JP4706911B2 - Surface-coated cemented carbide cutting tool with excellent wear resistance due to high-speed gear cutting of alloy steel - Google Patents

Description

  The present invention provides a hard coating layer having excellent heat-resistant plastic deformation properties, and also having high-temperature hardness and high-temperature strength, and therefore, particularly when used for high-speed gear cutting with high heat generation such as alloy steel. However, there is no occurrence of thermoplastic deformation that causes uneven wear that accelerates the progress of wear in the hard coating layer, and as a result, a surface-coated cemented carbide gear cutting tool (hereinafter, referred to as excellent wear resistance) is exhibited. This is related to a coated carbide gear cutting tool.

Conventionally, various gears are generally used as structural members for automobiles, aircrafts, and various drive devices, and coated carbide gear cutting tools (solid hobs) are used for gear cutting of gear teeth.

Further, as the coated carbide gear cutting tool, for example, as shown in a schematic perspective view in FIG. 3, a plurality of tooth grooves are formed radially with respect to the rotation axis and along the length direction. Between the front and rear surfaces that face the tooth gap and the front surface is a rake face with respect to the rotation direction, and the tooth is composed of a top surface (tooth tip tooth surface) and both side surfaces (left and right tooth surfaces) that are flank surfaces Various hard parts are formed on the surface of a tungsten carbide based cemented carbide cutting tool body (hereinafter referred to as a carbide cutting base) machined into a shape in which a plurality of parts are continuously formed along the length direction. A coated carbide gear cutting tool formed by physical vapor deposition of a coating layer is known.

On the other hand, as a hard coating layer of a cutting tool made of a surface-coated cemented carbide such as a normal throwaway tip, end mill, and drill, for example,

_{Formula: [Ti 1- (X + Y} ) Al X Cr Y] N ( provided that an atomic ratio, X is 0.45 to 0.65, Y represents a 0.01 to 0.15),

It is known to form a hard coating layer composed of a composite nitride of Ti, Al, and Cr [hereinafter referred to as (Ti, Al, Cr) N] satisfying the requirements with an average layer thickness of 2 to 8 μm. Furthermore, the (Ti, Al, Cr) N layer constituting the hard coating layer is improved in high-temperature hardness and high-temperature oxidation resistance by Al as a constituent component, high-temperature strength by Ti, and heat resistance by Cr. It is also known to have properties.

Furthermore, the above-mentioned coated carbide cutting tool provided with the above-mentioned hard coating layer is obtained by, for example, applying the above-mentioned carbide cutting base to an arc ion plating apparatus which is a kind of physical vapor deposition apparatus schematically shown in FIG. For example, between the anode electrode and the cathode electrode (evaporation source) in which a Ti—Al—Cr alloy having a predetermined composition is set in a state where the inside of the apparatus is heated to a temperature of, for example, 500 ° C. with a heater, Arc discharge was generated under the condition of current: 90 A, and simultaneously nitrogen gas was introduced into the apparatus as a reaction gas to form a reaction atmosphere of, for example, 2 Pa. On the other hand, a bias voltage of, for example, −100 V was applied to the substrate. It is also known that it is produced by vapor-depositing a hard coating layer comprising the (Ti, Al, Cr) N layer on the surface of the substrate.
JP-A-7-237010

  In recent years, the performance of cutting devices has been dramatically improved. On the other hand, there is a strong demand for labor saving and energy saving and further cost reduction for cutting, and with this, cutting tends to be faster. In the coated carbide gear cutting tool, there is no problem when this is used under normal gear cutting conditions, but when this is used under high speed gear cutting conditions such as alloy steel with high heat generation, Since the hard coating layer takes the form of uneven wear due to the thermoplastic deformation, the wear progresses rapidly, and as a result, the wear life is reached in a relatively short time.

