JP2004122269A - Surface coated cermet cutting tool exhibiting superior chipping resistance under high speed heavy duty cutting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface coated cermet cutting tool exhibiting superior chipping resistance under high speed heavy duty cutting. <P>SOLUTION: This surface coated cermet cutting tool is formed by vapor depositing the hard coated layer of 10-35μm in the whole average layer thickness composed of (a) one layer or more of Ti compound layers and (b) α type aluminium oxide layer on the surface of a cermet base, and the average layer thickness of the α type aluminium oxide layer is set to 5-20μm. The intermediate part in the layer thickness direction equivalent to the thickness of 25-55% in terms of a ratio of occupying the average layer thickness of the α type aluminium oxide layer is composed of heating transformation α type aluminium oxide formed by heat-transforming aluminium oxide having κ type or θ type crystal structure in the state formed by vapor deposition and making the crystal structure into the α type crystal structure. The residual upper part and the lower part in the layer thickness direction are composed of vapor deposited α type aluminium oxide having the α type crystal structure in the state formed by vapor deposition. <P>COPYRIGHT: (C)2004,JPO

Description

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【発明の効果】
表４〜９に示される結果から、本発明被覆サーメット工具１〜１６は、いずれも硬質被覆層のα型Ａｌ_２Ｏ_３層を厚膜化した状態で、高い熱的機械的衝撃を伴なう高速重切削加工条件で、鋼や鋳鉄の切削加工を行なっても前記α型Ａｌ_２Ｏ_３層における加熱変態α型Ａｌ_２Ｏ_３の存在によって前記α型Ａｌ_２Ｏ_３層は引張残留応力のきわめて低い状態となっているので、切刃部にチッピングの発生なく、すぐれた耐摩耗性を発揮するのに対して、硬質被覆層のα型Ａｌ_２Ｏ_３層全体が蒸着α型Ａｌ_２Ｏ_３層で構成された従来被覆サーメット工具１〜１６においては、前記蒸着α型Ａｌ_２Ｏ_３層が具備する高い引張残留応力によって切刃部にチッピングが発生し易くなり、比較的短時間で使用寿命に至ることが明らかである。
上述のように、この発明の被覆サーメット工具は、各種の鋼や鋳鉄などの通常の条件での連続切削や断続切削加工は勿論のこと、特に高い熱的機械的衝撃を伴なう高速重切削加工に用いた場合にも、切刃部にチッピングの発生なく、長期に亘ってすぐれた切削性能を発揮するものであるから、切削加工装置の高性能化に十分満足に対応でき、かつ切削加工の一段の省力化および省エネ化、さらに低コスト化にも寄与するものである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention has an extremely small residual tensile stress in an aluminum oxide layer having an α-type crystal structure (hereinafter, referred to as α-type Al ₂ O ₃ ) constituting a hard coating layer. Therefore, it is possible to cut various kinds of steel and cast iron. A surface in which the cutting edge portion exhibits excellent chipping resistance even when the α-type Al ₂ O ₃ layer is thickened and the cutting is performed under high-speed heavy cutting conditions accompanied by high thermal mechanical shock. The present invention relates to a coated cermet cutting tool (hereinafter, referred to as a coated cermet tool).
[0002]
[Prior art]
Conventionally, generally, a surface of a cermet substrate formed of a tungsten carbide (hereinafter, referred to as WC) -based cemented carbide or a titanium cermet (hereinafter, referred to as TiCN) -based cermet,
(A) All have an average layer thickness of 0.5 to 15 μm, and are formed by vapor-deposited Ti carbide (hereinafter, indicated by TiC) layer, nitride (hereinafter, also indicated by TiN) layer, carbonitride (Hereinafter, referred to as TiCN) layer, a carbon oxide (hereinafter, referred to as TiCO) layer, and one or more Ti compound layers (hereinafter, referred to as TiCNO) layers of a carbonitride oxide (hereinafter, referred to as TiCNO) layer These are collectively called Ti compound layer),
(B) a vapor-deposited α-type aluminum oxide layer having an average layer thickness of 1 to 5 μm and having an α-type crystal structure in a vapor-deposited state (hereinafter referred to as a vapor-deposited α-type Al ₂ O ₃ layer);
It is also known that a coated cermet tool formed by forming a hard coating layer composed of, and that this coated cermet tool is used for continuous cutting or interrupted cutting of, for example, various types of steel or cast iron. (For example, see Patent Document 1).
[0003]
Further, generally, the Ti compound layer or the vapor deposited α-type Al ₂ O ₃ layer constituting the hard coating layer of the above-mentioned coated cermet tool has a granular crystal structure, and further, the TiCN layer constituting the Ti compound layer is formed as a layer. For the purpose of improving its toughness, using a mixed gas containing organic carbonitride as a reaction gas with a normal chemical vapor deposition apparatus, it is formed by chemical vapor deposition at a medium temperature range of 700 to 950 ° C. to grow vertically. It is also known to have a crystal structure (see Patent Documents 2 and 3).
[0004]
[Patent Document 1]
JP-A-6-31503 [Patent Document 2]
JP-A-6-8010 [Patent Document 3]
JP-A-7-328808
[Problems to be solved by the invention]
On the other hand, in recent years, there has been a strong demand for labor saving, energy saving, and further cost reduction of the cutting process, and in conjunction with the high performance of the cutting device, the deposition α-type Al ₂ layer forming the hard coating layer has been strongly required. The O ₃ layer not only deepens the tendency of thicker film, but also the cutting process tends to be performed at high speed and under heavy cutting conditions such as high cutting and high feed. However, in the conventional coated cermet tool described above, There is no problem when this is used for continuous cutting or intermittent cutting under ordinary conditions such as steel or cast iron, but this is particularly effective when the vapor deposited α-type Al ₂ O ₃ layer is formed into a thick film at a high speed heavy load. When used under cutting conditions, the deposited α-type Al ₂ O ₃ layer has an extremely high tensile residual stress, so that high thermal mechanical shock generated during cutting causes chipping (small chipping) at the cutting edge. Easier, this result Since 耗進 row is to be promoted, at present, leading to a relatively short time service life.
