JP2007160497A - SURFACE COATED CUTTING TOOL MADE OF CERMET HAVING PROPERTY-MODIFIED ALPHA TYPE Al2O3 LAYER OF HARD COATING LAYER HAVING EXCELLENT CRYSTAL GRAIN INTERFACE STRENGTH - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface coated cermet cutting tool, with property-modified α-type Al<SB>2</SB>O<SB>3</SB>layer in a hard coating layer, having excellent crystal grain interface strength. <P>SOLUTION: The cutting tool of cermet comprises the hard coating layer comprising a lower layer of Ti compound layer and an upper layer of an α-type Al<SB>2</SB>O<SB>3</SB>layer, formed on the surface of a tool base member. A field emission type scanning electron microscope and an electron back-scattered diffraction image device are used to radiate an electronic beam to each crystal grain having a hexagonal crystal grid existing in a measurement range of a surface polished face, so that the angle of the normal line of each crystal face of the crystal grain to the normal line of the surface-polished face where they cross each other is measured. Based on the result of this measurement, faces (0001) and faces ä10-10} are selected, and among the selected faces (0001) and faces ä10-10}, the angle of the normal lines of the faces (0001) in the interface (by the unit of crystal grain interface) between adjoining crystal grains to each other and to the normal lines of faces ä10-10} where they cross each other is 15 deg. or less in crystal grain interface units in 45% or more of total crystal grain interface units in the reformed α-type Al<SB>2</SB>O<SB>3</SB>layer to compose the device. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

In the present invention, the modified α-type Al ₂ O ₃ layer constituting the upper layer of the hard coating layer has excellent crystal grain interface strength, and particularly has high viscosity, and the cutting tool surface portion during cutting High adhesion of hard coating layer, resulting in extremely high chipping resistance in high-speed cutting of difficult-to-cut materials such as mild steel, stainless steel, and high manganese steel. The present invention relates to a surface-coated cermet cutting tool (hereinafter referred to as a coated cermet tool) that exhibits excellent wear resistance 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) Ti carbide (hereinafter referred to as TiC) layer, nitride (hereinafter also referred to as TiN) layer, carbonitride (hereinafter referred to as TiCN) layer formed by chemical vapor deposition of the lower layers. A Ti compound having a total average layer thickness of 3 to 20 μm, consisting of one or more of carbon dioxide (hereinafter referred to as TiCO) layer and carbonitride oxide (hereinafter referred to as TiCNO) layer layer,
(B) an aluminum oxide layer having an average layer thickness of 2 to 20 μm and having an α-type crystal structure in a state of chemical vapor deposition (hereinafter referred to as a conventional α-type Al ₂ O ₃ layer);
A coated cermet tool formed by vapor-depositing the hard coating layer constituted by (a) and (b) above is known, and this coated cermet tool is used for cutting various general steels and ordinary cast irons, for example. It is well known that

Further, in the above-described coated cermet tool, the constituent layer of the hard coating layer generally has a granular crystal structure, and further, the TiCN layer constituting the Ti compound layer as the lower layer is intended to improve the strength of the layer itself. In a normal chemical vapor deposition apparatus, a gas mixture containing organic carbonitrides is used as a reaction gas, and it is formed by chemical vapor deposition at an intermediate temperature range of 700 to 950 ° C. so that it has a vertically grown crystal structure. It is also known to do.
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. In coated cermet tools, there is no problem when used for high-speed cutting of general steel such as low alloy steel and carbon steel, and ordinary cast iron such as gray cast iron. When used for high-speed cutting of difficult-to-cut materials such as high-manganese steel, the difficult-to-cut material itself has a high viscosity and has high adhesion to the hard coating layer on the surface of the cutting tool during cutting. The tendency, combined with the further increase due to the high heat generated during high-speed cutting, has extremely high cutting resistance, while the high-temperature strength of the conventional α-type Al ₂ O ₃ layer that constitutes the hard coating layer can withstand this. As a result, chipping (slight chipping) is likely to occur in the cutting edge portion, and the service life is reached in a relatively short time due to this.