In view of the above, the present inventors have developed the above-described conventional cemented carbide cutting tool that exhibits excellent wear resistance with a hard coating layer particularly in high-speed gear cutting of alloy steel. As a result of conducting research by paying attention to the (Ti, Al, Cr) N layer that constitutes the hard coating layer of the coated carbide gear cutting tool,
(A) In the (Ti, Al, Cr) N layer constituting the hard coating layer, if the Cr component content is increased, the heat-resistant plastic deformation is improved, but the conventional (Ti, Al, Cr) N layer described above The Cr content of about 1 to 15 atomic% in the steel is not sufficient to prevent the occurrence of thermoplastic deformation in high-speed gear cutting with high heat generation of the alloy steel. In order to satisfy these requirements satisfactorily, Although it is necessary to contain 40-60 atomic% of Cr far exceeding -15 atomic%, a (Ti, Al, Cr) N layer containing 40-60 atomic% of Cr component is practically used as a hard coating layer. In order to provide it, it is necessary to contain a predetermined amount of Ti to ensure a predetermined high-temperature strength. As a result, the content ratio of the Al component becomes very small. As a result, the high-temperature hardness of the hard coating layer is extremely low. To be low.

(B) the composition _{formula: [Ti 1- (A + B} ) Al A Cr B] N ( provided that an atomic ratio, A is 0.01 to 0.10, B represents a 0.40 to 0.60) satisfies A (Ti, Al, Cr) N layer having a Cr content of 40 to 60 atomic%;
_{Formula: [Ti 1- (C + D} ) Al C Cr D] N ( provided that an atomic ratio, C is 0.20 to 0.35, D represents a 0.15 to 0.30) satisfies, relative (Ti, Al, Cr) N layer with a large content ratio of Al component,
Are alternately laminated in a state where each layer has an average layer thickness of 5 to 20 nm (nanometers), and this (Ti, Al, Cr) N layer is formed by the above-described alternate lamination structure of thin layers. The excellent heat-resistant plastic deformation property of the (Ti, Al, Cr) N layer (hereinafter referred to as the thin layer A) containing high Cr, the Cr content ratio being lower than that of the thin layer A, and relatively high A relatively high high temperature hardness of an Al-containing (Ti, Al, Cr) N layer (hereinafter referred to as a thin layer B).

(C) The (Ti, Al, Cr) N layer having the alternately laminated structure of the thin layer A and the thin layer B of (b) is excellent in heat plastic deformation required for high-speed gear cutting of alloy steel. Although it has a predetermined high temperature hardness, it can not be said that it has a sufficiently satisfactory high temperature hardness, so this is provided as the upper layer of the hard coating layer, while as the lower layer, the heat resistance plastic deformation is (Ti, Al, Cr) N layer having a composition corresponding to the above conventional hard coating layer, which is insufficient but has a relatively high content of Al component and has excellent high temperature hardness,
_{Formula: [Ti 1- (E + F} ) Al E Cr F] N ( provided that an atomic ratio, E is 0.45 to 0.65, F represents a 0.01 to 0.15) satisfies the single (Ti, Al, Cr) N layer of single phase structure,
Therefore, the resulting hard coating layer has all of excellent heat plastic deformation, high temperature strength, and high temperature hardness. Therefore, the hard coating layer is formed by vapor deposition of this hard coating layer. Carbide hobbing tools are superior in that high-speed gear cutting of alloy steel with high heat generation eliminates the occurrence of thermoplastic deformation that causes uneven wear in the hard coating layer and assumes a normal wear form. The wear resistance should be demonstrated over a long period of time.
The research results shown in (a) to (c) above were obtained.

