JP4427731B2 - Cutting tool made of surface-coated cubic boron nitride-based sintered material that exhibits excellent chipping resistance and heat-resistant plastic deformation in high-speed intermittent cutting of hardened steel - Google Patents

Description

  In this invention, not only work materials such as normal steel and cast iron, but also various hardened steels such as carburized and hardened steel and heat-treated hardened steel are processed with extremely high heat generation and thermal Surface-coated cubic nitriding that provides excellent wear resistance over a long period of time without chipping (micro chipping) and thermoplastic deformation even in high-speed interrupted cutting conditions with extremely high mechanical impact The present invention relates to a cutting tool made of a boron-based sintered material (hereinafter referred to as a coated BN-based tool).

Conventionally, in general, on the surface of a base body (hereinafter referred to as a tool base body) made of cubic boron nitride-based sintered material,
(A) as the lower layer has an average layer thickness of 0.5 to 10 [mu] m, and the composition _{formula: (Ti 1-X Al X} ) N ( provided that an atomic ratio, X is 0.40 to 0.60 ),
A composite nitride of Ti and Al satisfying the following conditions (hereinafter referred to as (Ti, Al) N) layer:
(B) A vapor-deposited α-type aluminum oxide (hereinafter referred to as Al ₂ O ₃ ) layer having an α-type crystal structure in a vapor-deposited state and an average layer thickness of 0.5 to 10 μm as an upper layer ,
A coated BN-based tool formed by forming the hard coating layer configured as described above in (a) and (b) is known, and this coated BN-based tool is, for example, continuous cutting or intermittent cutting of various types of steel and cast iron. It is also known that it is used in
Japanese Patent Laid-Open No. 08-206902

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 BN-based tools, there is no problem when this is used for continuous cutting and intermittent cutting under normal conditions such as steel and cast iron, but various hardened steels such as carburized and hardened steel and heat-treated hardened steel. Is used for high-speed intermittent cutting with the severest cutting conditions, that is, high-speed intermittent cutting in which the hard coating layer is heated to a high temperature and repeated thermal mechanical impact is applied to the hard coating layer at a very short pitch. The (Ti, Al) N layer, which is the lower layer of the hard coating layer, has a relatively high high-temperature strength and excellent impact resistance, but it has uneven wear in high-speed cutting with high heat generation. Causative heat Susceptible to sexual deformation, deposited α-type the Al ₂ O ₃ layer constituting the same upper layer, although excellent high temperature hardness and heat resistance, relatively high-temperature strength is low, very against thermal mechanical impact Due to the brittleness, chipping easily occurs in the hard coating layer due to this, and as a result, the service life is reached in a relatively short time.

Therefore, from the above viewpoint, the present inventors focused on the hard coating layer of the above coated BN-based tool, and as a result of conducting research to improve chipping resistance and heat plastic deformation,
(A) Although the (Ti, Al) N layer as a conventional lower layer of the hard coating layer has a relatively high high temperature strength due to Ti as a constituent component and exhibits excellent impact resistance, the high temperature hardness by Al And because the heat resistance improvement effect is insufficient, high-speed cutting with high heat generation is likely to cause thermoplastic deformation that causes uneven wear, but this contains Si component,
_{Formula: [Ti 1- (X + Z} ) Al X Si Z] N ( provided that an atomic ratio, X is 0.40 to 0.60, Z represents a 0.01-0.10)
When the lower layer is composed of a composite nitride of Ti, Al, and Si [hereinafter referred to as (Ti, Al, Si) N] layer that satisfies the following conditions, the Si component in the (Ti, Al, Si) N layer is Al Coexistence with the heat resistance of the lower layer is remarkably improved, so that the lower layer is not thermoplastically deformed even when heated to a high temperature. Further, the Si component is subjected to a heat transformation treatment of the Al ₂ O ₃ layer in a later step. The lower layer (Ti, Al, Si) N layer is suppressed from thermal decomposition to TiN, AlN, etc., and thus the lower layer is stabilized after the heat transformation treatment, that is, a stable composite nitride layer, that is, (Ti, It has an action to exist as an Al, Si) N layer.

(B) As described above, the conventional 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. However, although it exhibits relatively excellent chipping resistance, it has inferior properties in terms of high temperature hardness and heat resistance.

