SURFACE-COATED CUTTING TOOL

Abstract

In a surface-coated cutting tool in which a hard coating layer having a total layer thickness of 0.5 to 10 μm is deposited on a surface of a tool body made of WC-based cemented carbide or TiCN-based cermet, the hard coating layer has an alternately laminated structure of A layers and B layers, in a case where the A layer is: (Al.sub.aTi.sub.1-a)N (here, a is in atomic ratio), the A layer satisfies 0.50≦a<0.75, in a case where the B layer is: (Al.sub.bTi.sub.1-b)N (here, b is in atomic ratio), the B layer satisfies 0.75≦b≦0.95, and when a layer thickness per layer of the A layers is represented by x (nm) and a layer thickness per layer of the B layers is represented by y (nm), 5y≧x≧3y and 250 (nm)≧x+y≧100 (nm) are satisfied.

Claims

1. A surface-coated cutting tool in which a hard coating layer having a total layer thickness of 0.5 to 10 μm is deposited on a surface of a tool body made of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet, wherein (a) the hard coating layer has an alternately laminated structure of A layers and B layers, (b) in a case where the A layer is expressed by a composition formula: (Al.sub.aTi.sub.1-a)N (here, a is in atomic ratio), the A layer satisfies 0.50≦a<0.75, (c) in a case where the B layer is expressed by a composition formula: (Al.sub.bTi.sub.1-b)N (here, b is in atomic ratio), the B layer satisfies 0.75≦b≦0.95, and (d) when a layer thickness per layer of the A layers is represented by x (nm) and a layer thickness per layer of the B layers is represented by y (nm), 5y≧x≧3y and 250 (nm)≧x+y≧100 (nm) are satisfied.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0042] FIG. 1 illustrates an arc ion plating apparatus used to form hard coating layers to be formed in a coated tool of the present invention and a comparative coated tool, in which FIG. 1(a) is a schematic plan view, and FIG. 1(b) is a schematic front view.

[0043] FIG. 2 is a schematic explanatory view of an existing arc ion plating apparatus used to describe the related art.

DESCRIPTION OF EMBODIMENTS

[0044] Next, examples of a coated tool of the present invention will be described in detail.

[0045] Although a coated tool having a tool body made of tungsten carbide (WC)-based cemented carbide is described herein, this can also be applied to a case where the tool body is made of titanium carbonitride (TiCN)-based cermet.

Example 1

[0046] As raw material powders, a WC powder, a VC powder, a Cr.sub.3C.sub.2 powder, and a Co powder each having an average grain size of 1 μm to 3 μm were prepared, and the raw material powders were mixed in mixing compositions shown in Table 1, were wet-mixed by a ball mill for 72 hours, and were dried. Thereafter, the resultant was press-formed into a compact at a pressure of 100 MPa, and the compact was sintered in a vacuum at 6 Pa under a condition in which the compact was maintained at a temperature of 1400° C. for one hour. After sintering, tool bodies A-1 to A-3 made of WC-based cemented carbide with an insert shape according to ISO standard CNMG 120408 were produced.

[0047] In addition, as raw material powders, a TiCN (TiC/TiN=50/50 in terms of weight ratio) powder, an Mo.sub.2C powder, a ZrC powder, an NbC powder, a TaC powder, a WC powder, a Co powder, and an Ni powder, each having an average grain size of 0.5 to 2 μm, were prepared, and the raw material powders were mixed in mixing compositions shown in Table 2, were wet-mixed by a ball mill for 24 hours, and were dried. Thereafter, the resultant was press-formed into a compact at a pressure of 100 MPa, and the compact was sintered in a nitrogen atmosphere at 2 kPa under a condition in which the compact was held at a temperature of 1500° C. for one hour. After sintering, tool bodies B-1 to B-3 made of TiCN-based cermet with an insert shape according to ISO standard CNMG 120408 were produced by honing with R: 0.03 mm on a cutting edge portion.

