JP2006297519A - Surface coated cermet cutting tool having hard coating layer exhibiting excellent chipping resistance in high-speed heavy cutting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface coated cermet cutting tool having a hard coating layer exhibiting excellent chipping resistance in high-speed heavy cutting. <P>SOLUTION: The hard coating layer of the surface coated cermet cutting tool is composed of a lower layer and an upper layer, wherein (a) the lower layer is Ti compound layer which is composed of one or more layers of TiC layer, TiN layer, TiCN layer, TiCO layer and TiCNO layer each formed by chemical deposition, and a reformed TiCN layer which has an average layer thickness of 2.5 to 15 μm, satisfies a formula (Ti<SB>1-X</SB>Cr<SB>X</SB>)C<SB>1-Y</SB>N<SB>Y</SB>, (where X is 0.005 to 0.05, Y is 0.45 to 0.55 by atomic ratio.) and indicates a specific constituent atom sharing lattice point distribution graph, and has total average layer thickness of 3 to 20 μm, and (b) the abovementioned upper layer is Al<SB>2</SB>O<SB>3</SB>layer which has an average layer thickness of 1 to 15 μm and α-type crystal structure in a state formed by chemical vapor deposition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface-coated cermet cutting tool (hereinafter referred to as a coated cermet tool) that exhibits excellent chipping resistance with a hard coating layer, particularly in high-speed heavy cutting of steel or cast iron.

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) Ti carbide (hereinafter referred to as TiC) layer, nitride (hereinafter also referred to as TiN) layer, carbonitride (hereinafter referred to as TiCN) layer formed by chemical vapor deposition of the lower layers. A Ti compound layer consisting of two or more of a carbon oxide (hereinafter referred to as TiCO) layer and a carbonitride oxide (hereinafter referred to as TiCNO) layer and having a total average layer thickness of 3 to 20 μm,
(B) an upper layer having an average layer thickness of 1 to 15 μm, and an aluminum oxide (hereinafter referred to as Al ₂ O ₃ ) layer having an α-type crystal structure in a state of chemical vapor deposition;
A coated cermet tool formed by forming a hard coating layer composed of (a) and (b) above is known, and this coated cermet tool is used for continuous cutting and intermittent cutting of various steels and cast irons, for example. It is also known that
Japanese Unexamined Patent Publication No. 6-31503

In recent years, the performance of cutting equipment has been remarkable, while there is a strong demand for labor saving and energy saving and further cost reduction for cutting, and with this, cutting speed has been increased for the purpose of improving cutting efficiency, and Cutting tends to be performed under high-speed heavy cutting conditions that increase cutting depth and feed, etc., but the above-mentioned conventional coated cermet tools can be used for continuous cutting and intermittent cutting under normal conditions such as steel and cast iron. There is no problem when it is used, but when it is used for high-speed heavy cutting with severe cutting conditions, that is, when it is used for high-speed heavy cutting where a very high mechanical load is applied to the cutting edge, the hard coating layer constituting this the high-temperature strength by Ti compound layer of the lower layer, although provided with a high-temperature hardness and heat resistance by the Al ₂ O ₃ layer of the upper layer, is insufficient high-temperature strength by the Ti compound layer For this reason, the mechanical high load cannot be satisfied satisfactorily, and as a result, the hard coating layer is likely to be chipped (small chipping), so that the service life is reached in a relatively short time. is the current situation.