(C) After forming the (Ti, Al, Si) N layer as a lower layer on the surface of the tool base using, for example, an arc ion plating apparatus which is a normal physical vapor deposition apparatus, a normal chemical vapor deposition apparatus is formed. Then, an Al ₂ O ₃ layer having a κ-type or θ-type crystal structure is formed in a vapor-deposited state under normal conditions, followed by heat treatment, preferably in an Ar atmosphere at a pressure of 7 to 50 kPa. When the heat treatment is performed at a temperature of 1000 to 1200 ° C. for 5 to 80 minutes, the (Ti, Al, Si) N layer is formed by vapor deposition without causing a decomposition reaction by the action of the Si component. While holding the remains, the the Al ₂ O ₃ layer having a κ-type or θ-type crystal structure is transformed into the Al ₂ O ₃ layer of α-type crystal structure, in this modification, cracking due to volume shrinkage (cracks) This transformation crack is the α after transformation. Present as large cracks in the Al ₂ O ₃ layer, it can cause chipping during cutting.

(D) The Al ₂ O ₃ layer having a κ-type or θ-type crystal structure in the state of being deposited on the surface of the (Ti, Al, Si) N layer of (c) is subjected to heat treatment under the above conditions. Without using the chemical vapor deposition equipment,
Reaction gas composition: by _{volume%, TiCl 4: 0.2~3%,} CO 2: 0.2~10%, Ar: 5~50%, H 2: remainder,
Reaction atmosphere temperature: 800-1100 ° C.
Reaction atmosphere pressure: 4 to 70 kPa,
Time: 15-60 minutes,
In this state, a titanium oxide (hereinafter referred to as TiO _X ) layer is formed with an average layer thickness of 0.05 to 1 μm on the surface of the vapor-deposited κ-type or θ-type Al ₂ O ₃ layer. in is subjected to a heat treatment under the conditions of the above (c), when the transforming the the Al ₂ O ₃ layer of the deposition κ-type or θ-type crystal structure in the Al ₂ O ₃ layer of α-type crystal structure, the transformation TiO _X layer formed on the surface of the front of the Al ₂ O ₃ layer, the transformation and acts to simultaneously start over the entire surface of the Al ₂ O ₃ layer, the over time the Al ₂ O ₃ layer Cracks that occur due to volume shrinkage due to transformation from the κ-type or θ-type crystal structure to the α-type crystal structure of the Al ₂ O ₃ layer because it takes a transformation form that proceeds from the surface to the inside. is, extremely fine, and in addition to a state of being uniformly dispersed distributed throughout the layer, the the Al ₂ O ₃ layer after metamorphosis Kicking equivalent crystal orientation having crystal orientation even κ type before transformation or θ type the Al ₂ O ₃ layer, or a change in crystal orientation becomes extremely small, the heating transformation α-type Al ₂ O This result formed _{The three} layers have excellent high-temperature strength equivalent to the high-temperature strength of κ-type or θ-type Al ₂ O ₃ layers before heat transformation as well as excellent high-temperature hardness and heat resistance of α-type crystal structure. Therefore, in the coated BN-based tool in which the upper layer of the hard coating layer is the heat-transformed α-type Al ₂ O ₃ layer and the lower layer is composed of the (Ti, Al, Si) N layer, the heat generation is particularly high. In addition to high-temperature hardness and heat resistance, the heat-transformed α-type Al ₂ O ₃ layer has excellent high-temperature strength even in high-speed intermittent cutting of high-hardness steel with intense thermal mechanical impact. From high temperature strength by Ti component, Al and Si composition In combination with the (Ti, Al, Si) N layer having excellent heat resistance depending on the minute, there is no occurrence of thermoplastic deformation in the hard coating layer due to high-temperature heating, and the hard coating layer is a thermal machine. There is no occurrence of chipping due to mechanical impact, and it shows excellent wear resistance over a long period of time.

(E) About the above-mentioned conventional vapor deposition α-type Al ₂ O ₃ layer and the above-mentioned heat-transformed α-type Al ₂ O ₃ layer of (d),
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 It appears high peak, the sharp highest peak changes that the position and height appear on the tilt angle sections of the graph the horizontal axis by changing the average layer thickness of the TiO _X layer.