[0048] (a) Subsequently, each of the tool bodies A-1 to A-3 and B-1 to B-3 was subjected to ultrasonic cleaning in acetone and was dried. In this state, the tool bodies A-1 to A-3 and B-1 to B-3 were mounted along the outer circumferential portions on a rotating table in an arc ion plating apparatus illustrated in FIG. 1 at positions distant from the center axis by predetermined distances in a radial direction thereof. In addition, cathode electrodes (evaporation sources) made of an Al—Ti alloy for forming the A layers and an Al—Ti alloy for forming the B layers were disposed at positions opposing each other with the rotating table interposed therebetween.

[0049] (b) First, while the inside of the apparatus was evacuated and held in a vacuum at 0.1 Pa or lower, the inside of the apparatus was heated to 600° C. by a heater. Thereafter, a DC bias voltage of −1000 V was applied to the tool bodies that were being rotated while revolving on the rotating table. In addition, arc discharge was generated by allowing a current of 100 A to flow between the Al—Ti alloys (cathode electrodes) and anode electrodes such that the surfaces of the tool bodies were subjected to bombardment cleaning.

[0050] (c) Next, the atmosphere in the apparatus was held in a nitrogen atmosphere at 0.5 to 9.0 Pa, a DC bias voltage of −20 to −150 V was applied to the tool bodies that were being rotated while revolving on the rotating table, arc discharge was generated by allowing a current of 50 to 250 A to flow between the Al—Ti alloy electrode for forming the A layer as the cathode electrode (evaporation source) and the anode electrode, to form an A layer having a predetermined layer thickness. Next, arc discharge was generated by allowing a current of 50 to 250 A to flow between the Al—Ti alloy electrode for forming the B layer and the anode electrode to form a B layer having a predetermined layer thickness. These operations were alternately performed repetitively to deposit the hard coating layer having the alternately laminated structure of the A layers and the B layers having target compositions and target layer thicknesses shown in Table 3.

[0051] Accordingly, surface-coated inserts (hereinafter, referred to as present invention coated inserts) 1 to 10 as the coated tools of the present invention were produced.

[0052] In addition, for the purpose of comparison,

[0053] (a) Each of the tool bodies A-1 to A-3 and B-1 to B-3 was subjected to ultrasonic cleaning in acetone and was dried. In this state, the tool bodies A-1 to A-3 and B-1 to B-3 were mounted along the outer circumferential portions on the rotating table in the arc ion plating apparatus illustrated in FIG. 1 at positions distant from the center axis by predetermined distances in the radial direction thereof. In addition, Al—Ti alloys (hereinafter, each referred to as an Al—Ti alloy for forming a C layer and an Al—Ti alloy for forming a D layer) having different compositions were disposed as cathode electrodes at positions opposing each other with the rotating table interposed therebetween.

[0054] (b) First, while the inside of the apparatus was evacuated and held in a vacuum at 0.1 Pa or lower, the inside of the apparatus was heated to 600° C. by a heater. Thereafter, a DC bias voltage of −1000 V was applied to the tool bodies that were being rotated while revolving on the rotating table. In addition, arc discharge was generated by allowing a current of 100 A to flow between the Al—Ti alloys (cathode electrodes) and anode electrodes such that the surfaces of the tool bodies were subjected to bombardment cleaning.

[0055] (c) Next, the atmosphere in the apparatus was held in a nitrogen atmosphere at 0.5 to 9.0 Pa, a DC bias voltage of −20 to −150 V was applied to the tool bodies that were being rotated while revolving on the rotating table, arc discharge was generated by allowing a current of 50 to 250 A to flow between the Al—Ti alloy electrode for forming a C layer as the cathode electrode (evaporation source) and the anode electrode to deposit a C layer having a predetermined composition. Next, arc discharge was generated by allowing a current of 50 to 250 A to flow between the Al—Ti alloy electrode for forming a D layer and the anode electrode to deposit a D layer having a predetermined composition, whereby hard coating layers having alternately laminated layers with target compositions and target layer thicknesses shown in Table 4 are deposited.

[0056] Accordingly, surface-coated inserts (hereinafter, referred to as comparative coated inserts) 1 to 5 as comparative coated tools were produced.

