JP2018039081A - Surface-coated cutting tool having hard coating layer exerting excellent chipping resistance and wear resistance - Google Patents

Abstract

Provided is a coated tool in which a hard coating layer has heat cracking resistance and exhibits excellent chipping resistance and wear resistance. A hard coating layer includes at least a TiAlN layer having an average Al content of 0.7 to 0.9 (however, an atomic ratio), and the TiAlN layer includes crystal grains having a columnar structure, And it includes at least crystal grains having a NaCl-type face-centered cubic structure, and further comprises an inner layer portion in contact with the base material or the underlayer and a surface layer portion located on the outer surface, and constitutes the inner layer portion of the TiAlN layer There are pores at the grain boundaries of the crystal grains, the area ratio of the pores in the longitudinal section is 1% or more and less than 20%, the average pore diameter of the pores is 2 to 50 nm, When the diffraction peak intensity Ifcc (111) of the (111) plane and the diffraction peak intensity Ifcc (200) of the (200) plane are obtained, Ifcc (111) / (Ifcc (111) + Ifcc (200) )) ≧ 0.5 is satisfied. [Selection] Figure 1

Description

  The present invention is accompanied by high heat generation such as steel and cast iron, and has high thermal crack resistance with a hard coating layer in wet high-speed cutting processing in which a thermal and mechanical high load acts on the cutting edge. The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits excellent wear resistance over a long period of use without causing abnormal damage such as chipping and chipping.

Conventionally, the surface of a tool base (hereinafter collectively referred to as a tool base) made of tungsten carbide (hereinafter referred to as WC) base cemented carbide or titanium carbonitride (hereinafter referred to as TiCN) base cermet. Furthermore, as hard coating layers, there are known coating tools in which a Ti-Al based composite nitride layer is formed by physical vapor deposition or chemical vapor deposition, and these are known to exhibit excellent wear resistance. It has been.
However, when the Al content is increased in order to increase the hardness of the hard coating layer, AlN having a hexagonal structure is likely to be formed in the Ti—Al based composite nitride layer. There is a problem that the hardness decreases and the life as a cutting tool is shortened by the formation of.

In order to improve such problems, for example, as shown in Patent Document 1, “a base material composed of a WC-based cemented carbide or cermet is composed of one or more layers, At least one layer includes a multilayer structure in which a first unit layer made of TiN and a second unit layer made of Ti _1-x Al _x N are alternately stacked, and the first unit layer has an fcc-type crystal structure. And the second unit layer has an fcc type crystal structure, and X in the Ti _1-x Al _x N is 0.6 or more and 0.9 or less, preferably, the second unit layer is In the X-ray diffraction spectrum, a “coated tool in which a film in which a peak derived from the (111) plane or the (200) plane has the maximum intensity” has been proposed.
Further, as a method for manufacturing the coating film, “a CVD process for forming at least one of the layers using a CVD method is included, and the CVD process includes a first gas containing titanium and aluminum; , A jetting step of jetting a second gas containing nitrogen toward the base material, and a heating condition of 850 ° C. or higher and 1000 ° C. or lower for the base material after the jetting step for a period of 5 minutes to 30 minutes. And a cooling step of cooling the base material after the annealing step at a cooling rate of 7 ° C./min or more ”.
In the coated tool, _{x in} the second unit layer made of Ti _1-x Al _x N can be maintained at a high value of 0.6 or more and 0.9 or less, and hcp in the second unit layer. Since precipitation of -AlN can be suppressed, it is said that a film having high hardness and high oxidation resistance can be provided.

Special table 2015-52133 gazette

In recent years, there has been a strong demand for energy saving and energy saving in cutting, and along with this, cutting tends to be faster and more efficient, and the coated tool has even more chipping resistance, chipping resistance, Abnormal damage resistance such as peel resistance is required, and excellent wear resistance over a long period of use is required.
However, the coated tool described in Patent Document 1 exhibits excellent wear resistance in dry cutting of steel and cast iron, but is wet in which a high thermal and mechanical load acts on the cutting edge. In high-speed cutting, there is a problem that the life is reached early due to occurrence of abnormal damage such as chipping and chipping.
Therefore, there is a need for a coated tool that exhibits excellent wear resistance over a long period of use without causing chipping or chipping in wet high-speed cutting.

  From the above-mentioned viewpoint, the present inventors have found that in a coated tool in which a hard coating layer including at least a composite nitride of Ti and Al (hereinafter sometimes referred to as “TiAlN”) is formed by chemical vapor deposition, chipping and chipping As a result of intensive research on hard coating layers of coated tools that exhibit excellent wear resistance over long-term use without causing abnormal damage such as the following, the following findings were obtained.

