JP2002239807A - Surface-covered thermet made cutting tool hard covered layer of which has excellent thermal shock resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface-covered thermet made cutting tool a hard covered layer of which has excellent thermal shock resistance. SOLUTION: The surface-covered thermet made cutting tool is constituted by forming the hard covered layer constituted of (a) a Ti compound layer constituted of lamination layers of one layer or more than two layers of a TiC layer, a TiN layer, a TiCN layer, a TiCO layer and a TiCNO layer evaporated and formed as a lower side layer and having average layer thickness of 3-20 μm as a lower side layer and (b) a composite double a type Al2O3 layer a lower part layer of which is α type crystal structured by applying heating transforming treatment on an Al2O3 layer of a κ type crystal structure in an evaporated and formed state, having a structure where a transformed crack made by the heating transforming treatment is uniformly dispersed and distributed and constituted of a transformed α type Al2O3 layer having average layer thickness of 3-15 μm and an evaporated α type Al2O3 layer of an αtype crystal structure evaporated and formed having average layer thickness of 0.5-2 μm on its upper layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a hard coating layer having excellent chipping resistance against thermal shocks repeatedly applied to a cutting edge portion at a very short pitch particularly at the time of high-speed interrupted cutting of steel or cast iron. That is, the present invention relates to a surface-coated cermet cutting tool having a hard coating layer having excellent thermal shock resistance (hereinafter referred to as a coated cermet tool).

[0002]

2. Description of the Related Art Conventionally, a substrate made of a cemented carbide based on tungsten carbide (hereinafter, referred to as WC) or a cermet based on titanium carbonitride (hereinafter, referred to as TiCN) (hereinafter, these are collectively referred to as a tool substrate) On the surface)
(A) As a lower layer, a carbide layer (hereinafter, referred to as TiC) layer and a nitride layer (hereinafter, also referred to as TiN) layer of Ti formed by chemical vapor deposition and / or physical vapor deposition (hereinafter, simply referred to as vapor deposition). , Carbonitride (hereinafter referred to as TiCN)
Layer, a carbonate (hereinafter referred to as TiCO) layer, and a stack of two or more layers of a carbonitride (hereinafter referred to as TiCNO) layer, and has an average layer thickness of 3 to 20 μm. (B) as an upper layer;
A coated cermet formed by vapor deposition of an aluminum oxide (hereinafter, referred to as Al ₂ O ₃ ) layer having an average layer thickness of 5 to 17 μm and a hard coating layer composed of the above (a) and (b). Tools are known, and it is also known that this coated cermet tool is used for continuous cutting or interrupted cutting of, for example, various kinds of steel or cast iron.

In general, a Ti compound layer and Al ₂ O ₃ constituting a hard coating layer of the above-mentioned coated cermet tool are generally used.
It is also well known that the layer has a granular crystal structure, and the Al ₂ O ₃ layer is widely and practically used, for example, those having an α-type crystal structure or those having a κ-type crystal structure. As described in JP-A-6-8010 and JP-A-7-328808, a TiCN layer constituting the Ti compound layer is formed by a normal chemical vapor deposition apparatus for the purpose of improving the toughness of the layer itself. It is also known that a mixed gas containing an organic carbonitride is used as a reaction gas and formed by chemical vapor deposition at a medium temperature range of 700 to 950 ° C. to have a vertically elongated crystal structure.

[0004]

In recent years, the performance of cutting equipment has been remarkably improved, but on the other hand, there has been a strong demand for labor saving, energy saving, and further cost reduction in cutting work. In the above-mentioned conventional coated cermet tool, there is no problem when it is used for continuous cutting or interrupted cutting under normal conditions such as steel or cast iron. When used for severe high-speed interrupted cutting, that is, high-speed interrupted cutting in which a thermal shock is repeatedly applied to the cutting edge at an extremely short pitch, the Al ₂ O ₃ layer constituting the upper layer of the hard coating layer is hard and heat resistant. Although excellent, it is brittle to thermal shock, so that the hard coating layer is liable to cause chipping (small chipping), and as a result, the service life is relatively short.