The present invention has been made on the basis of the above research results, and a plurality of tooth spaces are formed radially and along the length direction with respect to the rotation axis. The tooth part that consists of the front and rear faces that face the groove and the front face is a rake face with respect to the rotation direction, and the top face (tooth tip tooth face) and both side faces (left and right tooth faces) that are flank faces On the surface of the tungsten carbide based cemented carbide cutting tool base having a shape formed continuously along the direction,
(A) Both are composed of an upper layer and a lower layer made of (Ti, Al, Cr) N, the upper layer has a layer thickness of 0.5 to 1.5 μm, and the lower layer has a layer thickness of 2 to 6 μm. ,
(B) Each of the upper layers has an alternate laminated structure of thin layers A and B having a layer thickness of 5 to 20 nm (nanometer),
The thin layer A is
Composition formula: [Ti _{1 − (A + B)} Al _A Cr _B ] N (wherein A represents 0.01 to 0.10 and B represents 0.40 to 0.60 in terms of atomic ratio) (Ti , Al, Cr) N layer,
The thin layer B is
Composition formula: [Ti _{1− (C + D)} Al _C Cr _D ] N (wherein C is 0.20 to 0.35 and D is 0.15 to 0.30 in atomic ratio) (Ti , Al, Cr) N layer,
(C) the lower layer has a single phase structure;
Composition formula: [Ti _{1− (E + F)} Al _E Cr _F ] N (wherein E is 0.45 to 0.65 and F is 0.01 to 0.15 in atomic ratio) (Ti , Al, Cr) N layer,
For the coated carbide cutting tool (surface coated cemented carbide cutting tool) that exhibits excellent wear resistance in high-speed gear cutting of alloy steel, formed by vapor-depositing a hard coating layer consisting of It has characteristics.

Next, regarding the hard coating layer of the coated carbide gear cutting tool of the present invention, the reason why the numerical values are limited as described above will be described.
(A) Composition formula and layer thickness of the lower layer As described above, the Al component in the (Ti, Al, Cr) N layer constituting the hard coating layer improves high temperature hardness, while the Ti component has high temperature strength. In addition, the Cr component has the effect of improving the heat-resistant plastic deformation, and the lower layer has a relatively high Al component content to provide a high high-temperature hardness. When the value is less than 0.45 in the ratio of the total amount of Ti and Cr (atomic ratio, the same applies hereinafter), the ratio of Ti is relatively increased, which is an excellent requirement for high-speed gear cutting of alloy steel. High temperature hardness cannot be ensured, and the progress of wear is accelerated rapidly. On the other hand, when the E value indicating the Al ratio exceeds 0.65, the Ti ratio is relatively decreased. , High-temperature strength drops rapidly, resulting in chipping (slight chipping) Therefore, the E value is set to 0.45 to 0.65.
Further, if the F value indicating the ratio of Cr is the ratio of the total amount of Ti and Al, and less than 0.01, the predetermined minimum heat-resistant plastic deformation cannot be ensured, while the F value is 0. If it exceeds .15, it becomes difficult to ensure a predetermined high-temperature strength, so the F value was determined to be 0.01 to 0.15.
Further, if the layer thickness is less than 2 μm, the excellent high-temperature hardness cannot be imparted to the hard coating layer over a long period of time, resulting in a short tool life. On the other hand, if the layer thickness exceeds 6 μm, chipping occurs. The layer thickness was determined to be 2 to 6 μm because it easily occurs.

(B) Composition formula of upper layer thin layer A The Cr component in (Ti, Al, Cr) N of the upper layer thin layer A has a relatively high content ratio as described above, and an alloy with high heat generation. It is included for the purpose of improving the heat-resistant plastic deformability in high-speed gear cutting of steel. Therefore, if the B value is less than 0.40, the desired excellent heat-resistant plastic deformability cannot be ensured. If the B value exceeds 0.60, even if a thin layer B having excellent high temperature strength is present adjacently, a decrease in high temperature strength of the upper layer is unavoidable and causes chipping. It was set to 0.40 to 0.60.
Further, the A value indicating the proportion of Al is the proportion of the total amount of Ti and Cr, and if it is less than 0.01, the minimum high-temperature hardness cannot be ensured, causing wear promotion, while the same A When the value exceeds 0.10, a tendency to decrease in the high-temperature strength appears and causes chipping, so the A value was determined to be 0.01 to 0.10.