  That is, the inventors of the present invention formed a TiAlN layer under limited conditions. First, in a region (inner layer portion) in contact with the base material or the base layer, pores along the grain boundary of the TiAlN layer ( Micro-holes) are formed, functioning as a cushioning material that mitigates the mismatch between the thermal expansion of the coating and the base material due to heat generated during wet cutting, thereby reducing the accumulation of strain due to thermal expansion and preventing thermal cracking and chipping. In addition, in the outermost layer region (surface layer part), an aluminum oxide layer is formed on the coating surface by cutting heat due to the high aluminum content, and this oxide layer acts as a protective film. Therefore, the generation and propagation of cracks in the TiAlN layer can be suppressed, so that the coated tool on which such a TiAlN layer is formed as a hard coating layer is In wet high-speed cutting machining, high load is applied was found to excellent resistance to cracking, chipping resistance exhibited.

  Further, with respect to TiAlN columnar crystal grains having a NaCl-type face-centered cubic structure (hereinafter sometimes simply referred to as “cubic structure”) constituting the TiAlN layer, a diffraction peak intensity is obtained by X-ray diffraction measurement, and (111 ) Plane diffraction peak intensity is Ifcc (111) and (200) plane diffraction peak intensity is Ifcc (200), Ifcc (111) / (Ifcc (111) + Ifcc (200)) ≧ 0.5 It has been found that the wear resistance of the TiAlN layer is improved when the above is satisfied.

  Further, the TiAlN layer was subjected to X-ray diffraction measurement, and the (111) plane diffraction peak intensity Ifcc (111) of the cubic TiAlN crystal grains and the (100) plane diffraction peak intensity Ihcp (6) of the hexagonal TiAlN crystal grains. 100), if Ifcc (111) / (Ifcc (111) + Ihcp (100)) ≧ 0.9, the TiAlN layer is mainly composed of crystal grains having a cubic structure. It was found that the wear resistance was further improved.

The present invention has been made based on the above knowledge,
“(1) In a surface-coated cutting tool in which a hard coating layer is provided on the surface of a tool base composed of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet,
(A) The hard coating layer includes at least a composite nitride layer of Ti and Al having an average layer thickness of 1.5 μm or more and 15 μm or less,
(B) The Ti and Al composite nitride layer is composed of crystal grains having a columnar structure and includes at least crystal grains having a NaCl-type face-centered cubic structure;
(C) The composite nitride layer of Ti and Al has the composition
Composition formula: (Ti _1-x Al _x ) N
The average content ratio X _avg (where X _avg is the atomic ratio) of the total amount of Ti and Al in Al satisfies 0.7 ≦ X _avg ≦ 0.9,
(D) The Ti and Al composite nitride layer is composed of an inner layer portion in contact with the base material or the underlayer and a surface layer portion located on the outer surface,
(E) The film thickness of the inner layer portion is 0.5 μm or more, and pores exist at the grain boundaries of the crystal grains of the inner layer portion, and the area ratio and average occupied by the pores in the longitudinal section of the inner layer portion When the pore diameter is calculated, the area ratio of the pore to the observation area is 5% or more and less than 20%, and the average pore diameter of the pore is 2 nm or more and 50 nm or less,
(F) The film thickness of the surface layer portion is 1.0 μm or more, and when calculating the area ratio and the average pore diameter occupied by the pores in the longitudinal section of the surface layer section, the area ratio occupied by the pores with respect to the observation area area is Less than 0.5% and the average pore diameter of the pores is 50 nm or less,
(G) X-ray diffraction is performed on the crystal grains having the NaCl-type face-centered cubic structure constituting the composite nitride layer of Ti and Al, and the diffraction peak intensity Ifcc (111) on the (111) plane is expressed by (200) A surface-coated cutting tool characterized by satisfying a relationship of Ifcc (111) / (Ifcc (111) + Ifcc (200)) ≧ 0.5 when the diffraction peak intensity Ifcc (200) of the surface is obtained.
(2) The composite nitride layer of Ti and Al is subjected to X-ray diffraction, and has a diffraction peak intensity Ifcc (111) of the (111) plane of a crystal grain having a NaCl type face centered cubic structure and a hexagonal crystal structure. When the diffraction peak intensity Ihcp (100) of the (100) plane of the crystal grain is obtained, the relationship of Ifcc (111) / (Ifcc (111) + Ihcp (100)) ≧ 0.9 is satisfied ( The surface-coated cutting tool according to 1).
(3) One or two of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer and carbonitride layer between the tool base and the composite nitride layer of Ti and Al The surface-coated cutting tool according to (1) or (2), wherein a lower layer comprising at least one Ti compound layer is provided with a total average layer thickness of 0.1 to 20 μm. "
It has the characteristics.

