JP2005246596A - Surface-coated cermet cutting tool having hard coating layer exhibiting excellent chipping resistance - 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. <P>SOLUTION: The surface-coated cermet cutting tool has a tool substrate formed of a WC-based cemented carbide or a TiCN-based cermet, and a hard coating layer consisting of (a) a lower layer and (b) an upper layer, applied to a surface of the tool substrate. (a) The lower layer consists of one or two or more layers selected from a TiC layer, a TiN layer, a TiCN layer, a TiCO layer, and a TiCNO layer which are formed by chemical vapor deposition. (b) The upper layer is formed by chemical-vapor-depositing a Cr<SB>3</SB>O<SB>2</SB>layer on an Al<SB>2</SB>O<SB>3</SB>layer having a κ type or θ type crystal structure in a chemical-vapor-deposited state and having a mean layer thickness in the range of 1 to 15 μm, so as to have a mean layer thickness in the range of 1.5 to 5 μm, and then heating the resultant layers so as to transform the Al<SB>2</SB>O<SB>3</SB>layer having the κ type or θ type crystal structure into an α type crystal structure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  This invention is made of a surface-coated cermet that exhibits excellent chipping resistance with a hard coating layer against mechanical thermal shock that is repeatedly applied to the cutting edge portion at a very short pitch, especially during high-speed intermittent cutting of steel and cast iron. The present invention relates to a cutting tool (hereinafter referred to as a coated cermet tool).

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) As a lower layer, 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, Ti compound layer comprising one 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) a vapor-deposited α-type aluminum oxide (hereinafter referred to as Al ₂ O ₃ ) layer having an α-type crystal structure in the state of chemical vapor deposition and having an average layer thickness of 1 to 15 μm as an upper layer;
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

In general, the Ti compound layer or the Al ₂ O ₃ layer constituting the hard coating layer of the above-mentioned coated cermet tool has a granular crystal structure, and the TiCN layer constituting the Ti compound layer is further improved in the strength of the layer itself. For the purpose of improvement, it is formed by chemical vapor deposition in a medium temperature range of 700 to 950 ° C. using a mixed gas containing an organic carbonitride such as CH ₃ CN as a reaction gas in a normal chemical vapor deposition apparatus. It is also known to have a vertically elongated crystal structure.
Japanese Unexamined Patent Publication No. 6-31503 Japanese Patent Laid-Open No. 6-8010

In recent years, the performance of cutting machines has been remarkable. On the other hand, there is a strong demand for labor saving, energy saving, and cost reduction for cutting work, and along with this, cutting work tends to be further accelerated. For coated cermet tools, there is no problem when this is used for continuous cutting and interrupted cutting under normal conditions such as steel and cast iron. The Ti compound layer, which is the lower layer of the hard coating layer, has high strength and excellent impact resistance when used for high-speed intermittent cutting in which mechanical thermal shock is repeatedly applied at a very short pitch. The vapor deposited α-type Al ₂ O ₃ layer that constitutes the upper layer is excellent in high temperature hardness and heat resistance, but is extremely brittle against mechanical thermal shock. Is Ping (small chipping) is likely to occur, and as a result, the service life is reached in a relatively short time.

Therefore, as a result of conducting research to improve the chipping resistance of the Al ₂ O ₃ layer constituting the upper layer of the hard coating layer of the above coated cermet tool from the above viewpoint,
(A) As described above, the vapor-deposited α-type Al ₂ O ₃ layer as the hard coating layer is excellent in high-temperature hardness and heat resistance, but does not have sufficient high-temperature strength and exhibits satisfactory chipping resistance. On the other hand, an Al ₂ O ₃ layer having a κ-type or θ-type crystal structure in a vapor-deposited state has a relatively high high-temperature strength compared to the vapor-deposited α-type Al ₂ O ₃ layer. Although it exhibits excellent chipping resistance, it has inferior properties in terms of high temperature hardness and heat resistance.

(B) After forming the Ti compound layer as a lower layer under normal conditions on the surface of the tool base with a normal chemical vapor deposition apparatus, the κ-type or θ-type is formed under the same normal conditions. An Al ₂ O ₃ layer having the following crystal structure is formed, followed by heat treatment, desirably heat treatment in an Ar atmosphere at a pressure of 7 to 50 kPa, and a temperature of 1000 to 1200 ° C. for 5 to 80 minutes. However, the Ti compound layer does not change in the crystal structure, but the Al ₂ O ₃ layer having the κ-type or θ-type crystal structure is transformed into an α-type crystal structure Al ₂ O ₃ layer, During this transformation, a crack due to volume shrinkage occurs, and this transformation crack exists as a large crack in the α-type Al ₂ O ₃ layer after transformation, which causes chipping during cutting.