[0005]

Means for Solving the Problems Accordingly, the present inventors have
From the above-mentioned viewpoints, as a result of conducting research to improve the thermal shock resistance of the Al ₂ O ₃ layer constituting the upper layer of the hard coating layer of the above-mentioned coated cermet tool, the lower layer was first used under normal conditions. Then, a relatively thick Al ₂ O ₃ layer having a κ-type crystal structure is formed by vapor deposition and subjected to a heat transformation treatment, preferably a heat transformation in an Ar atmosphere at a temperature of 1000 ° C. or more for a predetermined time. When the crystal structure is changed to the α-type by performing the treatment, the transformed cracks are uniformly dispersed and distributed in the transformed α-type Al ₂ O ₃ layer, and then the transformed α-type Al ₂ O _{3 in} this state is obtained. On the surface of the layer, a composite double α-type Al ₂ O ₃ layer formed by vapor-depositing a relatively thin α-type Al ₂ O ₃ layer as an upper layer under the same conditions as the upper layer is coated with a hard cermet tool. When composed as an upper layer of the coating layer together with a Ti compound layer as a lower layer, In the results hard layer of formed comprising coated cermet tool, transformation cracks dispersed uniformly distributed metamorphosis α type the Al ₂ O ₃ layer which constitutes the upper layer, severe especially during high-speed intermittent cutting heat The research result obtained that the occurrence of chipping in the hard coating layer is remarkably suppressed by absorbing and relaxing the impact is obtained.

The present invention has been made on the basis of the above research results, and (a) is formed by vapor deposition as a lower layer on the surface of a tool base made of a WC-based cemented carbide or a TiCN-based cermet. TiC layer, TiN layer, TiC
An N layer, a TiCO layer, and a TiCNO layer, a Ti compound layer having an average layer thickness of 3 to 20 μm, and a lower layer as an upper layer; Al ₂ O ₃ having a κ-type crystal structure
The layer is subjected to a heat transformation treatment to form an α-type crystal structure, a transformed α-type Al ₂ O having a structure in which transformation cracks generated by the heat transformation treatment are uniformly dispersed and distributed, and having an average layer thickness of 3 to 15 μm. _Three layers, the upper layer of which has an average layer thickness of 0.5 to 2 μm.
a composite double α-type Al ₂ O ₃ layer composed of l ₂ O ₃ layers,
And a hard coating layer composed of (b) is formed,
The present invention is characterized by a coated cermet tool having a hard coating layer having excellent thermal shock resistance.

The reason why the average 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) Ti compound layer as a lower layer The Ti compound layer itself has toughness (strength), and the hard coating layer has toughness due to the presence of the Ti compound layer. Transformed α-type Al ₂ O ₃ layer
The layer firmly adheres to any of the layers, and thus has an effect of contributing to the improvement of the adhesion of the hard coating layer to the tool base.However, when the average layer thickness is less than 3 μm, the effect cannot be sufficiently exerted, On the other hand, if the average layer thickness exceeds 20 μm, it becomes easy to cause thermoplastic deformation especially in high-speed interrupted cutting accompanied by high heat generation, which causes uneven wear. Therefore, the average layer thickness is set to 3 to 20 μm. Was.

(B) Transformed α-type Al which is a lower layer of the upper layer
₂ O ₃ layer The transformed α-type Al ₂ O ₃ layer exists under the vapor deposited α-type Al ₂ O ₃ layer, which is the upper layer as described above, and heat is generated by the action of transformation cracks that are uniformly dispersed and distributed in the layer. It has the effect of absorbing impact and preventing chipping from occurring in the hard coating layer,
If the average layer thickness is less than 3 μm, the above effect cannot be sufficiently exerted. On the other hand, if the average layer thickness exceeds 15 μm, the effect of suppressing chipping is sharply reduced, and rather the chipping is accelerated. Therefore, the average layer thickness was determined to be 3 to 15 μm.