  The present invention will be described in detail below.

Average thickness of the TiAlN layer:
The hard coating layer of the present invention is a composite nitride of Ti and Al (TiAlN) layer represented by the composition formula: (Ti _1-x Al _x ) N (however, the average content in the total amount of Ti and Al in Al) The ratio X _avg (where X _avg is an atomic ratio) satisfies at least 0.70 ≦ X _avg ≦ 0.90).
This TiAlN layer has high hardness and excellent wear resistance, but the effect is particularly remarkable when the average layer thickness is 1.5 μm or more and 15 μm or less.
That is, the TiAlN layer has the inner layer portion and the surface layer portion, but the inner layer portion cannot exhibit excellent thermal crack resistance and chipping resistance when the film thickness is less than 0.5 μm. Since the surface layer portion cannot exhibit excellent wear resistance when the film thickness is less than 1.0 μm, in order to sufficiently ensure wear resistance and heat crack resistance / chipping resistance over a long period of use, The film thickness of the inner layer portion was set to 0.5 μm or more, the film thickness of the surface layer portion was set to 1.0 μm or more, and the average layer thickness of the TiAlN layer was set to 1.5 μm or more.
On the other hand, when the average thickness of the TiAlN layer exceeds 15 μm, the crystal grains of the TiAlN layer are likely to be coarsened and chipping is likely to occur. Therefore, the average layer thickness is set to 15 μm or less.

Columnar structure and crystal structure of TiAlN layer:
Since the TiAlN layer of the present invention is composed of crystal grains having a columnar structure and includes at least crystal grains having a NaCl-type face-centered cubic structure, the TiAlN layer has excellent high hardness, and therefore has excellent wear resistance. Demonstrate sex.

  When the TiAlN crystal grains having the cubic structure of the TiAlN layer of the present invention are obtained by calculating the diffraction peak intensity Ifcc (111) of the (111) plane and the diffraction peak intensity Ifcc (200) of the (200) plane by X-ray diffraction. , Ifcc (111) / (Ifcc (111) + Ifcc (200)) ≧ 0.5, since the (111) orientation of the dense surface is high, the wear resistance of the TiAlN layer is high. Improve dramatically.

Further, the TiAlN layer of the present invention was subjected to X-ray diffraction, and the diffraction peak intensity Ifcc (111) of the (111) plane of the crystal grain having a cubic structure and the diffraction of the (100) plane of the crystal grain having a hexagonal crystal structure When the peak intensity Ihcp (100) is obtained, it is preferable to satisfy the relationship Ifcc (111) / (Ifcc (111) + Ihcp (100)) ≧ 0.9.
In this case, since the TiAlN layer is mainly composed of TiAlN crystal grains having a cubic structure, the wear resistance is further improved.

The TiAlN layer of the present invention is composed of crystal grains having a columnar structure, and the columnar structure will be specifically described below using the aspect ratio of the crystal grains.
That is, for the longitudinal section of the TiAlN layer, when the particle width and particle length of individual crystal grains in the layer are measured and the average particle width W and average particle length L are determined, the average particle width W is 0.1. The effect of improving toughness and wear resistance can be exhibited by constituting a columnar structure in which the average aspect ratio A (= L / W) is 2 to 20 and ˜2 μm.
Here, the reason why the average particle width W is set to 0.1 to 2 μm is that, when the average particle width W is less than 0.1 μm, the proportion of the atoms belonging to the TiAlN crystal grain boundary in the atoms exposed on the TiAlN layer surface is relatively large. Further, the reactivity with the work material increases, and as a result, the wear resistance cannot be sufficiently exhibited, and when the average particle width W exceeds 2 μm, atoms belonging to the TiAlN crystal grain boundary in the entire TiAlN layer Since the ratio of the occupancy is relatively small, the toughness is lowered and the chipping resistance cannot be sufficiently exhibited. Therefore, the average particle width W is preferably 0.1 to 2 μm.
In addition, when the average aspect ratio A (= L / W) is less than 2, since the columnar structure is not sufficient, the equiaxed crystal having a small aspect ratio is dropped, and as a result, sufficient wear resistance is exhibited. Can not do it. On the other hand, if the average aspect ratio A (= L / W) exceeds 20, the strength of the crystal grains themselves cannot be maintained, and the chipping resistance is lowered.
Therefore, the average aspect ratio A (= L / W) of the crystal grains of the TiAlN layer of the present invention having a columnar structure is preferably 2-20.
In the present invention, the average aspect ratio A (= L / W) means that a longitudinal cross-sectional observation of the TiAlN layer is performed using a scanning electron microscope in a range where the width is 100 μm and the height includes the entire TiAlN layer. Observed from the side of the vertical cross section perpendicular to the surface, the particle width w of each crystal grain in the direction parallel to the substrate surface is measured, and averaged to calculate the average particle width W, and also perpendicular to the substrate surface. The individual particle lengths l in the direction are measured and averaged to calculate the average particle length L. From the average particle width W and the average particle length L, the average aspect ratio A (= L / W) was calculated.