In view of the above, the present inventors, from the above viewpoint, in order to improve the chipping resistance of the hard coating layer of the above-mentioned coated cermet tool, the TiCN layer constituting the Ti compound layer, which is the lower layer thereof, that is, Ti The compound layer has a relatively high high-temperature strength and, as shown in the schematic diagram of FIG. 2A, the constituent atoms composed of Ti, carbon (C), and nitrogen (N) are respectively present at the lattice points. As a result of conducting research by focusing on a TiCN layer having an existing NaCl-type face-centered cubic crystal structure (note that FIG. 2 (b) shows a state cut by the (011) plane),
(A) In the hard coating layer of the conventional coated cermet tool, the TiCN layer of the Ti compound layer constituting the lower layer is, for example, an ordinary chemical vapor deposition apparatus.
Reaction gas composition: by _{volume%, TiCl 4: 2~10%,} CH 3 CN: 0.5~3%, N 2: 10~30%, H 2: remainder,
Reaction atmosphere temperature: 800 to 900 ° C.
Reaction atmosphere pressure: 6-20 kPa,
It is formed by vapor deposition under the conditions (called normal conditions)
Reaction gas composition: by _{volume%, TiCl 4: 2~10%,} CrCl 3: 0.01~0.5%, CH 3 CN: 1~4%, N 2: 20~40%, H 2: remainder,
Reaction atmosphere temperature: 800 to 900 ° C.
Reaction atmosphere pressure: 6-20 kPa,
Under the above conditions, that is, the reaction gas in the above normal conditions with a very small amount of CrCl ₃ gas added,
Composition formula: (Ti _1-X Cr _X ) C _1-Y N _Y (however, in atomic ratio, X: 0.005-0.05, Y: 0.45-0.55),
When the Ti-based carbonitride layer satisfying the above is formed, the resulting Ti-based carbonitride layer (hereinafter referred to as “modified Ti-based CN layer”) has the same crystal structure as the TiCN layer shown in FIG. Structure, that is, a crystal structure of NaCl-type face-centered cubic crystals in which constituent atoms composed of Ti, Cr, carbon (C), and nitrogen (N) are present at lattice points, as schematically shown in FIG. (In addition, FIG.1 (b) shows the state cut | disconnected by the (011) plane).

(B) About the TiCN layer (hereinafter referred to as “conventional TiCN layer”) constituting the lower layer of the hard coating layer of the conventional coated cermet tool and the modified Ti-based CN layer of (a) above,
Using a field emission scanning electron microscope, as illustrated in the schematic explanatory diagrams in FIGS. 2A and 2B, each crystal grain existing within the measurement range of the surface polished surface is irradiated with an electron beam, The inclination angle formed by the normal lines of the (001) plane and the (011) plane, which are crystal planes of the crystal grains, with respect to the normal line of the surface polished surface (FIG. 3A shows (001) of the crystal planes). When the tilt angle of the surface is 0 degree and the tilt angle of the (011) plane is 45 degrees, the tilt angle of the (001) plane is 45 degrees and the tilt angle of the (011) plane is 0 degree. In this case, the crystal grains are measured at lattice points as described above, and in the conventional TiCN layer, Ti, carbon (C ), Nitrogen (N), and the modified Ti-based CN layer is composed of Ti, Cr, carbon (C), and nitrogen (N) Each of the constituent atoms has an interfacial crystal structure at the interface between adjacent crystal grains based on the measured tilt angle. The distribution of lattice points that share one constituent atom between them (constituent atom shared lattice points) is calculated, and N lattice points that do not share constituent atoms between the constituent atom shared lattice points (N is a NaCl-type face-centered cubic) The distribution of constitutive atomic shared lattice points is expressed as ΣN + 1, and the distribution ratio of each ΣN + 1 to the entire ΣN + 1 (however, the upper limit is 28 due to the frequency) When the constituent atomic share lattice distribution graph shown is created, the highest peak exists in Σ3 in both the modified Ti-based CN layer and the conventional TiCN layer, but the conventional TiCN layer is illustrated in FIG. Street, Σ3 In contrast to the relatively low constituent atom shared lattice point distribution graph with a distribution ratio of 30% or less, the modified Ti-based CN layer has a Σ3 distribution ratio of 60% or more as illustrated in FIG. 2 shows a distribution graph of extremely high constituent atomic shared lattice points, and the distribution ratio of this high Σ3 is changed by adjusting the content ratio of Cr in the modified Ti-based CN layer.

(C) When forming the modified Ti-based CN layer, the atomic ratio of the Cr content in the layer is 0.005 to 0.5 in terms of the atomic ratio to the total amount with Ti as described above, thereby sharing the constituent atoms The distribution ratio of Σ3 in the lattice point distribution graph becomes extremely high of 60% or more, and as a result, the layer has a further improved high-temperature strength as compared with the conventional TiCN layer. Even if the Cr content ratio deviates from the lower range or the higher range, the distribution ratio of Σ3 in the constituent atom shared lattice point distribution graph becomes less than 60%, and the desired high temperature strength is improved. The effect cannot be obtained.