(C) Composition formula of thin layer B of the upper layer In the thin layer B of the upper layer, the content ratio of the Cr component is relatively lower than that of the thin layer A, while the content ratio of the Al component is relatively By maintaining the high temperature hardness relatively high, the shortage of the high temperature hardness of the adjacent thin layer A is reinforced, so that the thin layer A has excellent heat-resistant plastic deformation and the thin layer The upper layer having a predetermined high-temperature hardness of B is formed. When the C value indicating the Al content in the composition formula of the thin layer B is less than 0.20, the Al content is It becomes too small to secure a predetermined high-temperature hardness, and the progress of wear of the hard coating layer is promoted. On the other hand, if the C value exceeds 0.35, the Ti component is relatively contained. Since the ratio decreases, a decrease in high-temperature strength is inevitable, causing chipping, The C value was determined to be 0.20 to 0.35.
Further, if the D value indicating the ratio of Cr is the ratio of the total amount of Ti and Al, and less than 0.15, the effect of improving the heat plastic deformation property of the entire upper layer is small, while the D value is 0.30. Since the high temperature strength of the whole upper layer will fall when exceeding, D value was defined as 0.15-0.30.

(D) Layer thicknesses of upper layer thin layer A and layer B If each layer thickness is less than 5 nm, it is difficult to form each thin layer clearly with the above composition. Excellent heat-resistant plastic deformation and predetermined high-temperature hardness cannot be ensured, and if each layer thickness exceeds 20 nm, each thin layer has a defect, ie, if it is thin layer A, high-temperature hardness is insufficient. In the case of the thin layer B, the lack of heat-resistant plastic deformability appears locally in the layer, and this makes it easier for chipping to occur or promotes the progress of wear. It was determined to be 5 to 20 nm.

(E) Layer thickness of the upper layer If the layer thickness is less than 0.5 μm, the excellent thermal plastic deformation property of itself cannot be imparted to the hard coating layer over a long period of time, resulting in a short tool life. If the thickness exceeds 1.5 μm, chipping is likely to occur. Therefore, the layer thickness is set to 0.5 to 1.5 μm.

  In the coated carbide gear cutting tool of the present invention, the hard coating layer is composed of a (Ti, Al, Cr) N layer, and the upper layer of the hard coating layer is formed by alternately laminating a thin layer A and a thin layer B. Because it has excellent heat-resistant plastic deformation and the lower layer of the single phase structure has excellent high-temperature hardness, even in high-speed gear cutting of alloy steel with high heat generation, thermoplastic deformation of the hard coating layer Is remarkably suppressed, and excellent wear resistance is exhibited over a long period of time.

Next, the coated carbide gear cutting 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 are blended in the composition shown in Table 1, wet mixed by a ball mill for 72 hours, dried, and then pressed into a green compact at a pressure of 100 MPa. Medium, sintered at 1400 ° C. for 1 hour to form a cemented carbide round bar material of diameter: 85 mm × length: 125 mm, and machined from this material, outer diameter: 80 mm X Length: Solid hob type cemented carbide cutting bases A to J shown in FIG. 3 each having a total dimension of 120 mm and a shape of two right-hand twists x 16 grooves were manufactured.

(A) Next, each of the above-mentioned superhard gear cutting bases A to J is ultrasonically cleaned in acetone and dried, and the central axis on the rotary table in the arc ion plating apparatus shown in FIG. A thin layer of an upper layer having a component composition corresponding to the target composition shown in Table 2 as a cathode electrode (evaporation source) on one side, mounted along a peripheral portion at a predetermined distance in the radial direction from Ti-Al-Cr alloy for forming A, Ti-Al- for forming thin layer B of the upper layer having the component composition corresponding to the target composition shown in Table 2 as the cathode electrode (evaporation source) on the other side A Cr alloy is disposed oppositely across the turntable, and Ti-Al- for forming a lower layer as a cathode electrode (evaporation source) along the turntable at a position shifted by 90 degrees from both the Ti-Al-Cr alloys. Cr The gold is attached,