Composition of TiAlN layer:
The TiAlN layer of the present invention is controlled so that the average content ratio X _avg (where X _avg is an atomic ratio) of the total amount of Ti and Al in Al satisfies 0.70 ≦ X _avg ≦ 0.90. .
The reason is that if the average Al content X _avg is less than 0.70, the TiAlN layer is inferior in oxidation resistance, so that it has sufficient wear resistance when subjected to wet high speed cutting such as steel and cast iron. Not. On the other hand, when the average content ratio X _{avg of} Al exceeds 0.90, the precipitation amount of hexagonal crystals inferior in hardness increases and the hardness decreases, so the wear resistance decreases.
Therefore, the average content ratio X _avg of Al was determined as 0.70 ≦ X _avg ≦ 0.90.
In the present invention, the average content ratio X _avg of Al is 0.70 ≦ X _avg ≦ 0.90, and since the Al content in the TiAlN layer is high, the surface of the TiAlN layer is generated by heat generation during cutting. In this case, an Al-rich oxide layer is formed, which acts as a protective layer and is expected to have an effect of suppressing the generation and progress of cracks in the TiAlN layer.

Pore present in the TiAlN layer:
In FIG. 1, the partial expanded schematic diagram of the TiAlN layer of this invention is shown.
As shown in FIG. 1, in the inner layer portion of the TiAlN layer of the present invention, pores having a predetermined average pore diameter are formed along the grain boundaries. Even when a crack due to a general load occurs in the layer, the presence of such a pore causes the thermal crack or the crack (collectively referred to as “crack”) to propagate along the grain boundary. It is suppressed.
As a result, excellent chipping resistance is exhibited even under wet high-speed cutting conditions such as steel and cast iron in which a high thermal and mechanical load acts on the cutting edge.
If the average pore diameter of the pore is less than 2 nm, the effect of suppressing crack growth is not sufficient. On the other hand, if the average pore diameter is larger than 50 nm, the hardness of the inner layer portion of the TiAlN layer is lowered, and it tends to be a starting point of cracks. Chipping and chipping resistance are reduced.
Therefore, the average pore diameter of pores formed along the grain boundaries in the inner layer portion of the TiAlN layer is set to 2 nm or more and 50 nm or less.
Further, when the longitudinal section of the TiAlN layer is observed, if the area ratio of the pores in the inner layer portion is less than 5%, the effect of suppressing the progress of cracks cannot be sufficiently brought out, and if it exceeds 20%, the TiAlN layer Excessive pores in the whole cause a decrease in hardness, leading to an increase in crack starting point and a decrease in chipping resistance and fracture resistance due to a decrease in wear resistance. %.
On the other hand, in the surface layer portion of the TiAlN layer of the present invention, when the average pore diameter of the pore is 50 nm or more in the Al oxide layer serving as a protective film, or when the pore area ratio is 0.5% or more, the coating film Therefore, the pore area ratio was less than 0.5%, and the pore average pore diameter was less than 50 nm.

Here, the area ratio of pores and the average pore diameter can be calculated by the following method.
FIG. 2 is a schematic explanatory diagram for measuring the area ratio of pores. Here, the inner layer portion of the TiAlN layer will be described as an example, but the same applies to the surface layer portion of the TiAlN layer.
As shown in FIG. 2, an arbitrary 1 μm × 1 μm region in the longitudinal section of the inner layer portion of the polished TiAlN layer is used as an observation region and observed with a scanning electron microscope with a magnification of 50000 times. For example, by using Adobe (registered trademark) Photoshop (registered trademark) or other well-known ones, the pores and non-pore regions are specified and colored.
Then, by measuring the total area colored, the ratio of the total area colored to the observation area becomes the pore area ratio. Further, the number of circles or ellipses identified as pores was counted, and the total area of the pores was divided by the total number to calculate the average area per pore, and the average pore diameter obtained from the area was calculated. Then, the pore area ratio and the average pore diameter measured in 10 observation regions were calculated as the pore area ratio and the pore average pore diameter, respectively, so that the effect of uneven pore distribution did not occur. The same method was used for the longitudinal section of the surface layer portion of the TiAlN layer, and the pore area ratio and the average pore diameter measured in 10 observation regions were calculated as the pore area ratio and the pore average pore diameter, respectively. .