(D) A coated cermet in which the upper layer of the hard coating layer is composed of the Al ₂ O ₃ layer, the lower layer is composed of the Ti compound layer, and one of the Ti compound layers is composed of the modified Ti-based CN layer. In the tool, since the modified Ti-based CN layer has a higher high-temperature strength than the conventional TiCN layer, the high-temperature hardness and heat resistance provided by the Al ₂ O ₃ layer as the upper layer are compatible. In other words, the hard coating layer exhibits excellent chipping resistance even in high-speed heavy cutting with extremely high load, and exhibits excellent wear resistance over a long period of time.
The research results shown in (a) to (c) above were obtained.

The present invention has been made based on the above research results, and on the surface of a tool base composed of a WC-based cemented carbide or TiCN-based cermet,
(A) One or more of the TiC layer, TiN layer, TiCN layer, TiCO layer, and TiCNO layer formed by chemical vapor deposition of the lower layer, and an average layer thickness of 2.5 to 15 μm And having
While satisfying the composition formula: (Ti _1-X Cr _X ) C _1-Y N _Y (wherein, X: 0.005 to 0.05, Y: 0.45 to 0.55 in atomic ratio)
Using a field emission scanning electron microscope, each crystal grain existing within the measurement range of the surface polished surface is irradiated with an electron beam, and the crystal plane of the crystal grain is normal to the surface polished surface ( The inclination angle formed by the normal lines of the (001) plane and the (011) plane is measured. In this case, the crystal grains are NaCl-type face-centered cubes in which constituent atoms composed of Ti, Cr, carbon, and nitrogen exist at lattice points. A lattice in which each of the constituent atoms shares one constituent atom between the crystal grains at the interface between adjacent crystal grains based on the measured tilt angle obtained as a result of the crystal structure The distribution of the points (constituent atom shared lattice points) is calculated, and there are N lattice points that do not share the constituent atoms between the constituent atom shared lattice points (N is an even number of 2 or more in the crystal structure of the NaCl type face centered cubic crystal). ΣN is the existing configuration of atomic atom lattice points. In the constituent atom sharing lattice distribution graph showing the distribution ratio of each ΣN + 1 in the entire ΣN + 1 (however, the upper limit is 28 due to the frequency), the highest peak exists in Σ3, A modified Ti-based CN layer showing a constituent atom shared lattice point distribution graph in which the distribution ratio of Σ3 to the entire ΣN + 1 is 60% or more;
And a Ti compound layer having a total average layer thickness of 3 to 20 μm,
(B) The upper layer has an average layer thickness of 1 to 15 μm, and an Al ₂ O ₃ layer having an α-type crystal structure in the state of chemical vapor deposition,
The present invention is characterized by a coated cermet tool that forms the hard coating layer constituted by (a) and (b) and exhibits excellent chipping resistance in high-speed heavy cutting.

Next, the reason why the constituent layers of the hard coating layer of the coated cermet tool of the present invention are numerically limited as described above will be described below.
(A) Ti compound layer (lower layer)
The Ti compound layer itself has high-temperature strength, and the presence of the Ti compound layer makes the hard coating layer have high-temperature strength, and firmly adheres to both the tool base and the upper Al ₂ O ₃ layer. Therefore, it has an effect of improving the adhesion of the hard coating layer to the tool base, but if the total average layer thickness is less than 3 μm, the above-mentioned effect cannot be sufficiently exhibited, while the total average layer thickness is If it exceeds 20 μm, it becomes easy to cause thermoplastic deformation particularly by high-speed intermittent cutting accompanied by generation of high heat, which causes uneven wear. Therefore, the total average layer thickness is set to 3 to 20 μm.

(B) Modified Ti-based CN layer (lower layer)
The distribution ratio of Σ3 in the constituent atomic share lattice point distribution graph of the modified Ti-based CN layer is the atomic ratio of the Cr content ratio (X value) in the layer to the total amount with Ti as described above. Although it can be set to 60% or more by setting 005 to 0.5, even if the content ratio is less than 0.005 or more than 0.05, the distribution ratio of Σ3 is less than 60%, In high-speed heavy cutting, the hard coating layer does not cause chipping and an excellent effect of improving high-temperature strength cannot be secured. Therefore, the higher the distribution ratio of Σ3, the better, but in this case the distribution ratio of Σ3 is 80 It is difficult for the layer formation to be higher than%.
In addition, the C component in the modified Ti-based CN layer improves the hardness of the layer, while the N component has the effect of improving the strength. By coexisting these two components, high hardness and excellent strength can be obtained. Therefore, if the content ratio (Y value) of the N component in the layer is less than 0.45 in terms of the atomic ratio to the total amount with the C component, the desired strength cannot be secured. On the other hand, if the content ratio (Y value) similarly exceeds 0.55, the content ratio of the C component becomes relatively small and the desired high hardness cannot be obtained. .45 to 0.55.
As described above, the modified Ti-based CN layer has higher temperature strength than the conventional TiCN layer as described above. However, if the average layer thickness is less than 2.5 μm, the desired excellent high temperature is obtained. The hard coating layer cannot be sufficiently provided with the effect of improving the strength. On the other hand, if the average layer thickness exceeds 15 μm, the thermoplastic deformation that causes uneven wear tends to occur, and wear is accelerated. Therefore, the average layer thickness was determined to be 2.5 to 15 μm.

