JP5907406B2 - Surface coated cutting tool whose hard coating layer exhibits excellent chipping resistance in high-speed intermittent cutting - Google Patents

Description

  The present invention shows that the hard coating layer exhibits excellent adhesion strength even when various types of cutting work such as steel and cast iron are performed at high speed and under intermittent cutting conditions in which intermittent and impact loads are applied to the cutting edge. The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits excellent chipping resistance and exhibits excellent cutting performance over a long period of time.

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) The lower layer is a Ti carbide (hereinafter referred to as TiC) layer, a nitride (hereinafter also referred to as TiN) layer, a carbonitride (hereinafter referred to as TiCN) layer, a carbon oxide (hereinafter referred to as TiCO). And a Ti compound layer composed of one or more of a carbonitride oxide (hereinafter referred to as TiCNO) layer,
(B) The upper layer has an α-type crystal structure in the state of chemical vapor deposition (hereinafter referred to as an Al ₂ O ₃ layer) or an α-type crystal structure and contains a trace amount of Zr. A Zr-containing aluminum oxide layer (hereinafter referred to as a Zr-containing Al ₂ O ₃ layer),
A coated tool formed by vapor-depositing the hard coating layer constituted by (a) and (b) is known.

However, the above conventional coated tools exhibit excellent wear resistance in continuous cutting and intermittent cutting of various steels and cast irons, for example, but when this is used for high-speed intermittent cutting, chipping of the coating layer is performed. There is a problem that tool life is likely to occur and the tool life is shortened.
Therefore, in order to improve the chipping resistance, peel resistance, wear resistance, and the like of the coating layer, coating tools obtained by adding various improvements to the hard coating layer have been proposed.
For example, as shown in Patent Document 1, a coated tool with improved peeling resistance and wear resistance by adjusting the crystal grain size in the layer thickness direction of the upper layer composed of an Al ₂ O ₃ layer is proposed. However, this coated tool is disadvantageous in that the productivity of the coated tool is inferior because it is necessary to reduce the deposition rate in adjusting the size of the Al ₂ O ₃ crystal grains constituting the upper layer. was there.
As for the chipping resistance improvement of the upper layer composed of the Zr-containing Al ₂ O ₃ layer, for example, as shown in Patent Document 2, in the constituent atom shared lattice point distribution graph, the highest peak exists in Σ3, In addition, a coated tool in which an upper layer is composed of a Zr-containing Al ₂ O ₃ layer showing a constituent atomic shared lattice point distribution graph in which the distribution ratio of Σ3 is 60 to 80% has been proposed. Although it is excellent in the properties, there is a problem that the interlayer adhesion between the upper layer and the lower layer is not sufficient, and peeling is likely to occur depending on cutting conditions.

JP-A-57-137460 JP 2006-289557 A

In recent years, the performance of cutting machines has been remarkable. On the other hand, there is a strong demand for labor saving and energy saving and further cost reduction for cutting work. As a result, cutting speed has been further increased and the load on the cutting blade has been increased. Although there is no problem with the above-mentioned conventional coated tools when used for continuous cutting or intermittent cutting under normal conditions such as steel or cast iron, this is particularly accompanied by high heat generation. When used under high-speed intermittent cutting conditions in which an intermittent / impact load is applied to the cutting edge, the lower layer composed of the Ti compound layer and the upper layer composed of the Zr-containing Al ₂ O ₃ layer constituting the hard coating layer The present situation is that the adhesive strength becomes insufficient and the service life is reached in a relatively short time due to occurrence of abnormal damage such as peeling and chipping between the upper layer and the lower layer.

Therefore, the present inventors have improved the adhesion between the lower layer made of the Ti compound layer and the upper layer made of the Zr-containing Al ₂ O ₃ layer from the above-mentioned viewpoints, thereby causing abnormal damage such as peeling and chipping. As a result of diligent research to prevent tooling and to increase tool life,
In a coated tool in which a lower layer made of a Ti compound layer and an upper layer made of a Zr-containing Al ₂ O ₃ layer are coated, the grain size in the layer thickness direction of the Zr-containing Al ₂ O ₃ layer is controlled, and the Zr-containing Al By controlling the orientation of ₂ O ₃ crystal grains, the adhesion between the upper layer and the lower layer can be improved, and the high temperature hardness and high temperature strength of the entire upper layer can be maintained. -Even when used for high-speed intermittent cutting where impact load is applied, it is possible to suppress the occurrence of abnormal damage such as peeling and chipping between the upper layer and the lower layer and to provide excellent cutting performance over a long period of use They found that they could get a tool.