(C) Evaporated α-type Al as an upper layer of the upper layer
₂ O ₃ layer The deposited α-type Al ₂ O ₃ layer protects the transformed α-type Al ₂ O ₃ layer, which is likely to be chipped due to transformation cracks in the layer when exposed and present on the above surface, In the state where the transformation crack is incorporated in the hard coating layer, there is an effect of improving abrasion resistance without causing chipping. However, when the average layer thickness is less than 0.5 μm, the effect is sufficiently exerted. On the other hand, if the average layer thickness exceeds 2 μm and becomes too thick, chipping tends to occur in itself, so the average layer thickness is set to 0.5 to 2 μm.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the coated cermet tool of the present invention will be specifically described with reference to examples. As the raw material powder, WC powder, (Ti, W) C (the same hereinafter, TiC / WC = 30/70 by mass ratio) powder having a predetermined average particle size in the range of 0.5 to 4 μm, and ( Ti, W) C
N (TiC / TiN / WC = 24/20/56) powder,
(Ta, Nb) C (TaC / NbC = 90/10) powder, Cr ₃ C ₂ powder, and Co powder were prepared, and these raw material powders were blended into the blending composition shown in Table 1 and wet-processed in a ball mill for 72 hours. After mixing and drying, the mixture is pressed into a green compact having a predetermined shape at a pressure of 98 MPa.
a. Vacuum sintering is performed at 1410 ° C. for 1 hour in the vacuum of a. After sintering, the cutting edge is subjected to a honing process of R: 0.03 mm to form a throw-away tip shape specified in ISO • CNMG120408. Tool bases A to F made of WC-based cemented carbide were prepared.

In addition, as raw material powders,
TiCN having an average particle size of 2 μm (TiC /
(TiN = 50/50) powder, Mo ₂ C powder, ZrC powder, NbC powder, TaC powder, WC powder, Co powder, and Ni powder were prepared, and these raw material powders were blended into the composition shown in Table 2. After wet-mixing with a ball mill for 24 hours and drying, the mixture is pressed into a green compact at a pressure of 98 MPa, and the green compact is fired in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour. After sintering and sintering,
Honing processing of R: 0.03 mm was performed on the cutting edge portions to form tool bases a to f made of TiCN-based cermet having a chip shape of ISO standard, CNMG120412.

Next, the surface of each of the tool bases A to F and the tool bases a to f was measured using a conventional chemical vapor deposition apparatus, and Table 3 (l-TiCN in Table 3 is described in JP-A-6-8010. Under the conditions shown in Table 4 under the conditions shown in Table 4 under the conditions shown in Table 4 below. A thick Ti compound layer was formed by vapor deposition as a lower layer of the hard coating layer, and then an Al ₂ O ₃ layer having a κ-type crystal structure was formed by vapor deposition under the same conditions as shown in Table 3, and the layer was formed in an Ar atmosphere at a temperature : Subjected to a heat transformation treatment at 1050 ° C. for a predetermined time within a range of 2 to 6 hours,
Α-type Al ₂ O ₃ layer in which the transformation cracks are uniformly dispersed and distributed in the layer by transforming the crystal structure of the
Is formed as the lower layer constituting the upper layer of the hard coating layer with the target layer thickness shown in Table 3, and further, under the conditions shown in Table 3 and the target layer thickness shown in Table 4, the deposited α-type Al ₂ O ₃ layer Was formed as a lower layer constituting the upper layer, thereby producing coated cermet tools 1 to 12 of the present invention. Further, for comparison purposes, as shown in Table 5, the conventional coating was carried out under the same conditions except that the entire upper layer of the hard coating layer was a vapor-deposited α-type Al ₂ O ₃ layer having an average layer thickness also shown in Table 5. Cermet tools 1 to 12 were manufactured respectively.

The coated cermet tools 1 to 12 of the present invention and the conventional coated cermet tools 1 to 1
With respect to No. 2, when the constituent layer of the hard coating layer was observed using a scanning electron microscope (observation of the longitudinal section of the layer), in the former, the Ti compound layer and the transformation cracks were uniformly dispersed and distributed in the layer. It consisted of a transformed α-type Al ₂ O ₃ layer and a vapor-deposited α-type Al ₂ O ₃ layer. In the latter case, it was confirmed that both consisted of a Ti compound and a vapor-deposited α-type Al ₂ O ₃ layer. Also,
When the thicknesses of the constituent layers of the hard coating layer of these coated cermet tools were measured using a scanning electron microscope (also in the longitudinal section), the average layer thickness was substantially the same as the target layer thickness (5 points). (Mean value of measurement).