(C) Without subjecting the Al ₂ O ₃ layer having a κ-type or θ-type crystal structure to the surface of the Ti compound layer of (b) above, without performing heat treatment under the above conditions, In the same chemical vapor deposition system,
Reaction gas composition: by _{volume%, CrCl 3: 0.5~3%,} HCl: 0.5~3%, CO 2: 2~10%, H 2: remainder,
Reaction atmosphere temperature: 950 to 1050 ° C.
Reaction atmosphere pressure: 7 to 40 kPa,
To form a chromium oxide (hereinafter referred to as Cr ₃ O ₂ ) layer with an average layer thickness of 1.5 to 5 μm on the surface of the vapor-deposited κ-type or θ-type Al ₂ O ₃ layer, in this state, subjected to heat treatment under the conditions of the above (b), when the transforming the the Al ₂ O ₃ layer of the κ-type or θ-type crystal structure in the Al ₂ O ₃ layer of α-type crystal structure, wherein The Cr ₃ O ₂ layer formed on the surface of the Al ₂ O ₃ layer before transformation is accompanied by volume shrinkage due to transformation from the κ-type or θ-type crystal structure of the Al ₂ O ₃ layer to the α-type crystal structure. while significantly suppressed the development of cracks generated, the transformation acts to simultaneously start over the entire surface of the Al ₂ O ₃ layer, proceeds from the surface to the inside portion of the over time the Al ₂ O ₃ layer Therefore, the cracks that occur during transformation are extremely fine and distributed uniformly throughout the layer. In addition to the fabric state, very small even if the crystal orientation also changes the crystal orientation and equal to or crystal orientation having the κ-type or θ-type the Al ₂ O ₃ layer prior to transformation in the Al ₂ O ₃ layer after metamorphosis As a result, the heat-transformed α-type Al ₂ O ₃ layer formed has a high-temperature hardness and heat resistance with an α-type crystal structure, as well as a vaporized κ-type or θ-type Al ₂ O ₃ layer before the heat-transformation. Accordingly, the upper layer of the hard coating layer is the heat-transformed α-type Al ₂ O ₃ layer and the Cr ₃ O ₂ layer, and the lower layer is the Ti compound layer. In addition to the excellent high-temperature hardness and heat resistance, the heat-transformed α-type Al ₂ O ₃ layer is excellent even in high-speed interrupted cutting with severe mechanical and thermal shock. Because of its excellent chipping resistance, What coexistence coupled with the said Ti compound layer having a high temperature strength have, chipping in the hard coating layer is markedly suppressed, it exhibits a superior wear resistance over a long period.

(D) About the above-mentioned conventional vapor deposition α-type Al ₂ O ₃ layer and the heat-transformed α-type Al ₂ O ₃ layer of (c) above,
Using a field emission scanning electron microscope, as shown in the schematic explanatory diagrams in FIGS. 1A and 1B, an electron beam is individually applied to each crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polished surface. Irradiation is performed to measure the inclination angle formed by the normal line of the (0001) plane that is the crystal plane of the crystal grain with respect to the normal line of the surface-polished surface. When the measured inclination angle within the range is divided for each pitch of 0.25 degrees and the inclination angle number distribution graph is created by summing up the frequencies existing in each division, the conventional vapor deposition α-type Al ₂ As illustrated in FIG. 3, the O ₃ layer exhibits an unbiased inclination angle number distribution graph in the range of the measured inclination angle of the (0001) plane within the range of 0 to 45 degrees, whereas the heating transformation the α-type the Al ₂ O ₃ layer, sharp street, in a specific position of the tilt angle segment illustrated in FIG. 2 Appears high peak, the sharp highest peak, the position and height appear on the tilt angle sections of the graph the horizontal axis is changed by the changing the average layer thickness of Cr ₃ O ₂ layer.