This invention has been made based on the above findings,
"On the surface of the tool base made of tungsten carbide base cemented carbide or titanium carbonitride base cermet,
(A) The lower layer is composed of one or more of a Ti carbide layer, a nitride layer, a carbonitride layer, a carbonate layer, and a carbonitride layer, and a total of 3 to 20 μm A Ti compound layer having an average layer thickness;
(B) an upper layer, Zr-containing α-type _{the Al} 2 _{O 3} layer having an average layer thickness and α-type crystal structure of 2 to 15 [mu] m (where, in terms of atomic ratio, the value of the ratio of Zr / (Al + Zr + O ) is 0.0001 to 0.003),
A surface-coated cutting tool provided with a hard coating layer comprising the above (a) and (b),
(C) The outermost surface layer of the lower layer is made of a Ti carbonitride layer having a layer thickness of at least 500 nm, and the Ti carbonitride layer is formed from the interface between the Ti carbonitride layer and the upper layer. Oxygen is contained only in the depth region up to 500 nm in the thickness direction, and the average oxygen content contained in the depth region is that of Ti, C, N, O contained in the depth region. 0.5-3 atomic% of the total content,
(D) The Zr-containing α-type Al ₂ O ₃ of the upper layer immediately above the interface between the lower layer and the upper layer is within the measurement range of the cross-section polished surface using an electron beam backscattering diffractometer. When the grain size of the Zr-containing α-type Al ₂ O ₃ crystal grain is measured by irradiating each crystal grain having a hexagonal crystal lattice with an electron beam, in a region less than 1 μm in the thickness direction of the upper layer from the interface The average transverse grain size of the Zr-containing α-type Al ₂ O ₃ crystal grains is 0.1 to 0.3 μm, while the Zr-containing α-type Al ₂ O ₃ in the region of 1 μm or more in the film thickness direction of the upper layer from the interface. The average grain size in the transverse direction of the crystal grains is 0.5 to 1.0 μm, and has a columnar crystal structure grown in the film thickness direction,
(E) With respect to the Zr-containing α-type Al ₂ O ₃ crystal grains of the entire upper layer, each crystal grain having a hexagonal crystal lattice existing within the measurement range of the cross-sectional polished surface using an electron beam backscattering diffractometer When the inclination angle formed by the normal of the (0001) plane, which is the crystal plane of the crystal grain, is measured with respect to the normal of the surface of the tool base, the inclination angle is 0 to In the region where the area ratio of the crystal grains within the range of 10 degrees is 45 area% or more as a whole and the film thickness of the upper layer from the interface is less than 1 μm, the (0001) orientation is less than 10% and the (02-21) orientation is 30. A surface-coated cutting tool characterized by being at least%. "
It has the characteristics.

Hereinafter, the constituent layers of the hard coating layer of the coated tool of the present invention will be described in detail.
(A) Ti compound layer (lower layer):
The Ti compound layer (for example, TiC layer, TiN layer, TiCN layer, TiCO layer and TiCNO layer) is basically a lower layer of a Zr-containing α-type Al ₂ O ₃ (hereinafter referred to as Zr-containing Al ₂ O ₃ ) layer. The hard coating layer has high temperature strength due to its excellent high temperature strength, and the tool substrate of the hard coating layer is in close contact with both the tool substrate and the Zr-containing Al ₂ O ₃ layer. However, if the total average layer thickness is less than 3 μm, the above-mentioned effect cannot be sufficiently exerted. On the other hand, if the total average layer thickness exceeds 20 μm, particularly high heat generation occurs. In high-speed intermittent cutting, it becomes easy to cause thermoplastic deformation, which causes uneven wear. Therefore, the total average layer thickness is set to 3 to 20 μm.