(C) Al ₂ O ₃ layer (upper layer)
The Al ₂ O ₃ layer has excellent high-temperature hardness and heat resistance, and contributes to improving the wear resistance of the hard coating layer. However, if the average layer thickness is less than 1 μm, the hard coating layer has sufficient wear resistance. On the other hand, if the average layer thickness exceeds 15 μm and becomes too thick, chipping tends to occur. Therefore, the average layer thickness is set to 1 to 15 μm.

  In addition, for the purpose of identification before and after the use of the cutting tool, the TiN layer having a golden color tone may be vapor-deposited as necessary, but the average layer thickness in this case is 0.1 to 1 μm may be sufficient, and 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 for an average layer thickness of up to 1 μm.

  The coated cermet tool according to the present invention has a modified Ti-based CN layer, which is one of the Ti compound layers as the lower layer of the hard coating layer, even in high-speed heavy cutting such as steel and cast iron with extremely high mechanical load. Since it has excellent high-temperature strength and exhibits excellent chipping resistance, the hard coating layer exhibits excellent wear resistance without occurrence of chipping.

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

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 was R: 0.07 mm honing By performing the processing, tool bases A to F made of a WC-base cemented carbide having a throwaway tip shape defined in ISO · CNMG12041 were manufactured.

Further, as raw material powders, TiCN (mass ratio, TiC / TiN = 50/50) powder, Mo ₂ C powder, ZrC powder, NbC powder, TaC powder, WC, all having an average particle diameter of 0.5 to 2 μm. Prepare powder, Co powder, and Ni powder, blend these raw material powders into the composition shown in Table 2, wet mix with a ball mill for 24 hours, dry, and press-mold into a green compact at 98 MPa pressure The green compact is sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour, and after sintering, the cutting edge portion is subjected to a honing process of R: 0.07 mm. Tool bases a to f made of TiCN-based cermet having a chip shape conforming to ISO standards / CNMG 120212 were formed.

Next, a Ti compound layer including a modified Ti-based CN layer is formed as a lower layer of the hard coating layer on the surface of the tool bases A to F and the tool bases a to f using a normal chemical vapor deposition apparatus. In the conditions shown in Table 4, vapor deposition is performed with the combinations and target layer thicknesses shown in Table 4, and then the Al ₂ O ₃ layer as the upper layer is also used in the combinations shown in Table 4 under the conditions shown in Table 3 And this invention covering cermet tool 1-13 was manufactured by carrying out vapor deposition formation with target layer thickness, respectively.

For comparison purposes, as a lower layer of the hard coating layer, a Ti compound layer including a conventional TiCN layer is vapor-deposited with the combinations and target layer thicknesses shown in Table 5 under the conditions shown in Table 3, and the upper layer. Conventionally coated cermet tools 1 to 13 were manufactured by depositing the Al ₂ O ₃ layer under the conditions shown in Table 3 and with the target layer thicknesses shown in Table 5, respectively.