(E) According to the test results, when the Cr ₃ O ₂ layer has an average layer thickness of 1.5 to 5 μm as described above, the sharp maximum peak is within the range of 2 to 12 degrees of the tilt angle section. A ratio of 45% or more of the total frequency in the gradient angle distribution graph that appears and the total frequency within the range of 2 to 12 degrees (the total frequency and the height of the highest peak are in a proportional relationship) An inclination angle number distribution graph occupying an angle of 2 is obtained. In the resulting inclination angle number distribution graph, the ratio of the inclination angle number within the range of 2 to 12 degrees occupies 45% or more, and the range of 2 to 12 degrees. The coated cermet tool formed by vapor deposition in the state of coexisting with the Ti compound layer of the lower layer, with the heat-transformed α-type Al ₂ O ₃ layer in which the highest peak of the inclination angle section appears as the upper layer of the hard coating layer, Compared to conventional coated cermet tools No particular chipping occurs cutting edge at high speed interrupted cutting, to become to exert more excellent wear resistance.
The research results shown in (a) to (e) 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) The lower layer is composed of one or more of TiC layer, TiN layer, TiCN layer, TiCO layer, and TiCNO layer formed by chemical vapor deposition, and has a total average layer thickness of 3 to 20 μm. A Ti compound layer having
(B) On the surface of the Al ₂ O ₃ layer having a kappa-type or θ-type crystal structure and an average layer thickness of 1 to 15 μm in a state where the upper layer is formed by chemical vapor deposition, a Cr ₃ O ₂ layer is added to the surface of 1.5 to In a state where chemical vapor deposition is formed with an average layer thickness of 5 μm, heat treatment is performed to transform the crystal structure of the Al ₂ O ₃ layer having the κ-type or θ-type crystal structure into an α-type crystal structure,
Using a field emission scanning electron microscope, each crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polishing surface is irradiated with an electron beam, and the crystal grain is compared with the normal line of the surface polishing surface. The tilt angle formed by the normal line of the (0001) plane, which is the crystal plane, is measured, and among the measured tilt angles, the measured tilt angles within the range of 0 to 45 degrees are classified for each pitch of 0.25 degrees. In addition, in the slope angle distribution graph obtained by counting the frequencies existing in each section, the highest peak exists in the slope angle section within the range of 2 to 12 degrees and also exists within the range of 2 to 12 degrees. A heat-transformed α-type Al ₂ O ₃ layer showing an inclination angle distribution graph in which the total frequency is 45% or more of the entire frequency in the inclination angle distribution graph,
The present invention is characterized by a coated cermet tool having the chipping resistance with excellent hard coating layer formed by forming the hard coating layer constituted by (a) and (b) above.

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) Average thickness of the Ti compound layer (lower layer) The Ti compound layer itself has a relatively high high-temperature strength as compared with the α-type Al ₂ O ₃ layer, and the hard coating layer due to its presence. In addition to having excellent high-temperature strength, it firmly adheres to both the tool base and the heat-transformed α-type Al ₂ O ₃ layer, which is the upper layer, thereby improving the adhesion of the hard coating layer to the tool base. Although it has a contributing effect, if the total average layer thickness is less than 3 μm, the above-mentioned effect cannot be fully exerted. On the other hand, if the total average layer thickness exceeds 20 μm, it is particularly high-speed intermittent with high heat generation. Since it becomes easy to cause thermoplastic deformation by cutting and this causes uneven wear, the total average layer thickness was determined to be 3 to 20 μm.

The average layer thickness Cr ₃ O ₂ layers of (b) Cr ₃ O ₂ layer, on heating transformation to heat transformation α type the Al ₂ O ₃ layer of the street deposition κ type or θ-type the Al ₂ O ₃ layer, while significantly suppressed the development of cracks generated is accompanied by volume contraction, the transformation simultaneously to start over the Al ₂ O ₃ layer on the whole surface and from the surface to the inside portion of the over time the Al ₂ O ₃ layer Since there is an action to take the transformation form to proceed, there is an action that the cracks generated during the heat transformation are refined and uniform over the entire layer, and the Cr ₃ O ₂ layer has an average layer thickness. Is 1.5 to 5 μm, according to the test results, the highest peak of the measured inclination angle appears in the inclination angle range of 2 to 12 degrees in the inclination angle number distribution graph, and the 2 The total ratio of the frequencies existing in the inclination angle section of -12 degrees is the inclination angle number distribution group. Has the effect of showing the inclination angle frequency distribution graph as a more than 45% of the total power at off, therefore, in the less than average layer thickness of 1.5, the inclination angle frequency distribution graph of the heating transformation α type the Al ₂ O ₃ layer The peak height appearing in the range of 2 to 12 degrees is insufficient, that is, the total ratio of the frequencies existing in the range of 2 to 12 degrees is less than 45% of the total degrees in the inclination angle frequency distribution graph. In this case, as described above, the heat-transformed α-type Al ₂ O ₃ layer cannot secure a desired excellent high-temperature strength, and as a result, a desired improvement effect in chipping resistance cannot be obtained. When the average layer thickness exceeds 5 μm, the inclination angle section where the highest peak appears is out of the range of 2 to 12 degrees. In this case, the heat transformed α-type Al ₂ O ₃ layer also has a desired excellent high temperature strength. Cannot be secured From, it determined the average layer thickness and 1.5～5Myuemu.