(B) The outermost surface layer of the lower layer:
The outermost surface layer of the lower layer in the present invention is formed as follows, for example.
That is, first, using a normal chemical vapor deposition apparatus, various Ti compound layers consisting of one or more of TiC layer, TiN layer, TiCN layer, TiCO layer and TiCNO layer are formed by vapor deposition (in addition, (It is of course possible to vapor-deposit only the TiCN layer), and then using a normal chemical vapor deposition apparatus,
Reaction gas composition (volume%): TiCl ₄ 2.5 to 10%, CH ₃ CN 0.5 to 1.0%, N ₂ 40 to 60%, balance H ₂ ,
Reaction atmosphere temperature: 800 to 900 ° C.
Reaction atmosphere pressure: 6 to 10 kPa,
For example, a TiCN layer containing oxygen (hereinafter referred to as oxygen-containing TiCN) layer is formed as the outermost surface layer of the lower layer.
At this time, for 5 to 30 minutes before the end of the deposition time required to obtain a predetermined layer thickness, the chemical gas is added by adding CO gas so as to be 1 to 5% by volume with respect to the total reaction gas amount. By performing vapor deposition, an oxygen-containing TiCN layer containing 0.5 to 3 atomic% of oxygen is vapor-deposited only in the depth region up to 500 nm in the layer thickness direction.

The uppermost surface layer of the lower layer composed of the oxygen-containing TiCN layer is, for example, a layer thickness of at least 500 nm or more in order to form preferable Zr-containing Al ₂ O ₃ crystal grains thereon (see (c) below). And 0.5 to 3 atomic% of oxygen only in the depth region from the interface between the oxygen-containing TiCN layer and the upper layer up to 500 nm in the thickness direction of the oxygen-containing TiCN layer. It is desirable that the depth region exceeding 500 nm is composed of an oxygen-containing TiCN layer not containing oxygen.
Here, the average oxygen content in the depth region up to 500 nm of the oxygen-containing TiCN layer is limited as described above because when oxygen is contained in a region deeper than 500 nm in the depth direction of the film, As the surface texture changes from a columnar structure to a granular structure, the orientation of the Zr-containing Al ₂ O ₃ crystal grains immediately above the outermost surface layer of the lower layer cannot be made desired, and the upper layer and the lower layer In a region of the upper layer from the interface in the film thickness direction of less than 1 μm (hereinafter also referred to as just above the lower layer), the grain size of the Zr-containing Al ₂ O ₃ crystal grains measured along the plane parallel to the tool base surface (hereinafter referred to as horizontal) This is because the directional particle size cannot be as fine as 0.1 to 0.3 μm.
Further, if the average oxygen content up to a depth region of 500 nm is less than 0.5 atomic%, it is not possible to improve the adhesion strength between the upper layer and the lower layer TiCN, while the average oxygen content in the depth region Exceeds 3 atomic%, in the upper layer Zr-containing Al ₂ O ₃ immediately above the interface, (0001) -oriented Zr-containing Al ₂ O ₃ crystal grains (in addition, (0001) -oriented Zr-containing Al ₂ O ₃ crystal grains This is because the area ratio occupied by the upper layer is less than 45 area% with respect to the total area of Al ₂ O ₃ of the entire upper layer, and the high-temperature strength of the upper layer is reduced.
Here, the average oxygen content is determined from titanium (Ti) and carbon in a depth region up to 500 nm in the layer thickness direction of the TiCN layer from the interface between the TiCN layer and the upper layer constituting the outermost surface layer of the lower layer. The oxygen (O) content in the total content of (C), nitrogen (N) and oxygen (O) is expressed in atomic% (= O / (Ti + C + N + O) × 100).