In the TiAlN layer of the present invention, the proportion of straight lines where pores exist on the created straight line is 50% or more, and three or more straight lines where pores do not exist on the line do not exist continuously. Since there are pores that suppress crack growth in the inside, pores do not segregate and exist, and the effect of crack growth suppression is greater, so the proportion of straight lines where pores exist on the created straight line It is desirable that there are no three or more straight lines that are 50% or more of the straight line and the pores do not exist on the line.

A method for confirming the presence or absence of pore segregation will be described with reference to FIG.
As shown in FIG. 2, first, an arbitrary 1 μm × 1 μm region in the longitudinal section of the polished TiAlN layer is used as an observation region and observed with a scanning electron microscope at a magnification of 50000 times. The schematic diagram shown in FIG. 2 is an example of an observation region of 1 μm × 1 μm.
In the observation area, a plurality of pores are observed as shown as bold circles and thin circles in FIG.
Next, with respect to the observation region, straight lines parallel to the tool base surface and parallel to the layer thickness direction at intervals of 50 nm are drawn, and 21 straight lines are created together with the straight lines at both ends.
In FIG. 2, the pores existing on the straight line are shown as thick circles, while the pores located off the straight line are shown as thin circles, and the thick circle represents the straight line existing on the line. Count.
If the percentage of straight lines where pores exist on the created straight line is 50% or more and there are no three or more straight lines where pores do not exist on the line, pores that suppress crack growth It can be judged that it exists without uneven distribution in the layer.

Method for forming a TiAlN layer of the present invention:
A TiAlN layer having a columnar structure, crystal structure, component composition, pore area ratio / average pore size and orientation defined in the present invention is formed by chemical vapor deposition under the following film formation conditions for the inner layer portion and the outer layer portion. Can be obtained.
The pores present in the inner layer portion and the surface layer portion of the TiAlN layer of the present invention vary in pore formation depending on the supply amount and supply speed of the raw material gas, and the pore area ratio and average pore diameter are the ratio of the metal raw material gas and It can be controlled by changing the supply cycle.
[Film formation conditions]
Surface layer deposition conditions Reaction gas composition (volume%):
Gas Group _{A: NH 3 0.8~1.6%, H} 2 45~55%,
Gas group B: AlCl ₃ 0.5 to 0.7%, TiCl ₄ 0.1 to 0.3%, N ₂ : 0.5 to 1.0%, H ₂ : remaining,
Reaction atmosphere pressure: 4.0 to 5.0 kPa,
Reaction atmosphere temperature: 700 to 900 ° C.
Supply cycle: 1-5 seconds
Gas supply time per cycle: 0.15 to 0.25 seconds,
Phase difference between supply of gas group A and supply of gas group B: 0.10 to 0.20 seconds,

Film formation conditions for inner layer Reaction gas composition (volume%):
Gas Group _{A: NH 3 0.8~1.6%, H} 2 45~55%,
Gas group B: AlCl ₃ 0.5 to 0.7%, TiCl ₄ 0.1 to 0.3%,
_{N 2 1.0~10%, Ar: 15~25} %, H 2: remainder,
Reaction atmosphere pressure: 4.0 to 5.0 kPa,
Reaction atmosphere temperature: 700 to 900 ° C.
Supply cycle: 10 to 30 seconds,
Gas supply time per cycle: 0.5 to 2.0 seconds,
Phase difference between supply of gas group A and supply of gas group B: 0.5 to 1.0 second,

Lower layer:
The hard coating layer of the present invention has a sufficient effect only with the TiAlN layer, but one or two of the Ti carbide layer, nitride layer, carbonitride layer, carbonate layer and carbonitride oxide layer. When a lower layer composed of a Ti compound layer equal to or more than one layer is provided, the adhesion between the tool base and the TiAlN layer can be improved, and therefore, the occurrence of abnormal damage such as defects and peeling can be suppressed.
However, if the total average layer thickness of the lower layer composed of the Ti compound layer is less than 0.1 μm, the effect of the lower layer is not sufficiently achieved. On the other hand, if it exceeds 20 μm, the crystal grains tend to become coarse and chipping occurs. Therefore, the total average layer thickness of the lower layer is preferably 0.1 to 20 μm.

  The present invention provides a surface-coated cutting tool in which a hard coating layer is provided on the surface of a tool base, the hard coating layer includes at least a TiAlN layer, the TiAlN layer has a columnar structure, and crystal grains having a cubic structure And further comprising an inner layer portion in contact with the base material or the underlayer and a surface layer portion located on the outer surface, and in the inner layer portion, there are pores having a predetermined area ratio and average pore diameter, Accumulation of strain due to thermal expansion can be reduced, thermal cracking and chipping can be suppressed, and generation and propagation of cracks in the TiAlN layer can be suppressed by the aluminum oxide layer in the surface layer portion. Between the X-ray diffraction peak intensity Ifcc (111) and Ifcc (200) of the crystal grain of the crystal structure, Ifcc (111) / (Ifcc (111) + Ifcc (200)) ≧ 0 Since the wear resistance can be drastically improved by establishing the relationship of 5, the chipping resistance is excellent in wet high-speed cutting processing in which a high thermal and mechanical load acts on the cutting edge. Abrasion resistance is demonstrated.