In view of the above, the present inventors have focused on the conventional coated cermet tool in which the conventional α-type Al ₂ O ₃ layer constitutes the upper layer of the hard coating layer, and in particular, the conventional α-type Al ₂ O ₃ layer result to conducted research promote chipping resistance improving,
(A) The conventional α-type Al ₂ O ₃ layer as the hard coating layer of the conventional coated cermet tool is generally a normal chemical vapor deposition apparatus,
Reaction gas composition: volume%, AlCl ₃ : 2 to 4%, CO ₂ : 4 to 8%, HCl: 1 to 3%, H ₂ S: 0.05 to 0.2%, H ₂ : remaining,
Reaction atmosphere temperature: 1020 to 1050 ° C.
Reaction atmosphere pressure: 6 to 10 kPa,
The α-type Al ₂ O ₃ layer is formed by the same ordinary chemical vapor deposition apparatus, for example,
Reaction gas composition:% by volume, AlCl ₃ : 6 to 10%, CO ₂ : 4 to 8%, HCl: 3 to 5%, H ₂ S: 0.25 to 0.6%, H ₂ : remaining,
Reaction atmosphere temperature: 920 to 1000 ° C.
Reaction atmosphere pressure: 6 to 10 kPa,
When the α-type Al ₂ O ₃ layer (hereinafter referred to as a modified α-type Al ₂ O ₃ layer) formed as a result of vapor deposition under the following conditions, the α-type Al ₂ O ₃ layer itself has excellent high-temperature hardness. In addition to heat resistance, it should have a higher temperature strength than the conventional α-type Al ₂ O ₃ layer.

(B) Regarding the conventional α-type Al ₂ O ₃ layer and the modified α-type Al ₂ O ₃ layer, FIG. 1 shows a hexagonal crystal lattice of crystal grains constituting the α-type Al ₂ O ₃ layer, As shown schematically in schematic perspective view of the relationship of the surface polished surface of the α-type Al ₂ O ₃ layer, it exists within the measurement range of the surface polished surface using a field emission scanning electron microscope and an electron backscatter diffraction image apparatus. Each crystal grain having a hexagonal crystal lattice is irradiated with an electron beam, and the angle at which each normal line of each crystal plane of the crystal grain intersects the normal line of the surface polished surface is measured. The (0001) plane and the {10-10} plane, which are the constituent crystal planes of the grains, are selected, and, in the selected (0001) plane and {10-10} plane, the interfaces between adjacent grains (crystal grain interfaces) Normals of (0001) planes in units) and {10 If the calculated angle of intersection of the normal line among the 10} plane, the reforming α-type Al ₂ O ₃ layer intersects the normal line between the normal to each other and {10-10} plane of the (0001) plane angle In the conventional α-type Al ₂ O ₃ layer, the crystal grain interface unit occupies a ratio of 45% or more of the crystal grain interface unit of 15 degrees or less, The crystal grain interface unit whose angle between the normal lines and the normal lines of the {10-10} planes is 15 degrees or less indicates 25% or less of the total crystal grain interface units. This result shows that the conventional α-type Al ₂ O _The modified α-type Al ₂ O ₃ layer shows that the modified α-type Al ₂ O ₃ layer has a much higher crystal grain interface strength than the _three- layer structure. The high-temperature strength of the layer itself must be significantly improved.

(C) Therefore, in addition to excellent high temperature hardness and heat resistance, the modified α-type Al ₂ O ₃ layer having excellent high temperature strength is used as the upper layer of the hard coating layer, and the lower Ti compound layer At the same time, the coated cermet tool formed by vapor deposition on the surface of the tool base does not cause chipping in the hard coating layer even in the high-speed cutting of the above difficult-to-cut material, which has a particularly high cutting resistance. Providing excellent wear resistance over a long period of time.
The research results (a) to (c) have been obtained.

