JP4706912B2 - Surface-coated cemented carbide cutting tool with excellent wear resistance due to high-speed gear cutting of alloy steel - Google Patents

Description

  In the present invention, the hard coating layer has excellent thermal conductivity, and also has high-temperature oxidation resistance in addition to high-temperature hardness and high-temperature strength. Therefore, particularly for high-speed gear cutting with high heat generation such as alloy steel. The present invention also relates to a surface-coated cemented carbide gear cutting tool (hereinafter referred to as a coated carbide gear cutting tool) that exhibits excellent wear resistance even when used.

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 base (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,

Composition formula: Cr—Al-based composite nitride represented by [Cr _1-X Al _X ] N (wherein X represents 0.50 to 0.70 in atomic ratio) [hereinafter referred to as (Cr, Al) And the like are known. The (Cr, Al) N layer constituting the hard coating layer has high-temperature hardness due to Al as a constituent component, high-temperature strength due to the Cr, and excellent high-temperature oxidation resistance due to the coexistence of Cr and Al. Therefore, it is also known that a coated gear cutting tool formed with such a hard coating layer exhibits excellent gear cutting performance.

Furthermore, the above-described coated cutting tool is loaded with the above-mentioned substrate in an arc ion plating apparatus which is one type of physical vapor deposition apparatus schematically shown in FIG. 2, for example, and the atmosphere is set to a vacuum atmosphere of 2 Pa, for example. In a state in which the inside of the apparatus is heated to a temperature of 500 ° C. with a heater, for example, a voltage: 35 V, a current: between the anode electrode and a cathode electrode (evaporation source) on which a Cr—Al alloy having a predetermined composition is set. An arc discharge was generated under the condition of 90 A, and simultaneously, nitrogen gas was introduced into the apparatus as a reaction gas to form a reaction atmosphere of 2 Pa, for example. On the other hand, a bias voltage of −200 V, for example, was applied to the substrate. It is also known that it is produced by vapor-depositing a hard coating layer composed of the (Cr, Al) N layer on the surface of the substrate.
Patent No. 3027502

In recent years, the performance of gear cutting machines has been remarkably improved. On the other hand, there is a strong demand for labor saving and energy saving and further cost reduction for gear cutting, and with this, gear cutting has a tendency to increase in speed. In the above conventional coated 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, a hard coating layer is used. As the thermal conductivity (heat removal effect) of is not sufficient, the cutting edge part is subject to thermoplastic deformation that causes uneven wear, the wear progress is promoted, and the service life is reached in a relatively short time. It is.

Therefore, the present inventors, from the above viewpoint, in order to develop a coated high-speed gear cutting tool that exhibits excellent thermal conductivity and wear resistance, especially in high-speed gear cutting of alloy steel, As a result of conducting research focusing on the hard coating layer of the conventional coated high-speed gear cutting tool,

(A) When B is contained as a component of the (Cr, Al) N layer constituting the hard coating layer and a composite nitride layer of Cr, Al and B is formed, the hard coating layer can be obtained by increasing the B content ratio. However, the high thermal conductivity required for high-speed gear cutting of alloy steel cannot be ensured only by containing about 1 to 10 atomic% of B. However, in order to satisfy these requirements satisfactorily, it is necessary to contain 20 to 35 atomic% of B, far exceeding the above 1 to 10 atomic%. However, in order to practically use a (Cr, Al, B) N layer containing 20 to 35 atomic% of B component as a hard coating layer, at least a predetermined amount of Cr is contained as a component of the hard coating layer. In this case, it is inevitable that the content ratio of the Al component is extremely low, and as a result, the high temperature hardness and heat resistance are extremely low.