[0006]
[Means for Solving the Problems]
In view of the above, the present inventors have found that even when the hard coating layer is used for high-speed heavy cutting in a state where the α-type Al ₂ O ₃ layer is thickened, the cutting edge portion has excellent resistance. As a result of research to develop a coated cermet tool that demonstrates chipping properties,
In the state where the total average layer thickness of the α-type Al ₂ O ₃ layer constituting the hard coating layer of the coated cermet tool is increased to 5 to 20 μm, the upper part and the lower part in the layer thickness direction are formed under normal conditions. constituted by depositing α-type Al ₂ O ₃ was deposited form, the intermediate portion of the layer thickness direction, in percentage of the total average layer thickness of the α-type the Al ₂ O ₃ layer, a thickness corresponding to 25 to 55% Heat-transformed α-type Al ₂ O ₃ , that is, Al ₂ O ₃ having a κ-type or θ-type crystal structure formed by vapor deposition under ordinary conditions, heat treatment, preferably in an Ar atmosphere, at a temperature of 1000 ° C. As described above, when a heat treatment is performed under the condition of holding for a predetermined time to constitute the heat-transformed α-type Al ₂ O ₃ obtained by transforming the κ-type or θ-type crystal structure into an α-type crystal structure, a thick film as a result is obtained. the phased α type the Al ₂ O ₃ layer, the heating transformation α type to configure this by l ₂ O _3, the tensile residual stress is to that significantly reduced, thus constituting α-type _{the Al} 2 _{O 3} layer of the hard coating layer by vapor α-type _Al 2 _{O 3} and the heating transformation α-type _Al 2 _{O 3} of the In the coated cermet tool, the occurrence of chipping in the cutting edge portion is significantly suppressed even when the α-type Al ₂ O ₃ layer is thickened and used under high-speed heavy cutting conditions. The research results showed that the machine would exhibit excellent cutting performance throughout.
[0007]
The present invention has been made based on the results of the above-described research, and has the following features:
(A) a Ti compound layer composed of one or more of a TiC layer, a TiN layer, a TiCN layer, a TiCO layer, and a TiCNO layer;
(B) α-type Al ₂ O ₃ layer,
In a coated cermet tool formed by vapor-depositing a hard coating layer composed of with a total average layer thickness of 10 to 35 μm,
The average layer thickness of the α-type Al ₂ O ₃ layer is 5 to 20 μm, and the middle portion in the layer thickness direction is equivalent to 25 to 55% in the average layer thickness of the α-type Al ₂ O ₃ layer. A heat transformation is performed on an aluminum oxide having a κ-type or θ-type crystal structure (hereinafter, referred to as Al ₂ O ₃ ) in a vapor-deposited state to obtain a α-type crystal structure. composed of α-type Al ₂ O _3, the remainder of the layer thickness direction in the upper part and the lower part, formed by constituted by depositing α-type Al ₂ O ₃ having a α-type crystal structure in a state of being vapor deposited,
It is characterized by a coated cermet tool that demonstrates excellent chipping resistance in high-speed heavy cutting.
[0008]
The reason why the average layer thickness of the constituent layers of the hard coating layer of the coated cermet tool of the present invention is limited as described above is as follows.
(A) Average layer thickness of α-type Al ₂ O ₃ layer If the average layer thickness is less than 5 μm, the thickness of the layer is insufficient, and it is not possible to achieve a satisfactory life extension of the service life. If it exceeds 20 μm, chipping is likely to occur in the cutting edge portion. Therefore, the average layer thickness is set to 5 to 20 μm.
[0009]
(B) the percentage heating transformation α-type _Al 2 _{O 3} accounts for α type _{the Al} 2 _{O 3} layer of heat transformation α-type _Al 2 _{O 3} is the α type _{the Al} 2 _{O 3} layer generally by the presence of this as above It has the effect of reducing the tensile residual stress as compared with the case where it is made of vapor-deposited α-type Al ₂ O ₃ , but its thickness ratio is less than 25% in the average layer thickness of the α-type Al ₂ O ₃ layer. However, if the thickness ratio exceeds 55%, the strength of the layer itself drops sharply, which causes chipping at the cutting edge. Therefore, the thickness ratio of the α-type Al ₂ O ₃ layer is determined to be 25 to 55% in terms of the average layer thickness.
[0010]