This invention was made based on the above research results, and on the surface of the tool base,
(A) As a lower layer, any one or two or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, and carbonitride layer formed by chemical vapor deposition are formed. And a Ti compound layer having a total average layer thickness of 3 to 20 μm,
(B) As an upper layer, a hexagonal crystal having an α-type crystal structure in the state of chemical vapor deposition and existing within the measurement range of the surface polished surface using a field emission scanning electron microscope and an electron backscatter diffraction image apparatus Each crystal grain having a lattice is irradiated with an electron beam, and an angle at which each normal line of each crystal plane of the crystal grain intersects with a normal line of the surface polished surface is measured. The (0001) plane and {10-10} plane which are crystal planes are selected, and further, in the selected (0001) plane and {10-10} plane, at the interface between adjacent crystal grains (crystal grain interface unit), respectively. When the angles at which the normals of the (0001) plane and the normals of the {10-10} plane intersect are obtained, the normals of the (0001) plane and the normals of the {10-10} plane intersect. Crystal with an angle of 15 degrees or less It shows the grain boundaries sequence interface unit accounts for 45% or more of the total grain surface units and modified α-type aluminum oxide layer having an average layer thickness of 2 to 20 [mu] m,
The modified α-type aluminum oxide layer of the hard coating layer formed by vapor-depositing the hard coating layer composed of the above (a) and (b) has excellent crystal grain interface strength, particularly high speed of difficult-to-cut materials. This is characterized by a coated cermet tool that exhibits excellent chipping resistance when a hard coating layer is cut.

The reason why the numerical values of the constituent layers of the hard coating layer of the coated cermet tool of the present invention are limited as described above will be described below.
(A) Ti compound layer (lower layer)
The Ti compound layer basically exists as a lower layer of the modified α-type Al ₂ O ₃ layer, which is the upper layer, and contributes to improving the high temperature strength of the hard coating layer by its excellent high temperature strength. It adheres firmly to both the tool base and the modified α-type Al ₂ O ₃ layer, and thus contributes to improving the adhesion of the hard coating layer to the tool base, but if the total average layer thickness is less than 3 μm If the total average layer thickness exceeds 20 μm, the high-speed cutting of difficult-to-cut materials with high heat generation is likely to cause thermoplastic deformation, which is a cause of uneven wear. Therefore, the total average layer thickness was determined to be 3 to 20 μm.

(B) modified α type the Al ₂ O ₃ layer (upper layer)
As described above, in the crystal grain interface arrangement, the angle between the normal lines of the (0001) planes and the normal lines of the {10-10} planes at the interface between adjacent crystal grains (crystal grain interface unit) is 15 degrees. It has been clarified based on many test results that when the following crystal grain interface units occupy a ratio of 45% or more of the total crystal grain interface units, the crystal grain interface strength is further improved. Therefore, when the upper limit of the angle at which each normal intersects is, for example, 16 degrees, or when the proportion of the crystal grain interface unit where the angle between each normal intersects is 15 degrees or less is less than 45% The desired excellent grain interface strength cannot be ensured, and when the above conditions are satisfied, the modified α-type Al ₂ O ₃ layer has the excellent high-temperature hardness of the α-type Al ₂ O ₃ itself and In addition to heat resistance, It comes to have a high temperature strength.
Also, if the average layer thickness is less than 2 μm, the above properties cannot be sufficiently provided in the hard coating layer. On the other hand, if the average layer thickness exceeds 20 μm, chipping particularly in high-speed cutting of difficult-to-cut materials. Therefore, the average layer thickness was determined to be 2 to 20 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 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.

In the coated cermet tool of the present invention, the modified α-type Al ₂ O ₃ layer constituting the upper layer of the hard coating layer is excellent in addition to the excellent high-temperature hardness and heat resistance of the α-type Al ₂ O ₃ itself. Combined with the excellent high-temperature strength of the lower Ti compound layer, which has high-temperature strength, even in the high-speed cutting of difficult-to-cut materials with high cutting resistance, the hard coating layer has no chipping and excellent resistance to damage. It exhibits wear and enables further extension of the service life.

  Next, the coated cermet 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 was blended in the blending composition shown in Table 1, and then added with wax, mixed in a ball mill for 24 hours in acetone, dried under reduced pressure, and then 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 F made of a WC-based cemented carbide having a throwaway tip shape specified in ISO · CNMG120408 were manufactured.