[0057] Next, regarding the present invention coated inserts 1 to 10 and the comparative coated inserts 1 to 5, the composition of each of the layers exhibiting the alternately laminated structures of the hard coating layers was measured by performing energy-dispersive X-ray spectroscopy on the longitudinal section of the hard coating layers using a transmission electron microscope, and all of the results showed substantially the same compositions as the target compositions.

[0058] In addition, the average layer thickness of each of the layers exhibiting the alternately laminated structures of the hard coating layers was measured in a section using the transmission electron microscope, and all of the results showed substantially the same average values (average value of 5 points) as the target layer thicknesses.

[0059] The measurement values are shown in Tables 3 and 4.

[0060] Next, a cutting test was conducted on the present invention coated inserts 1 to 10 and the comparative coated inserts 1 to 5 under the following cutting conditions, and the flank wear width of a cutting edge was measured in each high-speed cutting work test.

[0061] Cutting Condition A:

[0062] Work material: a round bar according to JIS SCM440 (HB 330)

[0063] Cutting speed: 220 m/min

[0064] Depth of cut: 0.2 mm

[0065] Feed: 0.28 mm/rev

[0066] Cutting time: 5 minutes

[0067] A high-speed cutting work test of alloy steel (typical cutting speed and feed were respectively 165 m/min. and 0.25 mm/rev.) under the above conditions.

[0068] Cutting condition B:

[0069] Work material: a round bar according to JIS S45C (HB 250)

[0070] Cutting speed: 200 m/min

[0071] Depth of cut: 0.2 mm

[0072] Feed: 0.33 mm/rev

[0073] Cutting time: 5 minutes

[0074] A high-speed cutting work test of carbon steel (typical cutting speed and feed were respectively 150 m/min. and 0.25 mm/rev.) under the above conditions.

[0075] Cutting condition C:

[0076] Work material: a round bar according to JIS SKD61 (HRC 60)

[0077] Cutting speed: 110 m/min

[0078] Depth of cut: 0.2 mm

[0079] Feed: 0.28 mm/rev

[0080] Cutting time: 3 minutes

[0081] A high-speed cutting work test of high hardness steel (typical cutting speed and feed were respectively 70 m/min. and 0.1 mm/rev.) under the above conditions.

[0082] The measurement results are shown in Table 5.

[0083] [Table 1]

TABLE-US-00001 TABLE 2 Mixing composition (mass %) Type Co Ni ZrC TaC NbC Mo.sub.2C WC TiCN Tool B-1 12 5 — 10 — 10 16 Remainder body B-2 9 5 — 11 2 — — Remainder B-3 10 4 1 8 — 10 10 Remainder

TABLE-US-00002 TABLE 3 A layer B layer Value of Value of average average Relationship between x Compo- layer Compo- layer and y of A layer and B sition of thickness sition thickness layer Total Tool A layer x per of B layer y per Value Value Number of layer body (value of layer (value of layer of of laminated thickness Type symbol a) (nm) b) (nm) x/y (x + y) units (μm) Present 1 A-1 0.50 80 0.90 20 4.0 100 38 3.80 invention 2 A-2 0.74 90 0.95 20 4.5 110 90 9.90 coated 3 A-3 0.65 150 0.75 40 3.8 190 50 9.50 inserts 4 A-1 0.70 200 0.75 50 4.0 250 40 10.0 5 A-2 0.50 90 0.80 30 3.0 120 60 7.20 6 A-3 0.73 185 0.85 55 3.4 240 4 0.96 7 B-1 0.74 85 0.90 25 3.4 110 60 6.60 8 B-2 0.70 76 0.95 24 3.2 100 5 0.50 9 B-3 0.69 185 0.90 55 3.4 240 15 3.60 10 B-1 0.68 200 0.85 40 5.0 240 3 0.72