(C) Zr-containing Al ₂ O ₃ crystal grains in the upper layer:
On the surface of the oxygen-containing TiCN layer containing 0.5 to 3 atomic% of oxygen formed in the above (b), for example,
Reaction gas composition (volume%): CO 5-10%, CO ₂ 5-10%, balance H ₂ ,
Atmospheric temperature: 900-980 ° C.
Atmospheric pressure: 5-15 kPa,
With the proviso that, by performing oxidation treatment with CO and CO ₂ mixed gas, _alpha-Al 2 _{O 3} nuclei nuclear Al compound required to generate it to uniformly disperse the Ti compound layer outermost surface, _Al 2 _{O 3} In the step before nucleation, α-Al ₂ O ₃ nuclei can be uniformly dispersed on the outermost surface of the Ti compound layer.
Next,
Reaction gas composition (volume%): AlCl ₃ 1-3%, CO ₂ 1-5%, ZrCl ₄ 0.2-1.0%, balance H ₂ ,
Reaction atmosphere temperature: 900-980 ° C.,
Reaction atmosphere pressure: 5 to 15 kPa,
Time: 5-30 min
Zr-containing Al ₂ O ₃ was vapor-deposited under the following conditions:
Next,
Reaction gas composition (volume%): AlCl ₃ 1-5%, ZrCl ₄ 0.2-1.0%, CO ₂ 3-10%, HCl 1-5%, H ₂ S 0.1-0.5% , Balance H ₂ ,
Reaction atmosphere temperature: 900-980 ° C.,
Reaction atmosphere pressure: 5 to 15 kPa,
Time: (until the target upper layer thickness is reached)
By evaporating the upper layer under the conditions
Immediately above the interface between the upper layer and the lower layer (a region less than 1 μm in the film thickness direction of the upper layer from the interface between the lower layer and the upper layer), the lateral average grain size of the Zr-containing Al ₂ O ₃ crystal grains (on the surface of the tool substrate) The average particle diameter of Zr-containing Al ₂ O ₃ crystal grains measured along parallel planes) is 0.1 to 0.3 μm, and in the region of 1 μm or more in the film thickness direction of the upper layer from the interface, An upper layer made of Zr-containing Al ₂ O ₃ crystal grains having a directional average grain size of 0.5 to 1.0 μm is formed by vapor deposition.
Moreover, the upper layer has a columnar crystal structure grown in the film thickness direction, and the area ratio of the upper layer to the total Zr-containing α-type Al ₂ O ₃ crystal grains is 45% by area or more in total. To Zr-containing Al ₂ O ₃ layer in which (0001) orientation of the crystal grains in the range of less than 1 μm is less than 10% and (02-21) orientation is 30% or more.

In the Zr-containing Al ₂ O ₃ layer of (c) above, Al, which is a constituent component, improves the high-temperature hardness and heat resistance of the layer, and a small amount (in the total amount of Al and O in the layer). Zr component containing Zr / (Al + Zr + O) in a ratio of 0.0001 to 0.003 (however, atomic ratio) improves the grain boundary strength and high-temperature strength of the Zr-containing Al ₂ O ₃ layer itself. However, when the content ratio of the Zr component is less than 0.0001, the above-described effect cannot be expected. On the other hand, when the content ratio of the Zr component exceeds 0.003, zirconium oxide particles are contained in the layer. Since the grain boundary strength decreases due to precipitation, the content ratio of the Zr component in the total amount of the Al component and the O component (value of the ratio of Zr / (Al + Zr + O)) is 0.0001 to 0.003 (however, Atomic ratio).

The Zr-containing Al ₂ O ₃ crystal grains of (c) above grow as a vertically elongated columnar structure in the layer thickness direction. Depending on the position of the upper layer in the layer thickness direction, the transverse average grains of the Zr-containing Al ₂ O ₃ crystal grains The diameter is different.
The lateral average grain size of the Zr-containing Al ₂ O ₃ crystal grains is mainly influenced by the grain size of the Ti compound surface of the lower layer and the reaction conditions of the Zr-containing Al ₂ O ₃ of the upper layer. When the grain size is fine, the transverse average grain size of the Zr-containing Al ₂ O ₃ crystal grains immediately above the lower layer is small, while when the grain size of the Ti compound surface is coarse, The average lateral grain size of the Zr-containing Al ₂ O ₃ crystal grains immediately above the layer is increased. However, when the average transverse grain size of the Zr-containing Al ₂ O ₃ crystal grains immediately above the interface between the upper layer and the lower layer is less than 0.1 μm, the grain size of the Zr-containing Al ₂ O ₃ crystal grains is relatively too small. For this reason, the bonding strength with the irregularities on the surface of the Ti compound directly above the lower layer is deteriorated, so that the adhesion strength with the upper layer Zr-containing Al ₂ O ₃ crystal grains is weakened. On the contrary, if the average grain size in the transverse direction of the Zr-containing Al ₂ O ₃ crystal grains immediately above the interface exceeds 0.3 μm, the Zr-containing Al ₂ O _{3 in the} upper layer is coarsened and chipping resistance is reduced. From the average lateral grain size of the Zr-containing Al ₂ O ₃ crystal grains immediately above the interface between the upper layer and the lower layer (the average grain diameter of the Zr-containing Al ₂ O ₃ crystal grains measured along a plane parallel to the tool substrate surface) ) Needs to be 0.1 to 0.3 μm by adjusting the particle size of the surface of the Ti compound in the lower layer. To adjust the particle size of the Ti compound surface of the lower layer, the ratio of TiCl ₄ and CH ₃ CN and the amount of CO gas during the growth of the uppermost surface layer of the lower layer (b) can be adjusted. By setting the particle size of the surface layer to about 0.1 to 0.3 μm, it is possible to obtain the desired transverse average particle size of the desired Zr-containing Al ₂ O ₃ crystal grains.
Then, Zr-containing Al ₂ O ₃ crystal grains having a fine lateral average grain size of 0.1 to 0.3 μm are formed immediately above the interface between the upper layer and the lower layer, so that the lower layer and the upper layer are Interlayer adhesion strength is improved, high heat generation is accompanied, and it is possible to improve the peeling resistance and chipping resistance of the coated tool under high-speed intermittent cutting conditions in which intermittent and impact loads are applied to the cutting edge.
Incidentally, in the film thickness direction 1μm or more regions of the upper layer from the interface between the upper layer and the lower layer, the upper layer when the lateral average particle size of the Zr-containing _Al 2 _{O 3} crystal grains is less than 0.5 [mu] m Zr-containing _Al 2 O ₃ adhesion strength between the crystal grains is weakened, conversely, the grain coarsening of the Zr-containing _Al 2 _{O 3} exceeds 1.0 .mu.m, since the chipping resistance is lowered, Zr-containing _Al 2 _{O 3} crystals The average particle size in the transverse direction of the grains needs to be 0.5 to 1.0 μm.