(B) Composition formula: (Cr _{1− (E + F)} Al _E B _F ) N (provided that the atomic ratio indicates that E is 0.01 to 0.10 and F is 0.20 to 0.35) A (Cr, Al, B) N layer having a B content of 20 to 35 atomic%;
Composition formula: (Cr _{1− (M + N)} Al _M B _N ) N (wherein, in terms of atomic ratio, M is 0.25 to 0.40, D is 0.10 to 0.20), relative (Cr, Al, B) N layer with an increased content ratio of Al component,
Are alternately laminated in a state where each layer thickness is 5 to 20 nm (nanometer), the (Cr, Al, B) N layer is formed by the above-mentioned high B by the thin laminated structure. The excellent thermal conductivity of the contained (Cr, Al, B) N layer (hereinafter referred to as the thin layer A), the B content ratio is relatively low as compared with the thin layer A, and the relative Al content A predetermined relatively high high temperature hardness and heat resistance of the (Cr, Al, B) N layer (hereinafter referred to as the thin layer B) having a high content ratio.

(C) The (Cr, Al, B) N layer having the alternately laminated structure of the thin layer A and the thin layer B in (b) has high thermal conductivity required for high-speed gear cutting of alloy steel. However, since it does not have sufficiently satisfactory high-temperature hardness and heat resistance, it is provided as the upper layer of the hard coating layer, while the lower layer is relatively insufficient in thermal conductivity, (Cr, Al, B) N layer, which is a hard coating layer having a high Al component content, excellent high-temperature hardness and heat resistance,
Composition formula: (Cr _{1− (X + Y)} Al _X B _Y ) N (wherein X is 0.50 to 0.70 and Y is 0.01 to 0.10 in atomic ratio) (Cr, Al, B) N layer of single phase structure,
With this structure, the hard coating layer has high-temperature hardness, heat resistance, and high-temperature strength in addition to excellent thermal conductivity. Therefore, the hard coating layer is formed by vapor deposition. The coated carbide gear cutting tool has high thermal conductivity required for high speed gear cutting of alloy steel with high heat generation, and exhibits excellent wear resistance 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 (Cr, Al, B) 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: (Cr _{1− (E + F)} Al _E B _F ) N (wherein E is 0.01 to 0.10 and F is 0.20 to 0.35 in atomic ratio) (Cr , Al, B) N layer,

The thin layer B is

Composition formula: (Cr _{1− (M + N)} Al _M B _N ) N (wherein M is 0.25 to 0.40 and D is 0.10 to 0.20 in atomic ratio) (Cr , Al, B) N layer,

(C) the lower layer has a single phase structure;
Composition formula: (Cr _{1− (X + Y)} Al _X B _Y ) N (wherein X is 0.50 to 0.70 and Y is 0.01 to 0.10 in atomic ratio) (Cr , Al, B) 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, the reason for limiting the configuration of the hard coating layer constituting the coated carbide gear cutting tool of the present invention as described above will be described.

(A) Composition formula and layer thickness of lower layer As described above, the Al component in the (Cr, Al, B) N layer constituting the hard coating layer improves the high-temperature hardness and heat resistance, while the Cr component Has the effect of improving the high-temperature strength and further the thermal conductivity of the B component. In the lower layer, the Al component content is relatively increased to provide high high-temperature hardness and heat resistance. If the X value indicating the content ratio is less than 0.50 in the ratio of the total amount of Cr and B (atomic ratio, the same shall apply hereinafter), the ratio of Cr is relatively high, and high speed gear cutting of alloy steel. The required high-temperature hardness and heat resistance cannot be ensured, and the progress of wear is rapidly promoted. On the other hand, if the X value indicating the proportion of Al exceeds 0.70, the relative In addition, the ratio of Cr becomes too small, and the high-temperature strength rapidly decreases. As a result, chipping (slight chipping) and the like are likely to occur, so the X value was set to 0.50 to 0.70.
Further, the Y value indicating the ratio of B is the ratio of the total amount of Cr and Al, and if it is less than 0.01, the predetermined thermal conductivity cannot be ensured, while the Y value is 0.10. If it exceeds, the high temperature hardness and the heat resistance will decrease rapidly, so the Y value was determined to be 0.01 to 0.10.
Furthermore, if the layer thickness is less than 2 μm, the excellent high-temperature hardness and heat resistance cannot be imparted to the hard coating layer over a long period of time, resulting in a shortened tool life, while the layer thickness exceeds 6 μm. Then, since the chipping is likely to occur, the layer thickness is set to 2 to 6 μm.