(C) Average layer thickness of vapor-deposited κ-type or θ-type Al ₂ O ₃ layer (upper layer) The vapor-deposited κ-type or θ-type Al ₂ O ₃ layer has excellent high-temperature hardness and heat resistance after heat transformation as described above. Inclination angle classification: Shows an inclination angle distribution graph in which the highest peak appears in the range of 2 to 12 degrees, and becomes a heat-transformed α-type Al ₂ O ₃ layer with excellent high-temperature strength, and chipping occurs even in high-speed intermittent cutting Excellent wear resistance, but if the average layer thickness is less than 1 μm, the desired wear resistance cannot be ensured, while if the average layer thickness exceeds 15 μm, the chipping will occur. Therefore, the average layer thickness was determined to be 1 to 15 μm.

  In addition, for the purpose of identification before and after the use of the cutting tool, a TiN layer having a golden color tone may be vapor-deposited as the outermost surface layer of the hard coating layer as necessary, but the average layer thickness in this case is It may be 0.1 to 1 μm, and if it 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 of the present invention has a mechanically high thermal shock, and the high temperature intermittent cutting of steel accompanied by high heat generation includes a heat-transformed α-type Al ₂ O ₃ layer constituting the upper layer of the hard coating layer. In addition to excellent high temperature hardness and heat resistance, it exhibits excellent chipping resistance, and therefore exhibits excellent wear resistance over a long period of time.

  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 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 the sintering, the cutting edge portion was subjected to a honing process of R: 0.07 mm. Tool bases a to f made of TiCN-based cermet having a standard / CNMG12041 chip shape were formed.

Next, an ordinary chemical vapor deposition apparatus is used on the surfaces of the tool bases A to F and the tool bases a to f, and Table 3 (l-TiCN in Table 3 is described in JP-A-6-8010). Ti compound as a lower layer of the hard coating layer under the conditions shown in (1) shows the conditions for forming a TiCN layer having a vertically grown crystal structure, and (2) shows conditions for forming a normal granular crystal structure. The layers are formed by vapor deposition in the combinations shown in Table 4 and with the target layer thickness. Then, under the conditions shown in Table 3, Al ₂ O ₃ layers having a crystal structure of κ type or θ type are also shown in Table 4. Vapor deposition is performed in the combination shown and with the target layer thickness, and then the Cr ₃ O ₂ layer is formed on the surface of the vapor-deposited κ-type or θ-type Al ₂ O ₃ layer under the same conditions as shown in Table 3. In a state of vapor deposition with a target layer thickness In an Ar atmosphere at 30kPa Les, temperature: 1100 ° C. and subjected to heat treatment at a predetermined time holding conditions in the range of 10 to 60 minutes, Al ₂ O ₃ layer of the deposition κ-type or θ-type crystal structure Were transformed into an Al ₂ O ₃ layer having an α-type crystal structure to form an upper layer as a heat-transformed α-type Al ₂ O ₃ layer, thereby producing the coated cermet tools 1 to 13 of the present invention.

For the purpose of comparison, as shown in Table 5, an evaporated α-type Al ₂ O ₃ layer having the target layer thickness shown in Table 5 is also formed as the upper layer of the hard coating layer under the same conditions as shown in Table 3. In addition, conventionally coated cermet tools 1 to 13 were produced under the same conditions except that the formation of the Cr ₃ O ₂ layer and the heat treatment under the above conditions were not performed.