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

Then, each of these tool bases A to F and tool bases a to f 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. Under the conditions shown in Table 4), the Ti compound layer having the target layer thickness shown in Table 4 is deposited as a lower layer of the hard coating layer.
(B) Next, the reaction gas composition: volume%, AlCl ₃ : a predetermined amount within the range of 6 to 10%, CO ₂ : 6%, HCl: 4%, H ₂ S: 0.25 to 0.6 Predetermined amount% within range, H ₂ : remaining,
Reaction atmosphere temperature: 960 ° C.
Reaction atmosphere pressure: 8 kPa,
Also the target layer thickness shown in Table 4 in the condition, the present invention coated cermet tools 1 to 13 were prepared respectively by also depositing form the modified α type the Al ₂ O ₃ layer as an upper layer.

For comparison purposes, the conventional α-type Al ₂ O ₃ layer, which is the upper layer of the hard coating layer,
Reaction gas composition: volume%, AlCl ₃ : predetermined amount in the range of 2-4%, CO ₂ : 6%, HCl: 2%, H ₂ S: in the range of 0.05-0.2% Quantitative, H ₂ : remaining,
Reaction atmosphere temperature: 1030 ° C.
Reaction atmosphere pressure: 8 kPa,
The conventional coated cermet tools 1 to 13 were manufactured under the same conditions except that the target layer thicknesses as shown in Table 5 were used.

Subsequently, the modified α-type Al ₂ O ₃ layer and the conventional α-type Al ₂ O ₃ layer constituting the upper layer of the hard coating layer of the above-described coated cermet tool 1-13 of the present invention and the conventional coated cermet tool 1-13, Using a field emission scanning electron microscope and an electron backscatter diffraction image apparatus, the crystal grain interface arrangement was investigated.
That is, the conventional α-type the Al ₂ O ₃ layer of the modified α type the Al ₂ O ₃ layer and the conventional coated cermet tools 1-13 of the invention as described above coated cermet tools 1 to 13, first, the respective surface polished surface In this state, it is set in a lens barrel of a field emission scanning electron microscope, and an electron beam with an acceleration voltage of 15 kV at an incident angle of 70 degrees is applied to the surface polishing surface with an irradiation current of 1 nA on each surface polishing surface. Each crystal grain having a hexagonal crystal lattice existing in the measurement range is irradiated, and an electron backscatter diffraction image apparatus is used, and a region of 30 × 50 μm is separated at an interval of 0.1 μm / step. The angle at which each normal of the surface intersects the normal of the surface polished surface is measured, and from this measurement result, the (0001) plane and the {10-10} plane that are the constituent crystal planes of the crystal grains are selected, and Selected (0 In the (01) plane and {10-10} plane, the angles at which the normal lines of the (0001) plane and the normal lines of the {10-10} plane intersect each other at the interface between adjacent crystal grains (grain interface unit) The ratio of the crystal grain interface units whose angle between the normal lines of the (0001) planes and the normal lines of the {10-10} planes is 15 degrees or less to the total crystal grain interface units (hereinafter, the intersection angle is 15 degrees) The ratios of the following crystal grain interface units are calculated and are shown in Tables 4 and 5, respectively.

As shown in Tables 4 and 5, each of the modified α-type Al ₂ O ₃ layers of the coated cermet tools 1 to 13 of the present invention is a crystal having a crystal grain interface unit ratio of 45% or more with an intersection angle of 15 degrees or less. Whereas the conventional α-type Al ₂ O ₃ layer of the conventional coated cermet tools 1 to 13 shows a grain interface arrangement, the ratio of the crystal grain interface units with a crossing angle of 15 degrees or less is 25% or less. The sequence was shown.

  Moreover, when the thickness of the constituent layer of the hard coating layer of the present coated cermet tools 1 to 13 and the conventional coated cermet tools 1 to 13 obtained as a result was measured using a scanning electron microscope (longitudinal section measurement). , Each showed an average layer thickness (average value of 5-point measurement) substantially the same as the target layer thickness.