(E) According to the test results, when the TiO _X layer has an average layer thickness of 0.05 to 1 μm as described above, the sharp maximum peak appears in the range of 0 to 10 degrees of the tilt angle section. The total of the frequencies existing in the range of 0 to 10 degrees (the total frequency and the height of the highest peak are in a proportional relationship) occupy a ratio of 45% or more of the total frequencies in the inclination angle frequency distribution graph. An inclination angle number distribution graph is shown. In the resulting inclination angle number distribution graph, the ratio of the inclination angle number in the range of 0 to 10 degrees occupies 45% or more, and the range of 0 to 10 degrees is included. Heat-transformed α-type Al ₂ O ₃ layer in which the highest peak of the inclination angle section appears is the upper layer of the hard coating layer, and the coated BN is formed by vapor deposition in the state of coexisting with the lower (Ti, Al, Si) N layer System tools compared to the above-mentioned conventional coated BN tools In particular, even high-speed interrupted cutting of high-hardness steel with high heat generation and severe thermal mechanical impact will exhibit even better wear resistance without chipping at the cutting edge.
The research results shown in (a) to (e) above were obtained.

This invention was made based on the above research results, and on the surface of the tool base,
(A) The lower layer has an average layer thickness of 0.5 to 10 μm, and
_{Formula: [Ti 1- (X + Z} ) Al X Si Z] N ( provided that an atomic ratio, X is 0.40 to 0.60, Z represents a 0.01-0.10)
(Ti, Al, Si) N layer satisfying
(B) A TiO _X layer of 0.05 to 1 μm is formed on the surface of an Al ₂ O ₃ layer having a κ-type or θ-type crystal structure and an average layer thickness of 0.5 to 10 μm as an upper layer. In the state of vapor deposition with an average layer thickness of, a 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, and field emission A scanning electron microscope is used to irradiate each crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polished surface with an electron beam, so that the crystal of the crystal grain is normal to the surface polished surface. Measuring the inclination angle formed by the normal line of the (0001) plane, and dividing the measurement inclination angle within the range of 0 to 45 degrees out of the measurement inclination angles for each pitch of 0.25 degrees; In the inclination angle number distribution graph obtained by counting the frequencies existing in each section, 0 The highest peak exists in the inclination angle section within the range of -10 degrees, and the total of the frequencies existing within the range of 0 to 10 degrees occupies a ratio of 45% or more of the entire degrees in the inclination angle frequency distribution graph. Heat transformation α-type Al ₂ O ₃ layer showing an inclination angle number distribution graph,
A coated BN system that forms a hard coating layer composed of the above (a) and (b) and exhibits excellent chipping resistance and heat-resistant plastic deformation by high-speed intermittent cutting of high-hardness steel. It has a feature in the tool.

Next, the reason why the constituent layers of the hard coating layer of the coated BN tool of the present invention are numerically limited as described above will be described below.
(A) (Ti, Al, Si) N layer (lower layer)
In the (Ti, Al, Si) N layer, as described above, Ti improves high-temperature strength, Al improves high-temperature hardness and heat resistance, and Si further increases heat resistance in the coexistence with Al. In addition to suppressing thermoplastic deformation, it prevents the (Ti, Al, Si) N layer from undergoing a decomposition reaction in the heat transformation treatment of the Al ₂ O ₃ layer, thus maintaining excellent chipping resistance. In this state, there is an effect of improving the heat-resistant plastic deformability. Therefore, when the X value indicating the Al content is less than 0.40 in the total amount of Ti and Si, a high hardness steel with high heat generation. In the high-speed cutting, the thermoplastic deformation that causes uneven wear is likely to occur. On the other hand, if the X value exceeds 0.60, the high-temperature strength rapidly decreases and chipping is likely to occur. Is defined as 0.40 to 0.60 .
Further, when the Z value indicating the Si content ratio is less than 0.01 in the total amount of Ti and Al, the desired heat resistant plastic deformation improvement effect and the lower layer during the heat transformation treatment of the Al ₂ O ₃ layer On the other hand, if the Z value exceeds 0.10, the high-temperature strength rapidly decreases and chipping is likely to occur. 10 was determined.
Further, when the average layer thickness is less than 0.5 μm, the above-mentioned characteristics of the (Ti, Al, Si) N layer cannot be sufficiently exhibited, while when the average layer thickness exceeds 10 μm Since chipping is likely to occur in the coating layer, the average layer thickness was determined to be 0.5 to 10 μm.