(B) First, the inside of the apparatus is evacuated and kept at a vacuum of 0.1 Pa or less, the interior of the apparatus is heated to 500 ° C. with a heater, and then rotated onto the rotating table while rotating on the rotating table. A DC bias voltage of −1000 V is applied, and a current of 100 A is passed between the lower layer forming Ti—Al—Cr alloy and the anode electrode to generate an arc discharge. Bombard cleaning with Ti-Al-Cr alloy,
(C) Introducing nitrogen gas as a reaction gas into the apparatus to make a reaction atmosphere of 3 Pa, applying a DC bias voltage of −100 V to the carbide cutting base rotating while rotating on the rotary table, and An arc discharge is generated by passing a current of 100 A between the Ti—Al—Cr alloy for forming the lower layer and the anode electrode, so that the target composition and target shown in Table 2 are formed on the surface of the cemented carbide cutting base. (Ti, Al, Cr) N layer having a single-phase structure of layer thickness is deposited as a lower layer of the hard coating layer,
(D) Next, nitrogen gas was introduced as a reaction gas into the apparatus to make a reaction atmosphere of 2 Pa, and a DC bias voltage of −100 V was applied to the carbide cutting base rotating while rotating on the rotary table. In this state, a predetermined current in a range of 50 to 200 A is passed between the cathode electrode and the anode electrode of the Ti-Al-Cr alloy for forming the thin layer A to generate arc discharge, and the cemented carbide cutting A thin layer A having a predetermined thickness is formed on the surface of the substrate, and after the thin layer A is formed, the arc discharge is stopped, and instead, between the cathode electrode and the anode electrode of the Ti-Al-Cr alloy for forming the thin layer B Similarly, a predetermined current in the range of 50 to 200 A is supplied to generate arc discharge to form a thin layer B having a predetermined thickness, and then the arc discharge is stopped (in this case, starting from the formation of the thin layer B). The thin layer A type Of thin layer A by arc discharge between cathode electrode and anode electrode of Ti-Al-Cr alloy for use, and thin layer by arc discharge between cathode electrode and anode electrode of Ti-Al-Cr alloy for formation of thin layer B The formation of B is alternately repeated so that the target composition shown in Table 2 along the layer thickness direction and the thin layer A and the thin layer B having a single target layer thickness are alternately laminated on the surface of the cemented carbide cutting base. Similarly, the coated superhard gear cutting tools 1 to 10 of the present invention were manufactured by vapor-depositing the upper layers to be formed with the overall target layer thicknesses shown in Table 2, respectively.

Further, for the purpose of comparison, the above-described superhard gear cutting bases A to J are ultrasonically cleaned in acetone and dried, and then loaded into the arc ion plating apparatus shown in FIG. As the (evaporation source), a Ti—Al—Cr alloy having a component composition corresponding to the target composition shown in Table 3 is mounted, and the apparatus is first evacuated and kept at a vacuum of 0.1 Pa or less. Then, after heating the inside of the apparatus to 500 ° C. with a heater, a DC bias voltage of −1000 V was applied to the cemented carbide cutting base, and 100 A of the cathode electrode was placed between the Ti—Al—Cr alloy and the anode electrode. An electric current is applied to generate an arc discharge, so that the surface of the cemented carbide cutting substrate is bombarded with the Ti—Al—Cr alloy, and then nitrogen gas is introduced into the apparatus as a reaction gas to obtain a reaction atmosphere of 3 Pa. In addition, the bias voltage applied to the cemented carbide cutting base is lowered to −100 V to generate an arc discharge between the cathode electrode and the anode electrode of the Ti—Al—Cr alloy. A comparative coated carbide gear cutting tool is formed by vapor-depositing a hard coating layer consisting of a (Ti, Al, Cr) N layer having a single phase structure with the target composition and target layer thickness shown in Table 3 on the surface of 1 to 10 were produced.

Next, using the above-described coated carbide cutting tool 1-10 of the present invention and the comparative coated carbide cutting tool 1-10, the material is alloy steel of JIS / SCr420H,

Module: 2.0, pressure angle: 20 degrees, number of teeth: 29, twist angle: 25 degrees right-hand twist, tooth width: machining of gears with dimensions and shapes of 20.0 mm,

Cutting speed (rotational speed): 450 m / min,
Feed: 1.8mm / rev,
Processing form: climb, no shift, dry (air blow),
The high-speed gear cutting conditions (the cutting speed in the case of machining the above-mentioned JIS / SCr420H alloy steel gear is usually 350 m / min),
The number of gears processed until the flank wear width reached 0.1 mm was measured.
The measurement results are shown in Tables 2 and 3, respectively.