Next, for the various coated cermet tools of the present invention coated cermet tool 1-13 and the conventional coated cermet tool 1-13, all of them are screwed with a fixing jig to the tip of the tool steel tool,
Work material: JIS / SUS430 lengthwise equal 4 round bars with flutes,
Cutting speed: 250 m / min. ,
Cutting depth: 1.2mm,
Feed: 0.25 mm / rev. ,
Cutting time: 10 minutes,
Dry intermittent high-speed cutting test (normal cutting speed 150 m / min.) Of stainless steel under the following conditions (referred to as cutting conditions A),
Work material: JIS / S15C round bar,
Cutting speed: 400 m / min. ,
Incision: 1.5mm,
Feed: 0.28 mm / rev. ,
Cutting time: 10 minutes,
Dry continuous high-speed cutting test (normal cutting speed is 250 m / min.) Of mild steel under the following conditions (referred to as cutting conditions B),
Work material: JIS-SMn443 round bar with four equal grooves in the longitudinal direction,
Cutting speed: 250 m / min. ,
Incision: 1.5mm,
Feed: 0.22 mm / rev. ,
Cutting time: 10 minutes,
A dry intermittent high-speed cutting test (normal cutting speed is 150 m / min.) Of high manganese steel under the above conditions (referred to as 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, the coated cermet tools 1 to 13 of the present invention all have crystal grain interface units in which the modified α-type Al ₂ O ₃ layer, which is the upper layer of the hard coating layer, has an intersection angle of 15 degrees or less. As a result, the modified α-type Al ₂ O ₃ layer has not only excellent high-temperature hardness and heat resistance, but also excellent crystal grain interface strength, that is, excellent high-temperature. The conventional α type, which is the upper layer of the hard coating layer, shows excellent wear resistance without occurrence of chipping even at high-speed cutting of difficult-to-cut materials with extremely high cutting resistance. The proportion of crystal grain interface units having an intersection angle of 15 degrees or less in the crystal grain interface arrangement of the Al ₂ O ₃ layer is 25% or less. As a result, the conventional α-type Al ₂ O ₃ layer does not have a sufficiently high temperature strength. Conventionally coated cermet tool In 1 to 13, it is clear that chipping occurs in the hard coating layer by high-speed cutting of difficult-to-cut materials, and the service life is reached in a relatively short time.

  As described above, the coated cermet tool of the present invention has high viscosity in addition to high-speed cutting such as various types of steel and cast iron, and has a high viscosity with respect to the hard coating layer on the surface of the cutting tool at the time of cutting. Even with high-speed cutting of difficult-to-cut materials such as mild steel, stainless steel, and high-manganese steel, which have high adhesion and high cutting resistance as a result, it exhibits excellent wear resistance without chipping. Since it exhibits excellent cutting 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.

a hexagonal crystal lattice with crystal grains constituting the α-type the Al ₂ O ₃ layer, the surface polishing plane relationship of the α-type Al ₂ O ₃ layer which is the schematic perspective view schematically showing.

Claims (1)

On the surface of the tool base composed of tungsten carbide based cemented carbide or titanium carbonitride based cermet,
(A) As a lower layer, any one or two or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, and carbonitride layer formed by chemical vapor deposition are formed. And a Ti compound layer having a total average layer thickness of 3 to 20 μm,
(B) As an upper layer, a hexagonal crystal having an α-type crystal structure in the state of chemical vapor deposition and existing within the measurement range of the surface polished surface using a field emission scanning electron microscope and an electron backscatter diffraction image apparatus Each crystal grain having a lattice is irradiated with an electron beam, and an angle at which each normal line of each crystal plane of the crystal grain intersects with a normal line of the surface polished surface is measured. The (0001) plane and {10-10} plane which are crystal planes are selected, and further, in the selected (0001) plane and {10-10} plane, at the interface between adjacent crystal grains (crystal grain interface unit), respectively. When the angles at which the normals of the (0001) plane and the normals of the {10-10} plane intersect are obtained, the normals of the (0001) plane and the normals of the {10-10} plane intersect. Crystal with an angle of 15 degrees or less It shows the grain boundaries sequence interface unit accounts for 45% or more of the total grain surface units and modified α-type aluminum oxide layer having an average layer thickness of 2 to 20 [mu] m,
A surface-coated cermet cutting tool having a crystal grain interface strength with a modified α-type aluminum oxide layer of the hard coating layer formed by vapor-depositing the hard coating layer composed of (a) and (b) above.

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