(B) TiO _X layer In the TiO _X layer, as described above, when the vaporized κ-type or θ-type Al ₂ O ₃ layer is transformed into a heat-transformed α-type Al ₂ O ₃ layer, the transformation is converted into an Al ₂ O ₃ layer. It has the effect of starting simultaneously over the entire surface and taking the transformation form that progresses from the surface of the Al ₂ O ₃ layer to the inside over time, so it occurs with volume shrinkage during heating transformation In addition to miniaturization and homogenization of cracks throughout the layer, the crystal orientation in the Al ₂ O ₃ layer after transformation is the same as that of the κ-type or θ-type Al ₂ O ₃ layer before transformation, or crystal orientation If the average thickness of the TiO _X layer is 0.05 to 1 μm, according to the test results, the slope angle distribution graph corresponds to this. Maximum measured tilt angle within 0-10 degree tilt range There is an effect of showing an inclination angle number distribution graph in which a peak appears and the total ratio of the frequencies existing in the inclination angle section of 0 to 10 degrees is 45% or more of the whole frequency in the inclination angle degree distribution graph. When the average layer thickness is less than 0.05, the peak height that appears in the range of 0 to 10 degrees in the gradient angle distribution graph of the heat-transformed α-type Al ₂ O ₃ layer is insufficient. The total ratio of the frequencies existing within the range of 10 degrees is less than 45% of the total frequencies in the inclination angle frequency distribution graph. In this case, as described above, the heating transformation α-type Al ₂ O ₃ layer has a desired ratio. The excellent high temperature strength cannot be secured, and as a result, the desired improvement effect in chipping resistance cannot be obtained. On the other hand, when the average layer thickness exceeds 1 μm, the inclination angle section where the highest peak appears is 0 to 10 degrees. Out of range In this case as well, since the desired excellent high-temperature strength cannot be ensured in the heat-transformed α-type Al ₂ O ₃ layer, the average layer thickness is set to 0.05 to 1 μm.

(C) Evaporated κ-type or θ-type Al ₂ O ₃ layer (upper layer)
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, and a tilt angle distribution graph in which the highest peak appears in the range of measured tilt angle: 0 to 10 degrees. It becomes a heat-transformed α-type Al ₂ O ₃ layer with excellent high-temperature strength, and it exhibits excellent wear resistance without occurrence of chipping even in high-speed intermittent cutting, but its average layer thickness is less than 0.5 μm In this case, the desired wear resistance cannot be ensured. On the other hand, if the average layer thickness exceeds 10 μm, chipping is likely to occur. Therefore, the average layer thickness is 0.5 to 10 μm. Determined.

  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 the thickness is less than 0.1 μm, a sufficient discrimination effect cannot be obtained, while the discrimination effect by the TiN layer is sufficient for an average layer thickness of up to 1 μm.

This invention coated BN-based tool performs cutting of various hardened steels such as carburized hardened steel and heat-treated hardened steel under high-speed intermittent cutting conditions with extremely high thermal mechanical impact and high heat generation. However, the heat-transformed α-type Al ₂ O ₃ layer that forms the upper layer of the hard coating layer has excellent high-temperature strength in addition to excellent high-temperature hardness and heat resistance, resulting in excellent chipping resistance. In addition, the (Ti, Al, Si) N layer, which is the lower layer, has excellent thermoplastic deformation properties in a state where high temperature strength is maintained, and therefore exhibits excellent wear resistance over a long period of time. It is.