Next, with respect to the modified Ti-based CN layer and the conventional TiCN layer constituting the hard coating layer of the above-described coated cermet tool of the present invention and the conventional coated cermet tool, a constituent atomic shared lattice point distribution graph is obtained using a field emission scanning electron microscope. Was created respectively.
That is, the constituent atomic shared lattice point distribution graph is set in a lens barrel of a field emission scanning electron microscope in a state where the surfaces of the modified Ti-based CN layer and the conventional TiCN layer are polished surfaces. An electron backscatter diffraction image apparatus is used by irradiating an electron beam with an acceleration voltage of 15 kV on a surface with an irradiation current of 15 kV with an irradiation current of 1 nA and on each crystal grain existing in the measurement range of the surface polished surface. Inclination angles formed by the normal lines of the (001) plane and the (011) plane, which are crystal planes of the crystal grains, with respect to the normal line of the surface-polished surface in a 30 × 50 μm region at an interval of 0.1 μm / step Based on the measurement inclination angle obtained as a result of this, lattice points (constituent atoms) in which each of the constituent atoms shares one constituent atom between the crystal grains at the interface between adjacent crystal grains are measured. Share grid point) distribution, The constitutive atomic shared lattice point form is expressed by ΣN + 1 where there are N lattice points that do not share the constituent atoms between the constituent atomic shared lattice points (N is an even number of 2 or more in the crystal structure of the NaCl type face centered cubic crystal). In this case, each ΣN + 1 is created by determining the distribution ratio of ΣN + 1 in the entire ΣN + 1 (however, the upper limit value is 28 in relation to the frequency).

  In the resulting modified Ti-based CN layer and the conventional TiCN shared lattice point distribution graph of TiCN, the distribution ratio of Σ3 in the entire ΣN + 1 (N is all even numbers in the range of 2 to 28) The results are shown in Tables 4 and 5, respectively.

In each of the above-mentioned various constituent atomic share lattice point distribution graphs, as shown in Tables 4 and 5, each of the modified Ti-based CN layers of the coated cermet tool of the present invention has a distribution ratio of Σ3 of 60% or more. While the constituent atom sharing lattice point distribution graph is shown, the conventional TiCN layer of the conventional coated cermet tool shows a constituent atom sharing lattice point distribution graph in which the distribution ratio of Σ3 is 30% or less.
4 is a constituent atomic shared lattice point distribution graph of the modified Ti-based CN layer of the coated cermet tool 3 of the present invention, and FIG. 4 is a constituent atomic shared lattice point distribution graph of the conventional TiCN layer of the conventional coated cermet tool 5. Each is shown.

Further, for the above-described coated cermet tools 1 to 13 and the conventional coated cermet tools 1 to 13, the constituent layers of the hard coating layer were observed using an electron beam microanalyzer (EPMA) and an Auger spectroscopic analysis device (layer When the longitudinal section was observed), it was confirmed that both the former and the latter were composed of a Ti compound layer and an Al ₂ O ₃ layer having substantially the same composition as the target composition. Moreover, when the thickness of the constituent layer of the hard coating layer of these coated cermet tools was measured using a scanning electron microscope (same longitudinal section measurement), the average layer thickness (substantially the same as the target layer thickness) Average value of 5-point measurement) was shown.

Next, with the various coated cermet tools described above, the present coated cermet tools 1 to 13 and the conventional coated cermet tools 1 to 13 in the state where all the above-mentioned various coated cermet tools are screwed to the tip of the tool steel tool with a fixing jig.
Work material: JIS / S53C round bar,
Cutting speed: 450 m / min,
Cutting depth: 5mm,
Feed: 0.25mm / rev,
Cutting time: 8 minutes
Wet continuous high-speed high-cut cutting test of carbon steel under the above conditions (cutting condition A) (normal cutting speed and cutting amount are 200 m / min and 1.5 mm, respectively),
Work material: JIS / FCD500 lengthwise equidistant 4 bars with vertical grooves,
Cutting speed: 350 m / min,
Incision: 1.5mm,
Feed: 0.5mm / rev,
Cutting time: 8 minutes
Wet intermittent high-speed high-feed cutting test of ductile cast iron under the following conditions (cutting condition B) (normal cutting speed and feed are 200 m / min and 0.3 mm / rev),
Work material: JIS / SNCM625 lengthwise equally spaced 4 rods with vertical grooves,
Cutting speed: 380 m / min,
Cutting depth: 4.5mm,
Feed: 0.3mm / rev,
Cutting time: 8 minutes
Wet intermittent high-speed high-cut cutting test (normal cutting speed and cutting depth are 180 m / min and 1.5 mm, respectively) of alloy steel under the above conditions (cutting condition C), and any cutting test (water-soluble cutting oil) Use), the flank wear width of the cutting edge was also measured. The measurement results are shown in Table 6.