As a result, the thin layer A and the thin layer B of the hard coating layer made of (Ti, Al, Cr) N of the coated carbide cutting tool 1 to 10 of the present invention obtained, and the composition of the lower layer. The composition of the hard coating layer made of (Ti, Al, Cr) N of the comparative coated carbide gear cutting tools 1 to 10 was measured by energy dispersive X-ray analysis using a transmission electron microscope. Each showed substantially the same composition as the target composition.

Further, when the average layer thickness of the constituent layers of the hard coating layer was subjected to cross-sectional measurement using a transmission electron microscope, all showed the same average value (average value of five locations) as the target layer thickness.

From the results shown in Tables 2 and 3, the coated carbide cutting tool of the present invention has a single-phase structure lower layer made of (Ti, Al, Cr) N, each having a hard coating layer having a different composition, It consists of an upper layer having an alternating laminated structure of thin layers A and B each having a thickness of 5 to 20 nm, the lower layer has excellent high-temperature hardness, and the upper layer has excellent heat-resistant plastic deformation. However, since the hard coating layer combines these excellent properties, even when gear cutting of alloy steel gears is performed under high-speed gear cutting conditions with high heat generation, chipping and uneven wear are prevented. The comparative coated carbide gear cutting tool in which the hard coating layer is composed of a (Ti, Al, Cr) N layer having a single phase structure, while exhibiting excellent wear resistance without occurrence, is the high-speed gear cutting processing described above. In particular, the wear progressed rapidly due to the lack of heat-resistant plastic deformation, It is clear that lead to specific short time service life.
As described above, the surface-coated cemented carbide gear cutting tool of the present invention (the coated carbide gear cutting tool of the present invention) is not only gear cutting under normal conditions, but also various alloy steel gears, etc. Even when the gear cutting is performed under high-speed gear cutting conditions with high heat generation, the hard coating layer exhibits excellent wear resistance and exhibits excellent performance over a long period of time. It is possible to satisfactorily cope with the high performance of the cutting device, the labor saving and energy saving of gear cutting, and the cost reduction.

The arc ion plating apparatus used for forming the hard coating layer which comprises the coated carbide gear cutting tool of this invention is shown, (a) is a schematic plan view, (b) is a schematic front view. It is a schematic explanatory drawing of a normal arc ion plating apparatus. It is a schematic perspective view of a cemented carbide cutting tool (solid hob).

Claims (1)

On the surface of the tungsten carbide base cemented carbide cutting tool base,

(A) Both are composed of an upper layer and a lower layer made of a composite nitride of Ti, Al, and Cr, the upper layer has an average layer thickness of 0.5 to 1.5 μm, and the lower layer has an average layer thickness of 2 to 6 μm. Have
(B) Each of the upper layers has an alternately laminated structure of thin layers A and B each having an average layer thickness of 5 to 20 nm (nanometer),
The thin layer A is
Ti satisfying the composition formula: [Ti _{1− (A + B)} Al _A Cr _B ] N (wherein A represents 0.01 to 0.10 and B represents 0.40 to 0.60) A composite nitride layer of Al and Cr;
The thin layer B is
_{Formula: [Ti 1- (C + D} ) Al C Cr D] N ( provided that an atomic ratio, C is 0.20 to 0.35, D denotes the 0.15 to 0.30) and Ti which satisfies A composite nitride layer of Al and Cr,
(C) the lower layer has a single phase structure;
Ti satisfying the composition formula: [Ti _{1− (E + F)} Al _E Cr _F ] N (wherein E is 0.45 to 0.65 and F is 0.01 to 0.15 in atomic ratio) A composite nitride layer of Al and Cr;
A surface-coated cemented carbide cutting tool that exhibits excellent wear resistance in high-speed gear cutting of alloy steel, characterized in that the hard coating layer is formed by vapor deposition.

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