(B) Composition formula of the thin layer A of the upper layer The B component in (Cr, Al, B) N of the thin layer A of the surface layer has a relatively high content ratio as described above, and the thermal conductivity is increased. F value that shows the content ratio, which has the effect of improving the heat removal effect of high-speed gear cutting of alloy steel with high heat generation and preventing the occurrence of thermoplastic deformation causing uneven wear. Is less than 0.20, the desired excellent thermal conductivity cannot be ensured. On the other hand, if the F value exceeds 0.35, the high temperature strength that the layer itself should have cannot be ensured, and chipping is not possible. Since it becomes easy to generate | occur | produce, F value was set to 0.20-0.35.

Further, the E value indicating the proportion of Al is the proportion of the total amount of Cr and B, and if it is less than 0.01, the minimum high-temperature hardness and heat resistance cannot be ensured, which causes accelerated wear. On the other hand, if the E value exceeds 0.10, a tendency to decrease in the high temperature strength appears, which causes the occurrence of chipping. Therefore, the E value was set to 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 B component is relatively lower than that of the thin layer A, and the content ratio of the Al component is relatively By keeping the thin layer A high, the thin layer A has insufficient high-temperature hardness and heat resistance, reinforces the high-temperature hardness and heat resistance shortage of the adjacent thin layer A, and thus has the excellent thin layer A. The upper layer having the heat conductivity and the relatively high high-temperature hardness and heat resistance of the thin layer B is formed, and the M value indicating the Al content in the composition formula is 0.25. If the M value is less than 0.40, the predetermined high-temperature hardness and heat resistance cannot be ensured, which causes accelerated wear. On the other hand, if the M value exceeds 0.40, the high-temperature strength suddenly decreases. Since chipping is likely to occur in the upper layer, the M value is set to 0.25 to 0.25. It was set to 0.40.

Further, the N value indicating the ratio of B is the ratio of the total amount of Cr and Al. If the N value is less than 0.10, a decrease in the thermal conductivity of the entire upper layer is inevitable, while the N value is 0.20. When exceeding, since the high temperature strength of the whole upper layer will fall rapidly, N value was defined as 0.10-0.20.

(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 thermal conductivity, predetermined high-temperature hardness and heat resistance cannot be ensured, and if the thickness of each layer exceeds 20 nm, the disadvantages of each thin layer, that is, if thin layer A is high-temperature hardness If the heat resistance is insufficient and the thin layer B, a decrease in thermal conductivity appears locally in the layer, and this is likely to cause chipping or promote the progress of wear. The thickness was set to 5 to 20 nm.

(E) Layer thickness of the upper layer If the layer thickness is less than 0.5 μm, the excellent thermal conductivity and predetermined high-temperature hardness and heat resistance 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 1.5 μm, chipping tends 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 the (Cr, Al, B) N layer, and the upper layer of the hard coating layer is formed by alternately laminating the thin layer A and the thin layer B.・ Providing excellent thermal conductivity while maintaining the specified high-temperature hardness and heat resistance, and the lower layer of the single-phase structure has excellent high-temperature hardness and heat resistance. Even in high-speed gear cutting of alloy steel that is easy to promote, the hard coating layer exhibits excellent heat removal effect. As a result, there is no occurrence of thermoplastic deformation that causes uneven wear on the cutting edge, and the cutting edge is normally worn. It takes a form and exhibits excellent wear resistance 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 × Length: Solid hob type carbide gear cutting bases A to J shown in FIG. 3 each having the overall dimensions of 120 mm and the shape of three right-handed twists × 19 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 Cr-Al-B alloy for forming A, Cr-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 B alloy is placed opposite to the rotary table, and Cr-Al- for forming a lower layer as a cathode electrode (evaporation source) along the rotary table at a position shifted by 90 degrees from both the Cr-Al-B alloys. Wearing B alloy And,
(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 Cr—Al—B alloy for forming the lower layer and the anode electrode to generate an arc discharge. Bombarded with Cr-Al-B 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 flowing a current of 100 A between the lower layer forming Cr—Al—B alloy and the anode electrode, and the target composition and target shown in Table 2 are formed on the surface of the cemented carbide cutting base. (Cr, Al, B) 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 Cr-Al-B alloy for forming the thin layer A to generate arc discharge, and the cemented carbide cutting A thin layer A having a predetermined layer thickness is formed on the surface of the substrate. After the thin layer A is formed, the arc discharge is stopped, and instead, between the cathode electrode and the anode electrode of the Cr-Al-B 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). May be used again to form the thin layer A. Formation of thin layer A by arc discharge between the cathode electrode and anode electrode of r-Al-B alloy, and thin layer B by arc discharge between the cathode electrode and anode electrode of Cr-Al-B alloy for forming thin layer B Are alternately and repeatedly formed on the surface of the cemented carbide substrate by alternating lamination of thin layers A and B having a target composition and a single target layer thickness shown in Table 2 along the layer thickness direction. Similarly, the coated carbide carbide cutting tools 1 to 10 of the present invention were manufactured by vapor-depositing the upper layer with the entire target layer thickness shown in Table 2.