The average grain size in the transverse direction of the Zr-containing Al ₂ O ₃ crystal grains is in a region (immediately above the interface) between the upper layer and the lower layer in the film thickness direction of less than 1 μm, and between the upper layer and the lower layer. Irradiating an electron beam to each crystal grain having a hexagonal crystal lattice existing within the measurement range of the cross-sectional polished surface using an electron beam backscattering diffraction device in a region of 1 μm or more in the film thickness direction of the upper layer from The average value of the Zr-containing Al ₂ O ₃ crystal grains immediately above the lower layer and the film thickness direction of the upper layer from the interface between the upper layer and the lower layer are 1 μm. The average lateral grain size of the Zr-containing Al ₂ O ₃ crystal grains in the above region can be determined.

The Zr-containing _Al 2 _{O 3} crystal grains of (c), the area ratio of the top layer across the Zr-containing _Al 2 _{O 3} grains relative to (0001) orientation Zr-containing _Al 2 _{O 3} crystal grains, 45 as a whole (0001) orientation is less than 10% and (02-21) orientation occupies 30% or more in the area of area% or more and the thickness of the upper layer less than 1 μm from the interface, but (02-21) orientation Zr-containing Al ₂ O The area ratio of the _three crystal grains is affected by the amount of AlCl ₃ gas and CO ₂ gas among the above deposition conditions. When the (02-21) orientation is less than 30%, the (0001) -oriented columnar structure of the Zr-containing Al ₂ O ₃ crystal grains grows in a direction inclined from the layer thickness direction, and the area of the desired (0001) orientation I can't get a percentage.
When the (0001) orientation is less than 10% and the (02-21) orientation is 30% or more in the region where the film thickness of the upper layer is less than 1 μm from the interface, the Zr-containing Al ₂ O ₃ of the upper layer and the lower layer Adhesion strength is improved.
And when the area ratio of (0001) oriented Zr-containing Al ₂ O ₃ crystal grains occupies 45% by area or more as a whole, the high-temperature hardness and high-temperature strength of Zr-containing Al ₂ O ₃ in the upper layer are maintained. Therefore, in the present invention, the area ratio of the (0001) -oriented Zr-containing Al ₂ O ₃ crystal grains in the upper layer is set to 45 area% or more.

The area ratio of the (0001) and (02-21) -oriented Zr-containing Al ₂ O ₃ crystal grains is determined by using an electron beam backscattering diffractometer and hexagonal crystals existing within the measurement range of the cross-section polished surface of the upper layer. Inclination angles formed by the normal lines of the (0001) and (02-21) planes, which are crystal planes of the crystal grains, with respect to the normal lines of the surface of the tool base by irradiating individual crystal grains having a lattice. The Zr-containing Al ₂ O ₃ crystal grains having an inclination angle of 0 to 10 degrees can be obtained as a measurement average value of the area ratio of all the Zr-containing Al ₂ O ₃ crystal grains in the upper layer.
In addition, when the average layer thickness of the entire upper layer composed of the Zr-containing Al ₂ O ₃ crystal grains is less than 2 μm, excellent high-temperature strength and high-temperature hardness cannot be exhibited over a long period of use, while 15 μm If it exceeds the upper limit, chipping is likely to occur. Therefore, the average thickness of the upper layer is set to 2 to 15 μm.