It is a whole schematic diagram of the TiAlN layer of this invention, Comprising: The state in which the pore is formed on the crystal grain boundary in the inner layer part is shown. In the partial expansion schematic diagram of the TiAlN layer shown by FIG. 1, it is a schematic explanatory drawing for confirming the presence or absence of the segregation of a pore.

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

As raw material powders, WC powder, TiC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder and Co powder all having an average particle diameter of 1 to 3 μm are prepared, and these raw material powders are blended as shown in Table 1. Blended into the composition, added with wax, mixed in a ball mill in acetone for 24 hours, dried under reduced pressure, pressed into a compact of a predetermined shape at a pressure of 98 MPa, and the compact was 1370 in a vacuum of 5 Pa. WC-based cemented carbide tool bases A and B with ISO / SEEN1203AFSN insert shape are manufactured after vacuum sintering under the condition of holding for 1 hour at a predetermined temperature in the range of ~ 1470 ° C. did.

  Moreover, as the raw material powder, TiCN (mass ratio TiC / TiN = 50/50) powder, NbC powder, WC powder, Co powder and Ni powder, all having an average particle diameter of 0.5 to 2 μm, are prepared. The raw material powder is blended in the blending composition shown in Table 2, wet mixed with a ball mill for 24 hours, dried, and then press-molded into a green compact at a pressure of 98 MPa. The temperature was sintered at 1500 ° C. for 1 hour, and after sintering, a tool base C made of TiCN-based cermet having an ISO · SEEN1203AFSN insert shape was produced.

Next, a chemical vapor deposition apparatus is used on the surfaces of these tool bases A to C,
Formation conditions A to H shown in Table 4, that is, a gas group A composed of NH ₃ and H ₂ , a gas group B composed of AlCl ₃ , TiCl ₄ , N ₂ , Ar and H ₂ , and supply of each gas As a method, the reaction gas composition (capacity% with respect to the total of the gas group A and the gas group B) is set as the gas group A, NH ₃ : 0.8 to 1.6%, H ₂ : 45 to 55%, the gas group. As B, AlCl ₃ : 0.5 to 0.7%, TiCl ₄ : 0.1 to 0.3%, N ₂ : 1.0 to 10%, Ar: 15 to 25%, H ₂ : remaining, reaction atmosphere Pressure: 4 to 5 kPa, reaction atmosphere temperature: 700 to 900 ° C., supply cycle 10 to 30 seconds, gas supply time 0.5 to 2.0 seconds per cycle, supply of gas group A and supply of gas group B A thermal CVD method is performed for a predetermined time with a phase difference of 0.5 to 1.0 second, and Ti forming a inner portion of lN layer, then forming conditions shown in Table 5 A to H, i.e., a gas group A consisting of NH ₃ and _{H 2,} consisting of AlCl 3, TiCl _{4, N 2} and _{H 2} As a gas group B and a gas supply method, the reaction gas composition (capacity% with respect to the total of the gas group A and the gas group B) is set as NH ₃ : 0.8 to 1.6% as the gas group A, H _2: 45~55%, AlCl ₃ as gas group _{B: 0.5~0.7%, TiCl 4:} 0.1~0.3%, N 2: 0.5~1.0%, H 2 : Remaining, reaction atmosphere pressure: 4 to 5 kPa, reaction atmosphere temperature: 700 to 900 ° C., supply cycle 1 to 5 seconds, gas supply time per cycle 0.15 to 0.25 seconds, supply of gas group A and gas Group B supply phase difference of 0.10 to 0.20 seconds, predetermined time, thermal CVD method The present coated tools 1 to 12 having the TiAlN layer shown in Table 7 were manufactured by forming a surface layer portion of the TiAlN layer.
In addition, about this invention coated tools 9-12, the lower layer shown in Table 6 was formed on the formation conditions shown in Table 3.

Further, for the purpose of comparison, the coated tool 1 of the present invention is applied to the surface of the tool bases A to C with the target layer thickness (μm) shown in Table 8 under the conditions of the comparative film forming process shown in Tables 4 and 5. In the same manner as in -12, a hard coating layer containing at least a TiAlN layer was formed by vapor deposition to produce comparative coating tools 1-12. At this time, comparative coating tools 1 to 12 were manufactured by forming a hard coating layer so that the reaction gas composition on the surface of the tool base did not change with time during the TiAlN layer forming step.
In addition, similarly to this invention coated tools 9-12, about the comparative coated tools 9-12, the lower layer shown in Table 6 was formed on the formation conditions shown in Table 3.