  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 Cr—Al—B 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 between the Cr—Al—B alloy of the cathode electrode and the anode electrode was applied. When an electric current is passed to generate an arc discharge, the surface of the carbide cutting base is bombarded with the Cr—Al—B 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, and arc discharge is generated between the cathode electrode and the anode electrode of the Cr—Al—B alloy, thereby the carbide cutting base. A comparative coated carbide gear cutting tool is formed by vapor-depositing a hard coating layer composed of a (Cr, Al, B) 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: 1.75, pressure angle: 17.5 degrees, number of teeth: 47, helix angle: 30 degrees right twist, tooth width: 25mm

Cutting speed (rotational speed): 500 m / min,
Feed: 1.5mm / 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.

The thin layer A and the thin layer B constituting the hard coating layer made of (Cr, Al, B) N of the coated carbide cutting tool 1-10 of the present invention obtained as a result of this, and the composition of the lower layer In addition, the composition of the hard coating layer made of (Cr, Al, B) N of the comparative coated carbide gear cutting tools 1 to 10 was measured by an energy dispersive X-ray analysis method 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 (Cr, Al, B) N, each of which has a different hard coating layer composition, It consists of an upper layer having an alternating layer 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 thermal conductivity. In addition, since the hard coating layer combines these excellent characteristics, even when gear cutting of alloy steel gears is performed under high-speed gear cutting conditions with high heat generation, the hard coating layer is Excellent heat removal effect is achieved by the upper layer, and excellent wear resistance is exhibited without the occurrence of thermoplastic deformation that causes uneven wear at the cutting edge, whereas the hard coating layer has a single-phase structure. The comparative coated carbide gear cutting tool composed of (Cr, Al, B) N layer is Under gear cutting conditions, especially the thermal deformation of the cutting edge occurs due to insufficient thermal conductivity, and this causes the wear form to become an uneven wear form. It is clear that the service life is reached.
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 Cr, Al, and B (boron), the upper layer being an average layer of 0.5 to 1.5 μm, and the lower layer being an average layer of 2 to 6 μm Each has a thickness,
(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
Composition formula: [Cr _{1− (E + F)} Al _E B _F ] N (wherein, in terms of atomic ratio, E represents 0.01 to 0.10, F represents 0.20 to 0.35) and Cr A composite nitride layer of Al and B;
The thin layer B is
Composition _{formula: [Cr 1- (M + N} ) Al M B N] N ( provided that an atomic ratio, M is 0.25 to 0.40, N denotes the 0.10 to 0.20) and Cr satisfying a A composite nitride layer of Al and B,
(C) the lower layer has a single phase structure;
Composition formula: [Cr _{1− (X + Y)} Al _X B _Y ] N (wherein, in terms of atomic ratio, X represents 0.50 to 0.70, Y represents 0.01 to 0.10) and Cr A composite nitride layer of Al and B;
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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