In the coated tool of the present invention, by forming an oxygen-containing TiCN layer on the outermost surface of the lower layer of the hard coating layer, the transverse average particle diameter of the Zr-containing Al ₂ O ₃ crystal grains immediately above the interface between the upper layer and the lower layer Is adjusted to 0.1 to 0.3 μm, and in the region of 1 μm or more in the film thickness direction of the upper layer from the interface between the upper layer and the lower layer, the transverse average particle size of the Zr-containing Al ₂ O ₃ crystal grains is set to Since the area ratio of (0001) orientation of the Zr-containing Al ₂ O ₃ crystal grains of the upper layer is set to 45 area% or more, the upper layer and the lower layer are adjusted to 0.5 to 1.0 μm. Adhesion strength can be increased, and high temperature hardness and high temperature strength of the upper layer can be maintained, so cutting of various steels and cast irons can be performed at high speed and intermittently / impact on the cutting edge. Excellent even under high-speed intermittent cutting conditions where the load acts Shows the high-temperature strength and high-temperature hardness, chipping of the hard coating layer, without the occurrence of delamination, in which exhibit cutting performance with superior long-term use.

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

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

In addition, as raw material powders, TiCN (mass ratio TiC / TiN = 50/50) powder, Mo ₂ C powder, ZrC powder, NbC powder, TaC powder, WC powder, all having an average particle diameter of 0.5 to 2 μm. Co powder and Ni powder are prepared, and these raw material powders are blended in the blending composition shown in Table 2, wet mixed by a ball mill for 24 hours, dried, and pressed into a compact at a pressure of 98 MPa. The green compact was sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour, and after sintering, a chamfer with a width of 0.1 mm and an angle of 20 degrees at the cutting edge portion. By performing honing, tool bases a to e made of TiCN-based cermet having a chip shape of ISO standard / CNMG120408 were formed.

Then, each of these tool bases A to E and tool bases a to e is charged into a normal chemical vapor deposition apparatus,
(A) First, Table 3 (l-TiCN in Table 3 indicates the conditions for forming a TiCN layer having a vertically elongated crystal structure described in JP-A-6-8010, and the other conditions are ordinary granularity. The Ti compound layer having the target layer thickness shown in Table 6 was formed by vapor deposition under the conditions shown in FIG.
(B) Under the conditions shown in Table 4, the oxygen-containing TiCN layer as the outermost surface layer of the lower layer (i.e., 0.5 to 3 atomic% (O 2 only in the depth region from the surface of the layer to 500 nm) / (Ti + C + N + O) × 100) containing oxygen) with the target layer thickness shown in Table 6,
(C) Next, under the conditions shown in Table 5, by forming the Zr-containing Al ₂ O ₃ layer of the upper layer with the target layer thickness shown in Table 6,
The present coated tools 1 to 10 were produced, respectively.

Further, for the purpose of comparison, the above-described step (b) of the present coated tool 1, 2, 6, 7 is not performed, and the others are formed under the same conditions as the present coated tool 1, 2, 6, 7 As a result, comparative coated tools 1, 2, 6, and 7 shown in Table 7 were manufactured.
Further, for comparison, oxygen was contained under the conditions (shown as outside of the present invention in Table 4) outside the above step (b) of the above coated tools 3-5, 8-10 of the present invention. The Zr-containing Al ₂ O ₃ layer is formed under conditions that deviate from the above) (shown as outside the present invention in Table 5), and the others are formed under the same conditions as the coated tools 3-5, 8-10 of the present invention. Thus, comparative coated tools 3-5, 8-10 shown in Table 7 were produced.

Next, for the above-described inventive coated tools 1-10 and comparative coated tools 1-10, the TiCN layer constituting the outermost surface layer of the lower layer is averaged in a depth region up to 500 nm in the layer thickness direction of the TiCN layer. The oxygen content (= O / (Ti + C + N + O) × 100), and the average oxygen content (= O / (Ti + C + N + O) × 100) in a depth region exceeding 500 nm were determined using an Auger electron spectrometer. The cross-sectional polished surface is irradiated with an electron beam having a diameter of 10 nm from the outermost surface of the lower Ti carbonitride layer to a distance corresponding to the thickness of the Ti carbide layer, and the intensity of the Auger peaks of Ti, C, N, and O Was calculated from the ratio of O Auger peaks from the sum of the peak intensities.
Tables 6 and 7 show these values.