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

As raw material powders, cubic boron nitride (hereinafter referred to as c-BN) powder, titanium carbide (hereinafter referred to as TiC) powder, titanium nitride (hereinafter referred to as “c-BN”) having an average particle diameter in the range of 0.4 to 5 μm. , TiN) powder, titanium carbonitride (hereinafter referred to as TiCN) powder, tungsten carbide (hereinafter referred to as WC) powder, Al powder, Co powder, Ti ₃ Al intermetallic compound powder Ti ₃ Al powder , TiAl powder, and TiAl ₃ powder, further composition formula: composite metal nitride powder having Ti ₂ AlN, TiB ₂ powder, aluminum nitride (hereinafter referred to as AlN) powder, aluminum boride (hereinafter referred to as AlB ₂ ) Powder and aluminum oxide (shown as Al ₂ O ₃ ) powder were prepared, these raw material powders were blended into the blending composition shown in Table 1, wet mixed for 95 hours with a ball mill, and dried. Then, it was press-molded into a green compact having a diameter of 50 mm × thickness: 1.5 mm at a pressure of 100 MPa, and this green compact was then subjected to a pressure range of 900 to 1300 ° C. in a vacuum atmosphere of 1 Pa. The pre-sintered body for cutting edge pieces was sintered under the condition of holding at a predetermined temperature for 60 minutes, and this pre-sintered body was prepared separately, Co: 8% by mass, WC: remaining composition, and diameter : 50 mm x thickness: WC based cemented carbide support piece having a dimension of 2 mm, and placed in a normal ultra high pressure sintering apparatus, pressure: 5 GPa, temperature: Super high pressure sintering at a predetermined temperature in the range of 1200 to 1400 ° C. under the condition of holding time: 0.8 hour, and after sintering, the upper and lower surfaces are polished with a diamond grindstone, and 3 mm on a side by a wire electric discharge machine. Divided into equilateral triangles, Co: 5% by mass, TaC : 5 mass%, WC: remaining composition and shape of CIS standard CNGA120412 (thickness: 4.76 mm × one side length: 12.7 mm) Each corner of an equilateral triangle was subjected to arc machining with a central angle of 80 ° The brazing part (corner part) of the WC-based cemented carbide chip main body with a material has a composition consisting of Cu: 30%, Zn: 28%, Ni: 2%, and Ag: the rest. After brazing using a brazing material of Ag alloy and processing the outer periphery to a predetermined dimension, the cutting edge portion is subjected to honing processing with a width of 0.12 mm and an angle of 35 °, and further subjected to final polishing, thereby performing ISO polishing CNGA120204. Tool bases A to M having the following chip shapes were manufactured.

(A) First, each of these tool bases A to M is subjected to ultrasonic cleaning in acetone and dried, and an arc ion plating apparatus which is a normal physical vapor deposition apparatus shown schematically in FIG. As a cathode electrode (evaporation source), three types of Ti-Al-Si alloy and Ti-Al alloy for forming a lower layer having various component compositions, and metal Ti for forming an adhesion improving layer were used. Wearing,
(B) First, while evacuating the inside of the apparatus and maintaining the vacuum at 0.5 Pa or less, the inside of the apparatus was heated to 350 ° C. with a heater, and then Ar gas was introduced into the apparatus to form an Ar atmosphere of 4 Pa. In this state, a DC pulse bias voltage of −700 V is applied to the tool base, and the tool base surface is cleaned by Ar bombardment.
(C) Subsequently, nitrogen gas is introduced as a reaction gas into the apparatus to form a reaction atmosphere of 2 Pa, a DC pulse bias voltage of −200 V is applied to the tool base, and the metal Ti and anode serving as the cathode electrode In a state where a current of 100 A is passed between the electrodes to generate an arc discharge, a TiN layer as an adhesion improving layer is deposited on the surface of the tool base with a target layer thickness of 1 μm,
(D) The atmosphere of nitrogen gas as a reaction gas in the apparatus is set to 3.5 Pa, the bias voltage applied to the tool base is lowered to -30 V, and the Ti—Al—Si alloy or Ti— of the cathode electrode is reduced. Arc coating is generated between each of the Al alloys and the anode electrode, and each of the surfaces of the tool bases A to M has a target composition and a target layer thickness shown in Tables 3 and 4, respectively. Forming a (Ti, Al, Si) N layer as a lower layer constituting a hard coating layer of a BN-based tool or a (Ti, Al) N layer as that of a conventional coated BN-based tool,
(E) Next, on the surface of the (Ti, Al, Si) N layer, which is the lower layer, an Al ₂ O ₃ layer having a crystal structure of κ type or θ type under the conditions shown in Table 2 is used. And a target layer thickness, and a TiO _X layer is formed on the surface of the vapor-deposited κ-type or θ-type Al ₂ O ₃ layer under the conditions shown in Table 2 and also in Table 3. In the state of vapor deposition with the target layer thickness shown in FIG. 1, the κ type is subjected to heat treatment in a 13 kPa Ar atmosphere at a temperature of 1075 ° C. for a predetermined time within a range of 10 to 60 minutes. or the present invention coated BN system by forming an upper layer made of a heat transformation α type the Al ₂ O ₃ layer a the Al ₂ O ₃ layer of θ-type crystal structure by transformation in the Al ₂ O ₃ layer of α-type crystal structure Each tool 1-13 is manufactured,
(F) Furthermore, on the surface of the (Ti, Al) N layer, which is the lower layer, as shown in Table 4, under the conditions shown in Table 2 as the upper layer of the hard coating layer, the targets also shown in Table 4 Conventionally coated BN-based tools 1 to 13 were produced by forming a deposited α-type Al ₂ O ₃ layer having a layer thickness.