TABLE-US-00003 TABLE 4 Hard coating layer C layer D layer Value of Value of average average Relationship between Compo- layer Compo- layer x and y of C layer Total sition of thickness sition of thickness and D layer layer Tool C layer x per D layer y per Value Value Number of thick- body (value of layer (value of layer of of laminated ness Type symbol a) (nm) b) (nm) x/y (x + y) units (μm) Comparative 1 A-1 0.60 40 0.90 20 2.0 60 10 0.6 coated 2 A-2 0.30 90 0.50 20 4.5 110 50 5.5 Inserts 3 A-3 0.78 120 0.95 30 4.0 150 40 6 4 B-1 0.65 90 0.70 20 4.5 110 10 1.1 5 B-2 0.60 150 0.85 200 0.8 350 30 10.5

TABLE-US-00004 TABLE 5 Flank wear width (mm) Flank wear width (mm) Cutting Cutting Cutting Cutting Cutting Cutting condition condition condition condition condition condition Type (A) (B) (C) Type (A) (B) (C) Present 1 0.21 0.23 0.23 Comparative 1 4.0* 4.2* 3.5* invention 2 0.21 0.22 0.25 coated 2 4.3* 4.8* 3.6* coated 3 0.20 0.24 0.28 inserts 3 4.6* 4.5* 3.7* inserts 4 0.18 0.26 0.27 4 4.5* 4.3* 3.8* 5 0.22 0.23 0.26 5 4.1* 4.3* 3.7* 6 0.19 0.24 0.23 7 0.18 0.25 0.22 8 0.22 0.25 0.27 9 0.20 0.23 0.24 10 0.20 0.26 0.28 Mark * in boxes of comparative coated inserts indicates a cutting time (min) until the end of a service life caused by abnormal damage to a cutting edge portion.

Example 2

[0084] As in Example 1, raw material powders including a WC powder, a VC powder, a Cr.sub.3C.sub.2 powder, and a Co powder each having an average grain size of 1 to 3 μm were mixed in mixing compositions shown in Table 1, were wet-mixed by a ball mill for 72 hours, and were dried. Thereafter, the resultant was press-formed into a compact at a pressure of 100 MPa, and the compact was sintered in a vacuum at 6 Pa under the condition that the compact was held at a temperature of 1400° C. for one hour, thereby forming a round bar sintered body for forming a tool body having a diameter of 13 mm. Furthermore, from the round bar sintered body, by performing grinding, each of the tool bodies (end mills) A-1 to A-3 made of WC-based cemented carbide having a four-edge square shape with a helix angle of 30 degrees in dimensions of 10 mm×22 mm as the diameter×the length of the cutting edge portion were produced.

[0085] Next, the surfaces of the tool bodies (end mills) A-1 to A-3 were subjected to ultrasonic cleaning in acetone and were dried. In this state, the tool bodies A-1 to A-3 were loaded into the same arc ion plating apparatus illustrated in FIG. 1 and hard coating layers having an alternately laminated structure of A layers and B layers with target compositions and target layer thicknesses shown in Table 6 were deposited under the same conditions as in Example 1. Accordingly, each of present invention surface-coated cemented carbide end mills (hereinafter, referred to as present invention coated end mills) 1 to 6 as present invention coated tools were produced.

[0086] In addition, for the purpose of comparison, the surfaces of the tool bodies (end mills) A-1 to A-3 were subjected to ultrasonic cleaning in acetone and were dried. In this state, the tool bodies A-1 to A-3 were loaded into the same arc ion plating apparatus illustrated in FIG. 1 and hard coating layers having alternately laminated layers with target compositions and target layer thicknesses shown in Table 7 were deposited in the same process as in Example 1. Accordingly, each of surface-coated cemented carbide end mills (hereinafter, referred to as comparative coated end mills) 1 to 5 as comparative coated tools were produced.

[0087] Next, regarding the present invention coated end mills 1 to 6 and the comparative coated end mills 1 to 5, the composition of each of the layers exhibiting the alternately laminated structures of the hard coating layers was measured by performing energy-dispersive X-ray spectroscopy on the longitudinal section of the hard coating layers using the transmission electron microscope, and all of the results showed substantially the same compositions as the target compositions.