Further, the comparison coated tool 10 with the above the present invention coated tools 1 to 10, the Zr-containing Al ₂ O ₃ crystal grains directly above the interface between the lower layer and the upper layer and the lateral particle size, the lower layer and the upper layer The lateral grain size of the Zr-containing Al ₂ O ₃ crystal grains in the region of 1 μm or more in the thickness direction of the upper layer from the interface is measured using an electron beam backscattering diffractometer. The average particle size was determined.
More specifically, it is as follows.
With respect to the Zr-containing Al ₂ O ₃ crystal grains immediately above the interface between the lower layer and the upper layer (the region less than 1 μm in the film thickness direction from the interface), using an electron beam backscattering diffractometer, within the measurement range of the cross-section polished surface Each crystal grain having an existing hexagonal crystal lattice is irradiated with an electron beam and measured at an observation magnification of 10,000 times. From the Kikuchi diffraction pattern, each crystal grain of the Zr-containing α-type Al ₂ O ₃ layer is measured. The average particle size in the horizontal direction was determined from the average of the measured values at the 10 measurement points in the horizontal line segment.
Similarly, for the Zr-containing Al ₂ O ₃ crystal grains in the region of 1 μm or more in the film thickness direction of the upper layer from the interface between the lower layer and the upper layer, the average particle size in the lateral direction is determined from the average of the measured values at 10 measurement points. Asked.
Tables 6 and 7 show these values.

Next, the area ratio of (0001) -oriented Zr-containing Al ₂ O ₃ crystal grains in the entire upper layer of the hard coating layer of the present coated tools 1 to 10 and comparative coated tools 1 to 10 and immediately above the interface between the lower layer and the upper layer Regarding the area ratio of the (0001) or (02-21) orientation in the region from the interface to the upper layer in the film thickness direction of less than 1 μm, the cross-sectional polished surface was measured in the same manner as described above using an electron beam backscatter diffractometer. Each crystal grain having a hexagonal crystal lattice existing in the range is irradiated with an electron beam, and is a crystal plane of the crystal grain with respect to the normal of the surface of the tool base (0001) and (02-21) The inclination angle formed by the normal of the surface is measured, and the area ratio of the crystal grains ((0001) or (02-21) oriented Zr-containing Al ₂ O ₃ crystal grains) whose inclination angle is 0 to 10 degrees is measured. Was determined by
Here, “the entire upper layer” refers to the measurement range of the entire upper layer from the interface between the lower layer and the upper layer to the outermost surface of the upper layer.
Tables 6 and 7 show these values.

In addition, the thickness of each constituent layer of the hard coating layer of the present coated tool 1 to 10 and comparative coated tool 1 to 10 is observed with a scanning electron microscope at an observation magnification of 2,000 times (longitudinal section measurement). In all cases, the average layer thickness (average value of 5-point measurement) substantially the same as the target layer thickness was shown.
Further, regarding the Zr content ratio in the upper layer Zr-containing Al ₂ O ₃ crystal grains, a mirror-polished cross section was measured using a secondary ion mass spectrometer, and a different field of view 5 at an observation magnification of 10,000 times. The average value of the points was taken as the actual measurement value.

Next, for the various coated tools of the present invention coated tools 1 to 10 and comparative coated tools 1 to 10, all of them are screwed with a fixing jig to the tip of the tool steel tool,
Work material: Eight longitudinally spaced grooves in the length direction of JIS / S30C,
Cutting speed: 410 m / min. ,
Cutting depth: 1.8mm,
Feed: 0.4 mm / rev. ,
Cutting time: 5 minutes
Wet high-speed intermittent cutting test of carbon steel under the conditions (cutting condition A) (normal cutting speed is 250 m / min.),
Work material: Eight longitudinally spaced grooves in the length direction of JIS / SCM445,
Cutting speed: 390 m / min. ,
Incision: 2.5mm,
Feed: 0.3 mm / rev. ,
Cutting time: 5 minutes
Dry high speed intermittent cutting test of nickel chrome molybdenum alloy steel under the conditions (cutting condition B) (normal cutting speed is 200 m / min.),
Work material: JIS / FCD450 lengthwise equidistant, 8 vertical grooves,
Cutting speed: 410 m / min. ,
Cutting depth: 2.8 mm,
Feed: 0.4 mm / rev. ,
Cutting time: 5 minutes
Dry high-speed high-cut cutting test of ductile cast iron under the following conditions (referred to as cutting condition C) (normal cutting speed is 180 m / min.),
In each cutting test, the flank wear width of the cutting edge was measured.
Table 8 shows the measurement results.

