table 7.

  Further, when the thicknesses of the constituent layers of the hard coating layers of the present coated tools 1 to 13 and the comparative coated tools 1 to 13 were measured using a scanning electron microscope (longitudinal cross section measurement), both of them were the target layer thickness. The substantially same average layer thickness (average value of 5-point measurement) was shown.

Next, in the state where all the above-mentioned various coated tools are screwed to the tip of the tool steel tool with a fixing jig, the present coated tools 1 to 13 and the conventional coated tools 1 to 13 are respectively An intermittent heavy cutting test was conducted under the cutting conditions A and B.
[Cutting conditions A]
Work material: JIS / S10C lengthwise equal length 4 round bar with round groove Cutting speed: 200 m / min,
Cutting depth: 2.0 mm,
Feed: 0.3 mm / rev. ,
Cutting time: 20 minutes,
Wet intermittent high cut cutting test of mild steel under the conditions of (normal cutting is 1.5 mm),
[Cutting conditions B]
Work material: JIS / SUS304 lengthwise equidistant four round grooved round bars Cutting speed: 150 m / min,
Cutting depth: 1.7 mm,
Feed: 0.45 mm / rev. ,
Cutting time: 18 minutes,
Stainless steel dry interrupted high feed cutting test under normal conditions (normal feed is 0.3 mm / rev.),
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 5 to 7, the coated carbide cutting tools 1 to 13 of the present invention have an upper layer of a hard coating layer as an alternately laminated structure of an Al ₂ O ₃ layer and a composition-change Ti-containing Al ₂ O ₃ layer. Constructed, the upper layer has excellent high temperature hardness, heat resistance, as well as excellent chipping resistance, chipping resistance, peeling resistance, lubricity, and thus it has high weldability and a cutting edge Even when used for intermittent heavy cutting of difficult-to-cut materials such as mild steel and stainless steel, where a large impact and mechanical load are repeatedly applied, without causing abnormal damage such as chipping, chipping, peeling, etc. Excellent wear resistance over a long period of use.
On the other hand, the upper layer of the hard coating layer is composed only of a composition change Ti-containing Al ₂ O ₃ layer, a uniform composition Ti-containing Al ₂ O ₃ layer, an Al ₂ O ₃ layer, etc. outside the scope of the present invention. The coated tools 1 to 13 were inferior in chipping resistance, wear resistance, etc., and had a short tool life.

  As described above, the coated tool of the present invention has excellent high-temperature hardness and heat resistance, as well as excellent chipping resistance, chipping resistance, peeling resistance, and lubricity, so that steel and cast iron under normal conditions In addition to continuous cutting and intermittent cutting of the above, even in the heavy cutting of difficult-to-cut materials, which are extremely severe cutting conditions, it exhibits excellent cutting performance over a long period without causing abnormal damage such as chipping. Therefore, it can cope with energy saving and labor saving of cutting work sufficiently satisfactorily.

Claims (1)

A hard surface composed of a lower layer having a layer thickness of 1 to 15 μm and an upper layer having a layer thickness of 3 to 15 μm on the surface of a tool base composed of a tungsten carbide-based cemented carbide or a titanium carbonitride-based cermet In a surface-coated cutting tool formed by vapor-depositing a coating layer,
The lower layer is composed of a Ti compound layer composed of one or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer and carbonitride layer,
Further, the upper layer is configured as an alternately laminated structure of an aluminum oxide layer having an average layer thickness of 0.8 to 1.5 μm and a titanium-containing aluminum oxide layer having an average layer thickness of 0.3 to 0.5 μm,
Further, the titanium content ratio in the titanium-containing aluminum oxide layer shows a composition change that maximizes the titanium content ratio in the intermediate region in the layer thickness direction, and the maximum value of the titanium content ratio is 2 to 5 A surface-coated cutting tool characterized in that it is atomic%.