Next, the cross section in the direction perpendicular to the tool base of each component layer of the coated tools 1 to 12 and comparative coated tools 1 to 12 of the present invention is measured using a scanning electron microscope (magnification 5000 times), and within the observation field of view. When the five layer thicknesses were measured and averaged to determine the average layer thickness, all showed the same average layer thickness as the target average layer thicknesses shown in Tables 7 and 8.
In addition, the average Al content ratio X _avg of the TiAlN layer was obtained by irradiating an electron beam from the sample surface side in a sample whose surface was polished using an electron beam microanalyzer (EPMA, Electron-Probe-Micro-Analyzer). The average Al content ratio X _avg of Al was determined from the 10-point average of the obtained characteristic X-ray analysis results.
Tables 7 and 8 show X _avg values.

Moreover, about the TiAlN layer of this invention coating tool 1-12 and comparative coating tool 1-12, using a scanning electron microscope (5000 times magnification), the longitudinal cross section of a TiAlN layer in the range which includes the whole TiAlN layer with a width of 100 μm Observe the surface, observe from the longitudinal section side perpendicular to the tool substrate surface, measure the particle width w of the individual crystal grains in the direction parallel to the substrate surface, and average this to calculate the average particle width W, Further, the individual particle lengths l in the direction perpendicular to the substrate surface are measured, and averaged to calculate the average particle length L. From the average particle width W and the average particle length L, the average particle length L is calculated. The aspect ratio A (= L / W) was calculated.
Tables 7 and 8 show the average aspect ratio A (= L / W).

Moreover, about this invention coated tool 1-12 and comparative coated tool 1-12, the longitudinal cross-section of the inner layer part of a TiAlN layer and a surface layer part is observed with a scanning electron microscope of 50000 times, respectively, and the area | region of 1 micrometer x 1 micrometer is obtained. As the observation region, a straight line parallel to the surface of the tool base and parallel to the layer thickness direction at 50 nm intervals was drawn as the observation region, and the pore area ratio and the average pore diameter were determined for each of the inner layer portion and the surface layer portion. .
That is, as shown in FIG. 2, for each of the inner layer portion and the surface layer portion, color the portion identified as a pore using image processing software for the obtained image, and measure the total area colored, The ratio of the pore area to the observation area was calculated. Also, by counting the circles or ellipses identified as pores, dividing the total area of the pores by the total number, the average area per pore is calculated, and the pores obtained from the diameter of the circle having that area The average pore diameter was calculated. Then, the pore area ratio and average pore diameter measured in 10 observation regions were calculated as the pore area ratio and pore average pore diameter for each of the inner layer portion and the surface layer portion.
Tables 7 and 8 show the results.
In order to check whether pores are unevenly distributed, the number of straight lines having pores on the created straight line is counted, and the ratio of the number of straight lines having pores measured in 10 observation regions is calculated. In addition, it was examined whether or not three or more straight lines without pores exist in each observation region.
About the TiAlN layer of this invention coated tool 1-12, the ratio of the straight line in which a pore exists on the created straight line was 50% or more. In addition, three or more straight lines having no pores on the line did not continue.
From this, the TiAlN layers of the coated tools 1 to 12 of the present invention exist because the pores exist without being unevenly distributed in the layer, and this is caused by the growth and progress of excessive cracks that are likely to occur due to the localized unevenness of the pores. It was found that no chipping or defects occurred.

Further, with respect to the TiAlCN layer, the diffraction peak intensity Ifcc (111) of the (111) plane and the diffraction peak intensity Ifcc (200) of the (111) plane of the cubic TiAlN crystal grains by X-ray diffraction using a Cr tube. And the diffraction peak intensity Ihcp (100) of the (100) plane of TiAlN crystal grains having a hexagonal structure, and the value of Ifcc (111) / {Ifcc (111) + Ifcc (200)} and Ifcc (111) / { The value of Ifcc (111) + Ihcp (100)} was calculated.
Tables 7 and 8 show these values.

Next, the wet coated high-speed cutting tests A and B shown below were performed on the inventive coated tools 1 to 12 and the comparative coated tools 1 to 12, and the flank wear width of the cutting blade was measured.
The results are shown in Table 9.
For the comparative coated tools 1 to 12, the cutting time (minutes) until the end of the tool life is described for those that have reached the tool life due to the occurrence of chipping due to the propagation and progress of thermal cracks.