Next, with respect to the heat-transformed α-type Al ₂ O ₃ layer and the vapor-deposited α-type Al ₂ O ₃ layer constituting the hard coating layer of the above-described coated cermet tool of the present invention and the conventional coated cermet tool, using a field emission scanning electron microscope The inclination angle number distribution graph was created respectively.
That is, the inclination angle number distribution graph shows the inside of the column of the field emission scanning electron microscope in a state where the surfaces of the heat-transformed α-type Al ₂ O ₃ layer and the vapor-deposited α-type Al ₂ O ₃ layer are polished surfaces. And irradiating the polished surface with an electron beam having an acceleration voltage of 15 kV at an incident angle of 70 degrees with an irradiation current of 1 nA on each crystal grain having a hexagonal crystal lattice existing within the measurement range of the polished surface. Then, using an electron backscatter diffraction image apparatus, a region of 30 × 50 μm at a spacing of 0.1 μm / step is a (0001) plane which is the crystal plane of the crystal grain with respect to the normal line of the polished surface The inclination angle formed by the normal line is measured, and based on the measurement result, among the measurement inclination angles, the measurement inclination angle within the range of 0 to 45 degrees is divided for each pitch of 0.25 degrees, Created by counting the frequencies that exist in each category .

In the inclination angle number distribution graphs of the various heat-transformed α-type Al ₂ O ₃ layers and vapor-deposited α-type Al ₂ O ₃ layers obtained as a result, the inclination angle division in which the (0001) plane shows the highest peak, and 2 to 12 Tables 4 and 5 show the ratio of the number of inclination angles existing in the inclination angle section within the range of degrees to the whole inclination angle distribution graph in the inclination angle number graph, respectively.

In the above-mentioned various inclination angle number distribution graphs, as shown in Tables 4 and 5, each of the heat-transformed α-type Al ₂ O ₃ layers of the coated cermet tool of the present invention has a distribution of measured inclination angles on the (0001) plane. An inclination angle number distribution graph in which the highest peak appears in the inclination angle section within the range of 2 to 12 degrees, and the ratio of the inclination angle numbers existing in the inclination angle section within the range of 2 to 12 degrees is 45% or more. In contrast, the vapor deposition α-type Al ₂ O ₃ layer of the conventional coated cermet tool is unbiased in the range of the measured inclination angle of the (0001) plane in the range of 0 to 45 degrees, and the highest peak is The inclination angle number distribution graph in which the ratio of the inclination angle number which does not exist and exists in the inclination angle section within the range of 2 to 12 degrees is also 25% or less was shown.
2 is an inclination angle distribution graph of the heat-transformed α-type Al ₂ O ₃ layer of the coated cermet tool 2 of the present invention, and FIG. 3 is an inclination angle of the vapor-deposited α-type Al ₂ O ₃ layer of the conventional coated cermet tool 2. Number distribution graphs are respectively shown.

In addition, for the coated cermet tools 1 to 13 of the present invention and the conventional coated cermet tools 1 to 13 obtained as a result, the constituent layers of the hard coating layer were measured with an Auger spectrometer (observation of the longitudinal section of the layer). In the former, it was confirmed that each of the layers consisted of a Ti compound layer having a composition substantially the same as the target composition, a heat-transformed α-type Al ₂ O ₃ layer, and a Cr ₃ O ₂ layer. On the other hand, it was confirmed that both of the latter consisted of a Ti compound having substantially the same composition as the target composition and a deposited α-type Al ₂ O ₃ layer.
Furthermore, when the thicknesses of the constituent layers of the hard coating layer of these coated cermet tools were measured using a scanning electron microscope (same longitudinal section measurement), all of them had an average layer thickness substantially equal to the target layer thickness (5 The average value of point measurement) was shown.

Next, in the state where each of the various coated cermet tools is screwed to the tip of the tool steel tool with a fixing jig, the present coated cermet tools 1 to 13 and the conventional coated cermet tools 1 to 13 are as follows.
Work material: JIS · SCM435 lengthwise equally spaced four round grooved round bars,
Cutting speed: 300 m / min,
Incision: 1.5mm,
Feed: 0.2mm / rev,
Cutting time: 10 minutes,
Dry high-speed intermittent cutting test (normal cutting speed is 200 m / min) of alloy steel under the above conditions (cutting condition A),
Work material: JIS / S50C lengthwise equal 4 round grooved round bars,
Cutting speed: 350 m / min,
Cutting depth: 2mm,
Feed: 0.3mm / rev,
Cutting time: 10 minutes,
Dry high-speed intermittent cutting test of carbon steel under the conditions (cutting condition B) (normal cutting speed is 250 m / min),
Work material: JIS / FCD600 lengthwise equal 4 round bars with longitudinal grooves,
Cutting speed: 350 m / min,
Incision: 2.5mm,
Feed: 0.2mm / rev,
Cutting time: 10 minutes,
The dry high-speed intermittent cutting test (normal cutting speed is 200 m / min) of ductile cast iron under the above conditions (cutting condition C), and the flank wear width of the cutting edge was measured in any cutting test. The measurement results are shown in Table 6.