[0088] In addition, the average layer thickness of each of the layers exhibiting the alternately laminated structures of the hard coating layers was measured in a section using the transmission electron microscope, and all of the results showed substantially the same average values (average value of 5 points) as the target layer thicknesses.

[0089] The measurement values are shown in Tables 6 and 7.

[0090] Next, regarding the present invention coated end mills 1 to 6 and comparative coated end mills 1 to 5,

Work material−a plate material of JIS SCM440 (HB 330) having planar dimensions of 100 mm×250 mm and a thickness of 50 mm

[0091] Cutting speed: 240 m/min.

[0092] Groove depth (depth of cut): 15 mm

[0093] Table feed: 820 mm/min.

[0094] Under the above conditions (cutting condition D), a wet high-speed groove cutting work test (typical cutting speed and table feed were respectively 190 m/min. and 650 mm/min.) of chromium-molybdenum steel was conducted, and the cutting groove length until the flank wear width of the outer circumferential edge of the cutting edge portion had reached 0.1 mm, which is regarded as a measure of the service life, was measured.

[0095] The measurement results are shown in Tables 6 and 7, respectively.

TABLE-US-00005 TABLE 6 A layer B layer Value of Value of Cutting average average Relationship between test Compo- layer Compo- layer x and y of A layer results sition thickness sition thickness and B layer Total Cutting Tool of A layer x per of B layer y per Value Value Number of layer groove body (value of layer (value of layer of of laminated thickness length Type symbol a) (nm) b) (nm) x/y (x + y) units (μm) (m) Present 1 A-1 0.65 80 0.95 20 4.0 100 5 0.5 120 Invention 2 A-2 0.50 100 0.95 20 5.0 120 50 6.0 130 coated 3 A-3 0.74 140 0.75 40 3.5 180 40 7.2 125 end mills 4 A-1 0.55 200 0.90 50 4.0 250 40 10.0 120 5 A-2 0.50 99 0.80 33 3.0 132 25 3.3 135 6 A-3 0.68 90 0.85 30 3.0 120 50 6.0 135

TABLE-US-00006 TABLE 7 Hard coating layer C layer D layer Value of Value of Cutting average average Relationship between test Compo- layer Compo- layer x and y of C layer results sition thickness sition thickness and D layer Total Cutting Tool of C layer x per of D layer y per Value Value Number of layer groove body (value of layer (value of layer of of laminated thickness length Type symbol a) (nm) b) (nm) x/y (x + y) units (μm) (m) Comparative 1 A-1 0.55 20 0.90 40 0.5 60 10 0.6 41 coated end 2 A-2 0.80 80 0.75 20 4.0 100 50 5.0 46 mills 3 A-3 0.78 90 0.70 30 3.0 120 80 9.6 45 4 A-1 0.50 90 0.98 20 4.5 110 50 5.5 48 5 A-2 0.50 150 0.85 40 3.8 190 60 11.4 46

[0096] From the results shown in Tables 5 to 7, in the present invention coated tools, on each of the surfaces of the tool bodies, the hard coating layer having an alternately laminated structure of A layers and B layers with a predetermined composition and a layer thickness was formed, and thus the hard coating layer has excellent heat resistance and high hardness. Accordingly, during high-speed cutting work of carbon steel, alloy steel, high hardness steel, and the like, excellent wear resistance is exhibited for a long-term use without the occurrence of abnormal damage such as chipping, fracturing, and peeling.

[0097] Contrary to this, in the comparative coated tools in which any one of the layers constituting the hard coating layers deviated from the composition, layer thickness, and the like specified in the present invention, it was apparent that the wear resistance was insufficient, and the service life was reached within a relatively short period of time.

INDUSTRIAL APPLICABILITY

[0098] As described above, the coated tools of the present invention exhibit excellent wear resistance and excellent cutting performance over a long period of time not only during a high-speed cutting work of carbon steel, alloy steel, high hardness steel, and the like, but also during the cutting work of a general work material. Therefore, the coated tools of the present invention can satisfactorily cope with the automation of cutting work apparatuses, power saving and energy saving during the cutting work, and a further reduction in costs.