As a result, field emission type scanning was performed on 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 BN tool of the present invention and the conventional coated BN tool. An inclination angle number distribution graph was created using an electron microscope.
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 0 to 10 Tables 3 and 4 show the ratio of the number of inclination angles existing in the inclination angle section within the degree range to the inclination angle number of the entire inclination angle number distribution graph, respectively.

In the above-mentioned various inclination angle distribution graphs, as shown in Tables 3 and 4, each of the heat-transformed α-type Al ₂ O ₃ layers of the coated BN tool of the present invention has a measured inclination angle of the (0001) plane. An inclination angle number distribution in which the highest peak appears in the inclination angle section within the range of 0 to 10 degrees and the ratio of the inclination angle numbers existing in the inclination angle section within the range of 0 to 10 degrees is 45% or more. In contrast to the graph, the vapor deposition α-Al ₂ O ₃ layer of the conventional coated BN-based tool is all unbiased in the range of the measured inclination angle of the (0001) plane within the range of 0 to 45 degrees. The inclination angle number distribution graph in which no peak is present and the ratio of the inclination angle number existing in the inclination angle section within the range of 0 to 10 degrees is 25% or less is shown.
2 is a graph showing the inclination angle distribution of the heat-transformed α-type Al ₂ O ₃ layer of the coated BN-based tool 9 according to the present invention, and FIG. 3 is a graph showing the deposition α-type Al ₂ O ₃ layer of the conventional coated BN-based tool 9. An inclination angle number distribution graph is shown, respectively.

Moreover, about the present invention coated BN type tools 1 to 13 and the conventional coated BN type tools 1 to 13 obtained as a result, the constituent layers of the hard coating layer were measured with an Auger spectroscopic analyzer (observation of the longitudinal section of the layer). As a result, it was confirmed that the former consisted of a (Ti, Al, Si) N layer having substantially the same composition as the target composition, a heat-transformed α-type Al ₂ O ₃ layer, and a TiO _X layer. On the other hand, it was confirmed that both of the latter consisted of a (Ti, Al) N layer and a vapor-deposited α-type Al ₂ O ₃ layer having the same composition as the target composition. Furthermore, when the thickness of the constituent layer of the hard coating layer of these coated BN-based tools was measured using a scanning electron microscope (same longitudinal section measurement), the average layer thickness substantially the same as the target layer thickness ( Average value of 5-point measurement) was shown.

Next, the coated BN tools 1 to 13 of the present invention and the conventional coated BN tools 1 to 13 and the conventional coated BN tools 1 to 13 in the state where each of the various coated BN tools is screwed to the tip of the tool steel tool with a fixing jig. For 13,
Work material: JIS / SUJ2 heat-treated hardened steel (surface hardness: HRC59) in the longitudinal direction with 6 equally spaced round bars,
Cutting speed: 235 m / min,
Cutting depth: 0.07mm,
Feed: 0.08mm / rev,
Cutting time: 10 minutes,
Dry high-speed intermittent cutting test (normal cutting speed is 120 m / min) of heat-treated hardened steel under the above conditions (cutting condition A),
Work material: JIS / SCr420 carburized and hardened steel (surface hardness: HRC55), 6 longitudinally spaced round bars with equal intervals in the length direction,
Cutting speed: 245 m / min,
Cutting depth: 0.08mm,
Feed: 0.06mm / rev,
Cutting time: 10 minutes,
Dry high-speed intermittent cutting test (normal cutting speed is 120 m / min) of carburized and quenched steel under the above conditions (cutting condition B),
Work material: JIS / SCM415 carburized hardened steel (surface hardness: HRC60) in the longitudinal direction with 6 equally spaced round bars,
Cutting speed: 225 m / min,
Cutting depth: 0.07mm,
Feed: 0.06mm / rev,
Cutting time: 10 minutes,
A dry high-speed intermittent cutting test (normal cutting speed is 120 m / min) of carburized and hardened steel 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 5.