≪Cutting condition A≫
Cutting test: wet high speed face milling, center cut cutting,
Work material: JIS / SCM440 block material with a width of 100 mm and a length of 400 mm,
Rotational speed: 1019 min ⁻¹
Cutting speed: 400 m / min,
Incision: 1.5mm,
Single-blade feed rate: 0.2 mm / tooth,
Cutting time: 5 minutes
≪Cutting condition B≫
Cutting test: wet high speed face milling, center cut cutting,
Work material: JIS / FCD700 width 100mm, block length 400mm,
Rotational speed: 1019 min ⁻¹
Cutting speed: 400 m / min,
Incision: 1.5mm,
Single blade feed amount: 0.15 mm / tooth,
Cutting time: 5 minutes

  As shown in Table 9, according to the coated tool of the present invention, the TiAlN crystal grains constituting the TiAlN layer exhibit a predetermined orientation, and there are pores having a predetermined area ratio and an average pore diameter in the layer. In the wet high-speed cutting process such as steel and cast iron where high thermal and mechanical loads are applied to the cutting edge, the propagation and progress of cracks due to the occurrence of thermal cracks is suppressed, so that it can be used for a long time. Excellent chipping resistance and wear resistance.

  In contrast, the TiAlCN layer does not have the orientation defined in the present invention, and the comparative coated tool in which the pores of the area ratio and the average pore diameter defined in the present invention are inferior in wear resistance, It is clear that chipping, chipping, etc. occur due to the occurrence of thermal cracks during cutting, and the service life is shortened in a short time.

As described above, the coated tool of the present invention exhibits extremely excellent cutting performance in wet high-speed cutting of steel or cast iron, but can be applied as a coated tool for various work materials or cutting conditions, In addition, it has excellent thermal crack resistance, abnormal damage resistance, and wear resistance over a long period of use, so it is possible to improve the performance of cutting equipment, labor and energy saving of cutting, and cost reduction. It can respond satisfactorily.

Claims (3)

In a surface-coated cutting tool in which a hard coating layer is provided on the surface of a tool base composed of a tungsten carbide-based cemented carbide or a titanium carbonitride-based cermet,
(A) The hard coating layer includes at least a composite nitride layer of Ti and Al having an average layer thickness of 1.5 μm or more and 15 μm or less,
(B) The Ti and Al composite nitride layer is composed of crystal grains having a columnar structure and includes at least crystal grains having a NaCl-type face-centered cubic structure;
(C) The composite nitride layer of Ti and Al has the composition
Composition formula: (Ti _1-x Al _x ) N
The average content ratio X _avg (where X _avg is the atomic ratio) of the total amount of Ti and Al in Al satisfies 0.7 ≦ X _avg ≦ 0.9,
(D) The Ti and Al composite nitride layer is composed of an inner layer portion in contact with the base material or the underlayer and a surface layer portion located on the outer surface,
(E) The film thickness of the inner layer portion is 0.5 μm or more, and pores exist at the grain boundaries of the crystal grains of the inner layer portion, and the area ratio and average occupied by the pores in the longitudinal section of the inner layer portion When the pore diameter is calculated, the area ratio of the pore to the observation area is 5% or more and less than 20%, and the average pore diameter of the pore is 2 nm or more and 50 nm or less,
(F) The film thickness of the surface layer portion is 1.0 μm or more, and when calculating the area ratio and the average pore diameter occupied by the pores in the longitudinal section of the surface layer section, the area ratio occupied by the pores with respect to the observation area area is Less than 0.5% and the average pore diameter of the pores is 50 nm or less,
(G) X-ray diffraction is performed on the crystal grains having the NaCl-type face-centered cubic structure constituting the composite nitride layer of Ti and Al, and the diffraction peak intensity Ifcc (111) on the (111) plane is expressed by (200) A surface-coated cutting tool characterized by satisfying a relationship of Ifcc (111) / (Ifcc (111) + Ifcc (200)) ≧ 0.5 when the diffraction peak intensity Ifcc (200) of the surface is obtained.   The composite nitride layer of Ti and Al is subjected to X-ray diffraction, and the diffraction peak intensity Ifcc (111) of the (111) plane of the crystal grain having the NaCl type face-centered cubic structure and the crystal grain having the hexagonal crystal structure The diffraction peak intensity Ihcp (100) of the (100) plane satisfies the relationship Ifcc (111) / (Ifcc (111) + Ihcp (100)) ≧ 0.9. The surface-coated cutting tool described. Between the tool base and the composite nitride layer of Ti and Al, one or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer and carbonitride oxide layer The surface-coated cutting tool according to claim 1, wherein the lower layer made of the Ti compound layer is provided with a total average layer thickness of 0.1 to 20 μm.