(C) Average Layer Thickness of Hard Coating Layer If the average layer thickness is less than 10 μm, sufficient service life cannot be ensured. On the other hand, if the average layer thickness exceeds 35 μm and becomes too thick, the cutting edge portion Since chipping easily occurs, the average layer thickness is set to 10 to 35 μm.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the coated cermet tool of the present invention will be specifically described with reference to examples.
As raw material powders, WC powders each having a predetermined average particle size in the range of 0.5 to 4 μm, (Ti, W) C (the same hereinafter, TiC / WC = 30/70 by mass ratio) powder, Ti, W) CN (TiC / TiN / WC = 24/20/56) powder, (Ta, Nb) C (TaC / NbC = 90/10) powder, Cr ₃ C ₂ powder, and Co powder, These raw material powders were blended in the composition shown in Table 1, wet-mixed in a ball mill for 72 hours, dried, and then pressed into a green compact of a predetermined shape at a pressure of 98 MPa. Medium, vacuum sintering at 1410 ° C. for 1 hour, and after sintering, a WC having a throw-away tip shape specified in ISO · CNMG120408 by performing honing processing on the cutting edge with an R: 0.08 mm. Base cemented carbide Configured cermet substrate A~F were prepared, respectively.
[0012]
Further, as raw material powders, TiCN (TiC / TiN = 50/50 by mass ratio) powder, Mo ₂ C powder, ZrC powder, NbC powder, TaC powder, WC powder each 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 in a ball mill for 24 hours, dried, and pressed into a green compact at a pressure of 98 MPa. This green compact was sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour, and after sintering, the cutting edge was subjected to a honing process of R: 0.08 mm to obtain an ISO. Cermet bases a to f composed of TiCN-based cermets having a chip shape of standard CNMG120412 were formed.
[0013]
Next, the surfaces of the cermet substrates A to F and the cermet substrates a to f were ultrasonically cleaned in acetone, dried, and then dried using an ordinary chemical vapor deposition apparatus in Table 3 (l-TiCN in Table 3). Indicates the conditions for forming a TiCN layer having a vertically elongated crystal structure described in, for example, JP-A-6-8008, and the others indicate conditions for forming a normal granular crystal structure.) Under the conditions, each of the combinations shown in Tables 4 and 5, a Ti compound layer having the target layer thickness also shown in Tables 4 and 5, and a heat-transformed α-type Al ₂ O ₃ and a vapor-deposited α-type Al ₂ O ₃ have been α-type the Al ₂ O ₃ layer deposited forming a hard coating layer composed of (in this case the heating transformation α-type Al ₂ O ₃ is first table 3 crystal structure κ-type or θ-type under the conditions shown in Al ₂ the O ₃ was vapor deposited, to which a It is formed by subjecting the κ-type or θ-type crystal structure to an α-type crystal by performing a heat treatment in an atmosphere at a temperature of 1050 ° C. for a predetermined time within a range of 1 to 8 hours. ) To produce coated cermet tools 1 to 16 of the present invention.
For the purpose of comparison, as shown in Tables 6 and 7, except that the entire α-type Al ₂ O ₃ layer of the hard coating layer is also a vapor-deposited α-type Al ₂ O ₃ layer having an average layer thickness also shown in Table 6. Manufactured the conventional coated cermet tools 1 to 16 under the same conditions.
[0014]
The thicknesses of the constituent layers of the hard coating layer of the coated cermet tools 1 to 16 of the present invention and the conventional coated cermet tools 1 to 16 obtained as described above were measured using a scanning electron microscope. Surface measurement), all showed an average layer thickness substantially equal to the target layer thickness (average value of five-point measurements).
[0015]
Next, the above coated cermet tools 1 to 8 of the present invention and the conventional coated cermet tools 1 to 8 in a state where each of the above various coated cermet tools was screwed to the tip of a tool steel tool with a fixing jig, Work material: JIS SCM440 round bar,
Cutting speed: 350m / min,
Cut: 6.5 mm,
Feed: 0.3 mm / rev,
Cutting time: 5 minutes,
Dry high-speed high-cut continuous cutting test of alloy steel under the following conditions:
Work material: JIS S45C lengthwise round bar with four equally spaced longitudinal grooves,
Cutting speed: 350m / min,
Cut: 1.5 mm,
Feed: 0.7mm / rev,
Cutting time: 3 minutes,
A dry high-speed high-feed intermittent cutting test of carbon steel was performed under the following conditions.
[0016]
Further, for the coated cermet tools 9 to 16 of the present invention and the conventional coated cermet tools 9 to 16,
Work material: JIS SCM440 round bar,
Cutting speed: 400m / min,
Cut: 1.0 mm,
Feed: 0.7mm / rev,
Cutting time: 5 minutes,
Dry high-speed high-feed continuous cutting test of alloy steel under the conditions of
Work material: JIS S45C lengthwise round bar with four equally spaced longitudinal grooves,
Cutting speed: 400m / min,
Cut: 5.5 mm,
Feed: 0.25 mm / rev,
Cutting time: 3 minutes,
A dry high-speed, high-cut intermittent cutting test was performed on carbon steel under the following conditions, and the flank wear width of the cutting edge was measured in each cutting test. Tables 8 and 9 show the measurement results.
[0017]
[Table 1]