From the results shown in Tables 4 to 6, in the coated cermet tools 1 to 13 of the present invention, the upper layer of the hard coating layer is an inclination angle section within the range of the inclination angle of the (0001) plane of 2 to 12 degrees. It is composed of a heated transformation α-type Al ₂ O ₃ layer showing the highest peak and showing an inclination angle number distribution graph in which the total ratio of the frequencies existing in the inclination angle division range of 2 to 12 degrees occupies 45% or more, The heat-transformed α-type Al ₂ O ₃ layer that forms the upper layer of the hard coating layer has excellent high-temperature hardness even in high-speed intermittent cutting of steel and cast iron with extremely high mechanical and thermal shock and high heat generation. In addition to exhibiting excellent chipping resistance in addition to heat resistance, the occurrence of chipping at the cutting edge is remarkably suppressed, and excellent wear resistance is exhibited, whereas the upper layer of the hard coating layer is ( The distribution of the measured inclination angle of the (0001) plane is 0 to 45 degrees. Unbiased manner and in囲内, in the conventional coated cermet tools 1 to 13, which is composed of vapor-deposited α-type the Al ₂ O ₃ layer showing the inclination angle frequency distribution graph in which the highest peak does not exist, the deposition α type with both high-speed intermittent cutting It is apparent that the Al ₂ O ₃ layer cannot withstand severe mechanical thermal shock, chipping occurs at the cutting edge, and the service life is reached in a relatively short time.

  As described above, the coated cermet tool of the present invention has extremely high mechanical thermal shock and high heat generation as well as continuous cutting and interrupted cutting under normal conditions such as various steels and cast iron. Because it exhibits excellent chipping resistance even in high-speed intermittent cutting with the most severe cutting conditions, and exhibits excellent cutting performance over a long period of time, it is possible to improve the performance of the cutting equipment and save labor and energy in cutting. Furthermore, it can cope with cost reduction sufficiently satisfactorily.

Is a schematic diagram illustrating a measurement range of the inclination angle of the crystal grains (0001) plane in various α type the Al ₂ O ₃ layer constituting the hard coating layer. It is an inclination angle number distribution graph of the (0001) plane of the heat-transformed α-type Al ₂ O ₃ layer constituting the hard coating layer of the coated cermet tool 2 of the present invention. It is an inclination angle number distribution graph of the (0001) plane of the vapor-deposited α-type Al ₂ O ₃ layer constituting the hard coating layer of the conventional coated cermet tool 2.

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 Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, and carbonitride oxide layer formed by chemical vapor deposition, And a Ti compound layer having a total average layer thickness of 3 to 20 μm,
(B) The upper layer is formed by chemical vapor deposition, and the chromium oxide layer is an average layer of 1.5 to 5 μm on the surface of an aluminum oxide layer having a κ-type or θ-type crystal structure and an average layer thickness of 1 to 15 μm. In a state where chemical vapor deposition is formed with a thickness, heat treatment is performed to transform the crystal structure of the aluminum oxide layer having the κ-type or θ-type crystal structure into an α-type crystal structure,
Using a field emission scanning electron microscope, each crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polishing surface is irradiated with an electron beam, and the crystal grain is compared with the normal line of the surface polishing surface. The tilt angle formed by the normal line of the (0001) plane, which is the crystal plane, is measured, and among the measured tilt angles, the measured tilt angles within the range of 0 to 45 degrees are divided for each pitch of 0.25 degrees. In addition, in the slope angle distribution graph obtained by counting the frequencies existing in each section, the highest peak exists in the slope angle section within the range of 2 to 12 degrees and also exists within the range of 2 to 12 degrees. A heat-transformed α-type aluminum oxide layer showing a tilt angle frequency distribution graph in which the total frequency to be measured occupies a ratio of 45% or more of the total frequency in the tilt angle frequency distribution graph,
A surface-coated cermet cutting tool having excellent chipping resistance due to the hard coating layer formed by the hard coating layer constituted of (a) and (b) above.

Images