From the results shown in Tables 6 to 8, all of the inventive coated tools 1 to 10 have oxygen-containing TiCN crystal grains formed on the outermost surface of the lower layer, and Zr-containing Al ₂ immediately above the interface between the lower layer and the upper layer. The average grain size in the transverse direction of the O ₃ crystal grains is as fine as 0.1 to 0.3 μm, and the (0001) -oriented Zr-containing Al ₂ O ₃ occupies the Zr-containing Al ₂ O ₃ crystal grains in the entire upper layer. Since the area ratio of crystal grains is 45% by area or more, it has excellent adhesion strength between the upper layer and lower layer, and the upper layer has excellent high temperature hardness and high temperature strength, so it can cut various steels and cast irons. Even when machining is performed under high-speed intermittent cutting conditions in which intermittent and impact loads are applied to the cutting edge, chipping and peeling do not occur, and excellent cutting performance is demonstrated over a long period of use.
However, it is apparent that the comparative coated tools 1 to 10 reach the service life in a relatively short time due to occurrence of chipping and peeling of the hard coating layer in high-speed intermittent cutting.

  As described above, the coated tool of the present invention has high heat generation as well as continuous cutting and intermittent cutting under normal conditions such as various steels and cast iron, and the cutting blade has intermittent and impact loads. Even under severe cutting conditions such as high-speed intermittent cutting that acts, chipping and peeling of the hard coating layer will not occur, and excellent cutting performance will be demonstrated over a long period of use. In addition, it is possible to sufficiently satisfy the labor-saving and energy-saving of the cutting process and the cost reduction.

Claims (1)

On the surface of the tool base composed of tungsten carbide based cemented carbide or titanium carbonitride based cermet,
(A) The lower layer is composed of one or more of a Ti carbide layer, a nitride layer, a carbonitride layer, a carbonate layer, and a carbonitride layer, and a total of 3 to 20 μm A Ti compound layer having an average layer thickness;
(B) an upper layer, Zr-containing α-type _{the Al} 2 _{O 3} layer having an average layer thickness and α-type crystal structure of 2 to 15 [mu] m (where, in terms of atomic ratio, the value of the ratio of Zr / (Al + Zr + O ) is 0.0001 to 0.003),
A surface-coated cutting tool provided with a hard coating layer comprising the above (a) and (b),
(C) The outermost surface layer of the lower layer is made of a Ti carbonitride layer having a layer thickness of at least 500 nm, and the Ti carbonitride layer is formed from the interface between the Ti carbonitride layer and the upper layer. Oxygen is contained only in the depth region up to 500 nm in the thickness direction, and the average oxygen content contained in the depth region is that of Ti, C, N, O contained in the depth region. 0.5-3 atomic% of the total content,
(D) About the Zr-containing α-type Al ₂ O ₃ of the upper layer at the interface between the lower layer and the upper layer, using the electron beam backscattering diffractometer, the hexagon existing in the measurement range of the cross-section polished surface When the grain size of the Zr-containing α-type Al ₂ O ₃ crystal grains is measured by irradiating each crystal grain having a crystal lattice with an electron beam, the Zr in the region less than 1 μm in the thickness direction of the upper layer from the interface The transverse direction average grain size of the contained α-type Al ₂ O ₃ crystal grains is 0.1 to 0.3 μm, while the Zr-containing α-type Al ₂ O ₃ crystal in the region of 1 μm or more in the film thickness direction of the upper layer from the interface. The lateral average particle size of the grains is 0.5 to 1.0 μm, and has a columnar crystal structure grown in the film thickness direction,
(E) With respect to the Zr-containing α-type Al ₂ O ₃ crystal grains of the entire upper layer, each crystal grain having a hexagonal crystal lattice existing within the measurement range of the cross-sectional polished surface using an electron beam backscattering diffractometer When the inclination angle formed by the normal of the (0001) plane, which is the crystal plane of the crystal grain, is measured with respect to the normal of the surface of the tool base, the inclination angle is 0 to In the region where the area ratio of the crystal grains within the range of 10 degrees is 45 area% or more as a whole and the film thickness of the upper layer from the interface is less than 1 μm, the (0001) orientation is less than 10% and the (02-21) orientation is 30. A surface-coated cutting tool characterized by being at least%.