From the results shown in Tables 3 to 5, according to the present invention coated BN-based tools 1 to 13, the upper layer of the hard coating layer has an inclination angle division in the range where the inclination angle of the (0001) plane is 0 to 10 degrees. In addition, it is composed of a heat-transformed α-type Al ₂ O ₃ layer showing an inclination angle number distribution graph in which the total ratio of frequencies existing in the 0 to 10 degree inclination angle range is 45% or more. In addition to the excellent high-temperature hardness and heat resistance inherent in the α-type Al ₂ O ₃ layer, the α-type Al ₂ O ₃ layer has an extremely excellent high-temperature strength, and the lower layer (Ti, Al, Si) N layer Combined with the excellent high-temperature strength and heat-resistant plastic deformability, even the high-speed intermittent cutting of the above-mentioned high-hardness steel with extremely high thermal mechanical impact and high heat generation, the thermoplastic coating does not deform No chipping and excellent chipping resistance The upper layer of the hard coating layer is unbiased within the range of the measured inclination angle of the (0001) plane within the range of 0 to 45 degrees, while the highest peak is exhibited. In the conventional coated BN-based tools 1 to 13 which are composed of a vapor-deposited α-type Al ₂ O ₃ layer showing an inclination angle number distribution graph that does not exist, and the lower layer is a (Ti, Al) N layer, Due to insufficient high-temperature strength of the deposited α-type Al ₂ O ₃ layer, it cannot withstand severe thermal mechanical shock, chipping occurs, and thermoplasticity is due to insufficient heat resistance of the (Ti, Al) N layer. It is clear that deformation also occurs and this results in a service life in a relatively short time.

  As described above, the coated BN tool of the present invention has extremely high thermal mechanical impact and high heat generation, as well as continuous cutting and intermittent cutting under various conditions such as various steels and cast iron. Even when performing high-speed interrupted cutting, especially when cutting various hardened steels such as carburized hardened steel and heat-treated hardened steel, it exhibits excellent chipping resistance and heat-resistant plastic deformation, resulting in excellent cutting over a long period of time. Since it exhibits the performance, it can sufficiently satisfy the high performance of the cutting device, the labor saving and energy saving of the cutting work, and the cost reduction.

It 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 BN tool 9 of the present invention. It is a gradient 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 BN-based tool 9. It is a schematic explanatory drawing of the normal arc ion plating apparatus used in forming the lower layer of the hard coating layer of a covering BN base tool.

Claims (1)

On the surface of the tool base made of cubic boron nitride-based sintered material,
(A) The lower layer has an average layer thickness of 0.5 to 10 μm, and
_{Formula: [Ti 1- (X + Z} ) Al X Si Z] N ( provided that an atomic ratio, X is 0.40 to 0.60, Z represents a 0.01-0.10)
Ti, Al and Si composite nitride layer satisfying
(B) As an upper layer, a titanium oxide layer having an average of 0.05 to 1 μm is formed on the surface of an aluminum oxide layer having a κ-type or θ-type crystal structure and an average layer thickness of 0.5 to 10 μm in a vapor-deposited state. The aluminum oxide layer having the κ-type or θ-type crystal structure is transformed into an α-type crystal structure by performing a heat treatment in a state where the layer is formed by vapor deposition, and a field emission scanning electron microscope Is used to irradiate each crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polished surface with an electron beam, and the crystal plane of the crystal grain with respect to the normal of the surface polished surface ( The tilt angle formed by the normal line of the (0001) plane is measured, and among the measured tilt angles, the measured tilt angles within a range of 0 to 45 degrees are divided into pitches of 0.25 degrees, and within each section Inclination angle frequency distribution group that aggregates the existing frequencies In this case, the highest peak exists in the inclination angle section within the range of 0 to 10 degrees, and the total of the frequencies existing within the range of 0 to 10 degrees is 45% or more of the entire degrees in the inclination angle frequency distribution graph. Heat transformation α-type aluminum oxide layer showing an inclination angle number distribution graph occupying a ratio of
Surface-coated cubes that exhibit excellent chipping resistance and heat-resistant plastic deformation by high-speed intermittent cutting of high-hardness steel formed by forming a hard coating layer composed of (a) and (b) above. Cutting tool made of crystalline boron nitride sintered material.

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