Next, the coated cermet tools 1 to 6 according to the present invention and the conventional coated cermet tools 1 to 6 were screwed to the tip of a tool steel tool with a fixing jig. For No. 6, Work material: JIS SCM440 Lengthwise equally spaced round bar with four longitudinal grooves, Cutting speed: 250 m / min, Cutting depth: 1.5 mm, Feed: 0.3 mm / rev, Cutting time: 5 Dry high-speed intermittent cutting test of alloy steel under the following conditions: Work material: JIS SUS304, longitudinally spaced round bar with four longitudinal grooves, Cutting speed: 150 m / min, Cutting depth: 1.5 mm, Feed : 0.3 mm / rev, cutting time: 5 minutes, and a dry high-speed interrupted cutting test of stainless steel was performed.

Furthermore, the coated cermet tools 7-1 of the present invention
2 and the conventional coated cermet tools 7 to 12 are as follows: Work material: JIS SCM440, a longitudinally spaced round bar with four longitudinal grooves, cutting speed: 250 m / min, depth of cut: 1.5 mm, feed: 0. 3 mm / rev, cutting time: 5 min, dry high-speed intermittent cutting test of alloy steel under the following conditions: Work material: JIS SUS304, 4 longitudinally-spaced round bars at equal intervals in the longitudinal direction, Cutting speed: 150 m / min , Depth of cut: 1.5 mm, feed: 0.3 mm / rev, cutting time: 5 minutes, dry high-speed intermittent cutting test of stainless steel under the following conditions: In all cutting tests, the flank wear width of the cutting edge was measured. did. Table 6 shows the measurement results.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

[0019]

[Table 4]

[0020]

[Table 5]

[0021]

[Table 6]

[0022]

According to the results shown in Tables 4 to 6, the coated cermet tools 1 to 12 of the present invention are uniformly dispersed in the modified α-type Al ₂ O ₃ layer constituting the lower layer of the upper layer of the hard coating layer. Due to the action of the transformation cracks distributed, the thermal shock is extremely high, and even in high-speed interrupted cutting of steel accompanied by high heat generation, the action of the transformation cracks existing in a state embedded in the hard coating layer, the cutting edge portion In the conventional coated cermet tools 1 to 12 in which the entire upper layer of the hard coating layer is formed of a vapor-deposited α-type Al ₂ O ₃ layer, the high-speed For intermittent cutting, the deposition α
It is evident that the mold Al ₂ O ₃ layer cannot withstand severe thermal shock, chipping occurs at the cutting edge, and reaches a service life in a relatively short time. 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 of various steels and cast irons, but also for cutting conditions accompanied by extremely high thermal shock and high heat generation. The cutting performance is excellent even in the severest high-speed intermittent cutting, and therefore, it is possible to satisfactorily cope with the high performance of the cutting device, the labor saving and energy saving of the cutting work, and the cost reduction.

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Claims (1)

[Claims] 1. A tool base comprising a tungsten carbide-based cemented carbide or a titanium carbonitride-based cermet,
(A) as a lower layer, a titanium carbide layer formed by vapor deposition;
A laminate of one or more of a nitride layer, a carbonitride layer, a carbonate layer, and a carbonitride layer;
A Ti compound layer having an average layer thickness of ２０20 μm; (b) an upper layer formed by heating and transforming an aluminum oxide layer having a κ-type crystal structure in a state in which a lower layer is formed by vapor deposition to obtain α.
Having a structure in which transformation cracks generated by the heat transformation treatment are uniformly dispersed and distributed, and 3 to 15 μm.
a modified α-type aluminum oxide layer having an average layer thickness of m, an upper layer of which is composed of a vapor-deposited α-type aluminum oxide layer having an average layer thickness of 0.5 to 2 μm and having an α-type crystal structure formed by vapor deposition. α-type aluminum oxide layer, above (a)
And a hard coating layer formed of (b), wherein the hard coating layer has excellent thermal shock resistance and is made of a surface-coated cermet cutting tool.