[0018]
[Table 2]

[0019]
[Table 3]

[0020]
[Table 4]

[0021]
[Table 5]

[0022]
[Table 6]

[0023]
[Table 7]

[0024]
[Table 8]

[0025]
[Table 9]

[0026]
【The invention's effect】
From the results shown in Tables 4 to 9, all of the coated cermet tools 1 to 16 of the present invention are accompanied by high thermal mechanical impact in a state where the α-type Al ₂ O ₃ layer of the hard coating layer is thickened. cormorant fast heavy cutting conditions, the α type the Al ₂ O ₃ layer is tensile residual stress by the presence of heat transformation α-type Al ₂ O ₃ be subjected to machining of steel and cast iron in the α-type the Al ₂ O ₃ layer Is extremely low, so that the cutting edge portion exhibits excellent wear resistance without chipping, whereas the hard coating layer α-type Al ₂ O ₃ layer is entirely vapor-deposited α-type Al ₂ O _3. In the conventional coated cermet tools 1 to 16 composed of the O ₃ layer, chipping easily occurs in the cutting edge portion due to the high tensile residual stress of the vapor-deposited α-type Al ₂ O ₃ layer. It is clear that the service life will be reached.
As described above, the coated cermet tool of the present invention can be used not only for continuous cutting and interrupted cutting under ordinary conditions such as various kinds of steel and cast iron, but also for high-speed heavy cutting particularly involving high thermal mechanical impact. Even when used for machining, it has excellent cutting performance over a long period of time without chipping on the cutting edge, so it can respond satisfactorily to the high performance of cutting equipment and cutting. It also contributes to further labor saving, energy saving and cost reduction.

Claims (1)

On the surface of a cermet substrate composed of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet,
(A) a Ti compound layer composed of one or more of a Ti carbide layer, a nitride layer, a carbonitride layer, a carbonate layer, and a carbonitride layer;
(B) an aluminum oxide layer having an α-type crystal structure,
In a surface-coated cermet cutting tool formed by vapor-depositing a hard coating layer composed of 10 to 35 μm with an overall average layer thickness of:
The average thickness of the aluminum oxide layer having the α-type crystal structure is 5 to 20 μm, and a middle portion in the thickness direction of the aluminum oxide layer corresponds to 25 to 55% in the average layer thickness of the α-type aluminum oxide layer. Heat-transformed α-type aluminum oxide having a κ-type or θ-type crystal structure in a state where the thickness is vapor-deposited to form an α-type crystal structure by subjecting the oxide layer to a heat-transformation treatment. The upper part and the lower part in the thickness direction are made of vapor-deposited α-type aluminum oxide having an α-type crystal structure in a vapor-deposited state,
A surface-coated cermet cutting tool that exhibits excellent chipping resistance in high-speed heavy cutting.