  From the results shown in Tables 4 to 6, the coated cermet tools 1 to 13 of the present invention each have a structure in which one of the Ti compound layers as the lower layer of the hard coating layer has a distribution ratio of Σ3 of 60% or more. It is composed of a modified Ti-based CN layer showing an atomic shared lattice point distribution graph, and even in high-speed heavy cutting of steel and cast iron with extremely high mechanical load, the modified Ti-based CN layer has a higher temperature strength that is even better. One of the Ti compound layers, which is the lower layer of the hard coating layer, exhibits excellent chipping resistance, so that the occurrence of chipping in the hard coating layer is remarkably suppressed and exhibits excellent wear resistance. However, in the conventional coated cermet tools 1 to 13 composed of the conventional TiCN layer showing the constituent atomic shared lattice point distribution graph in which the distribution ratio of Σ3 is 30% or less, all of the high-temperature heavy cutting lacks the high-temperature strength of the hard coating layer. Gahara For this reason, it is apparent that chipping occurs in the hard coating layer and the service life is reached in a relatively short time.

  As described above, the coated cermet tool of the present invention has a hard coating layer not only for continuous cutting and interrupted cutting under normal conditions such as various steels and cast iron, but also for high-speed heavy cutting that requires particularly high high-temperature strength. Since it exhibits excellent chipping resistance and exhibits excellent cutting performance over a long period of time, it is fully satisfactory for higher performance of cutting equipment, labor saving and energy saving of cutting, and cost reduction. It can be done.

It is a schematic diagram which shows the crystal structure of the NaCl type face centered cubic crystal which the modified Ti type | system | group CN layer which comprises the Ti compound layer which is a lower layer of a hard coating layer has. It is a schematic diagram which shows the crystal structure of the NaCl type face centered cubic crystal which the conventional TiCN layer which comprises the Ti compound layer which is a lower layer of a hard coating layer has. It is a schematic explanatory drawing which shows the measurement aspect of the inclination angle of the (001) plane of a crystal grain and the (011) plane in the modified Ti type | system | group CN layer which comprises the Ti compound layer which is a lower layer of a hard coating layer, and the conventional TiCN layer. . 4 is a constituent atomic shared lattice distribution graph of a modified TiCN layer constituting a Ti compound layer that is a lower layer of a hard coating layer of the coated cermet tool 3 of the present invention. 4 is a constituent atomic share lattice point distribution graph of a conventional TiCN layer constituting a Ti compound layer that is a lower layer of a hard coating layer of a conventional coated cermet tool 5.

Claims (1)

On the surface of the tool base composed of tungsten carbide based cemented carbide or titanium carbonitride based cermet,
(A) one or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, and carbonitride layer formed by chemical vapor deposition, Having an average layer thickness of 2.5 to 15 μm, and
Composition formula: (Ti _1-X Cr _X ) C _1-Y N _Y (however, in atomic ratio, X: 0.005-0.05, Y: 0.45-0.55),
And using a field emission scanning electron microscope, each crystal grain existing within the measurement range of the surface polished surface is irradiated with an electron beam, and the crystal grain The inclination angle formed by the normal lines of the (001) plane and the (011) plane, which are crystal planes, is measured. In this case, the crystal grains are composed of Ti, Cr, carbon (C), and nitrogen (N) at lattice points. Each of the constituent atoms has a crystal structure of an NaCl type face centered cubic crystal in which each constituent atom exists, and at the interface between adjacent crystal grains based on the measurement tilt angle obtained as a result. The distribution of lattice points (constituent atom shared lattice points) that share one constituent atom between each other is calculated, and N lattice points that do not share constituent atoms between the constituent atom shared lattice points (N is a NaCl type face center) (It will be an even number of 2 or more in the cubic crystal structure) When the constituent atomic shared lattice point form is expressed as ΣN + 1, in the constituent atomic shared lattice point distribution graph showing the distribution ratio of each ΣN + 1 in the entire ΣN + 1 (however, the upper limit is 28 in relation to the frequency), A total average of 3 to 20 μm, which is composed of a modified Ti-based carbonitride layer showing a constituent atomic shared lattice point distribution graph in which the highest peak exists and the distribution ratio of the Σ3 to the entire ΣN + 1 is 60% or more A Ti compound layer having a layer thickness,
(B) an upper layer has an average layer thickness of 1 to 15 μm, and an aluminum oxide layer having an α-type crystal structure in the state of chemical vapor deposition;
A surface-coated cermet cutting tool that exhibits excellent chipping resistance in a high-speed heavy cutting process, which is formed by vapor-depositing the hard coating layer composed of (a) and (b) above.

Images