Hard-coated cutting tools

Abstract

On the surface of the tool substrate, a (Me 1-x—y Al x M y )N z 1. A surface-coated cutting tool having a hard coating layer containing a hard coating having an average composition of (0.35≦x≦0.80, 0.00≦y≦0.20, 0.20≦(1−xy)≦0.65, 0.90≦z≦1.10 (wherein Me is Ti or Cr, x, y, and z are atomic ratios, and M is at least one of an element of Groups 4 to 6 of the IUPAC periodic table, Y, Si, La, and Ce)), wherein the ratio of N to the total amount of Ti, Al, M, and N in an interface region of the hard coating layer having an average thickness of 5 to 100 nm from the surface of the tool substrate toward the tool surface is 10 to 30 atomic % on the surface side of the tool substrate and increases from the surface of the tool substrate toward the tool surface.

Description

[Technical Field]

[0001] The present invention relates to a surface-coated cutting tool (hereinafter sometimes referred to as a coated tool). [Background technology]

[0002] Generally, coated tools include inserts that are detachably attached to the tip of a cutting tool for turning and planing workpieces such as various types of steel (carbon steel, alloy steel) and cast iron, drills and miniature drills that are used for drilling and cutting the same workpieces, and solid-type end mills that are used for facing, grooving, shouldering, and other workpiece machining.In addition, insert-type end mills that have detachable inserts and perform cutting operations in the same way as solid-type end mills are also known.

[0003] Conventionally, coated tools have been known which have a tool substrate made of, for example, a WC-based cemented carbide, a TiCN-based cermet, a cBN sintered body, or the like, on which a hard coating layer is formed, and various proposals have been made to improve cutting performance.

[0004] For example, Patent Document 1 describes a hard-coated tool having a lower layer, an intermediate layer, and an upper layer formed on a tool substrate, (a) the lower layer contains at least one metal element selected from the group consisting of elements of Groups IV, V, and VI, Al, and Si, and at least one nonmetal element selected from the group consisting of N, C, and B; (b) The upper layer is (Al x Cr y ) c O d (x=0.1 to 0.40, x+y=1, c=1.86 to 2.14, d=2.79 to 3.21), having an α-type crystal structure, and having an equivalent X-ray diffraction intensity ratio TC(110) of 1.3 or more, TC(110) being greater than TC(104), and TC(006) being 0; (c) The intermediate layer is made of an oxynitride containing Al and Cr as essential metal elements, and has a gradient composition in which the oxygen concentration increases from the lower layer side to the upper layer side and the nitrogen concentration decreases from the lower layer side to the upper layer side, and the average composition (Al s Cr t ) a (N v O w ) b satisfies s=0.1~0.6, s+t=1, v=0.1~0.8, v+w=1, a=0.35~0.6, a+b=1. A hard-coated tool characterized by is stated.

[0005] Furthermore, Patent Document 2 describes a tool substrate having a surface that is formed of a total of two layers, a first layer of TiAl nitride and a second layer of TiAl nitride, in that order, where Ti:Al:N=α:β:γ, (1) The TiAl nitride of the first layer satisfies 0<α / β≦3, 0.2≦(α+β) / γ≦2, (2) The second layer of TiAl nitride satisfies 0<α / β≦3, and T=(α+β) / γ, and T1T2T3T4···T is continuous or intermittent from the substrate side to the surface side. n (n is arbitrary), then 2 ≥ T1>T2>T3>T4> >T n ≧0.1, Hard-coated cutting tools is stated.

[0006] Furthermore, Patent Document 3 discloses a method for forming a thin film of Al on a wear-resistant substrate. a M b(M is at least one selected from the group consisting of Ti, Ta, V, Cr, Zr, Nb, Mo, Hf, W, Fe, Co, Ni, Cu, and Mn. 60 at% ≦ a ≦ 98.5 at%, 1.5 at% ≦ b ≦ 40 at%). Using an evaporation source material having such a composition, while controlling the supply amount of a reaction gas containing nitrogen, oxygen, or carbon so that its partial pressure changes continuously or stepwise, an amorphous hard film having a high hardness with the concentration of the reaction gas component in the amorphous film increasing toward the film surface is described, and it has been shown that this hard film can be used as an electric and electronic material, a high-strength material, a wear-resistant material, a high-temperature resistant material, etc.

[0007] In addition, Patent Document 4 describes a composite coated with an abrasion-resistant surface layer having two coating layers on a substrate. When the composition of the coating layer is MeNx, 0.5 < x < 0.9 for the inner coating layer and 0.9 < x ≦ 1.0 for the outer coating layer, and Me is a metal belonging to Groups III to IV of the periodic table, and it has been shown that this composite can be used as a cutting tool.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0009] The coated tools having hard coating layers (wear-resistant layers) described in Patent Documents 1 to 4 reach high cutting temperatures at the cutting edge during high-speed cutting of carbon steel, alloy steel, stainless steel, cast iron, etc., which causes early changes in the composition of the hard coating layer, making the hard coating layer brittle and shortening the lifespan, making it difficult to achieve satisfactory cutting performance. In this specification, high-speed cutting refers to high-speed cutting that is 15% or more faster than normal cutting speeds, particularly for stainless steel, which generates a lot of heat during cutting, and 30% or more faster than conventional cutting speeds for carbon steel, alloy steel, and cast iron.

[0010] Therefore, an object of the present invention is to provide a cutting tool that exhibits excellent cutting performance over long periods of use by providing a hard coating layer with excellent chipping resistance, even when used for high-speed cutting of carbon steel, alloy steel, stainless steel, cast iron, etc. [Means for solving the problem]

[0011] The surface-coated cutting tool according to one embodiment of the present invention is the following (1) and (2). (1) A tool substrate and a hard coating layer having an average thickness of at least 0.5 to 10.0 μm on the surface of the tool substrate, The tool substrate has an interface region on the surface side. 1. A surface-coated cutting tool comprising a composite nitride coating, The composite nitride coating has the composition formula: (Ti 1-x―y Al x M y )N z When expressed as above, the average composition satisfies 0.35≦x≦0.80, 0.00≦y≦0.20, 0.20≦(1−xy)≦0.65, and 0.90≦z≦1.10 (where x, y, and z are atomic ratios, and M is at least one of an atom of Groups 4 to 6 of the IUPAC periodic table, Y, Si, La, and Ce), The interface region is above the surface of the tool substrate In The average thickness towards the tool surface is in the range of 5 to 100 nm. the law of nature The content ratio of N to the total amount of Ti, Al, M and N is 10 to 30 atomic % on the surface side of the tool substrate, and side from the tool surface.

[0012] (2) A tool substrate and a hard coating layer having an average thickness of at least 0.5 to 10.0 μm on the surface of the tool substrate, The tool substrate has an interface region on its surface side. 1. A surface-coated cutting tool comprising a composite nitride coating, The composite nitride coating has the composition formula: (Cr 1-x―y Al x M y )N z When expressed as above, the average composition satisfies 0.35≦x≦0.80, 0.00≦y≦0.20, 0.20≦(1−xy)≦0.65, and 0.90≦z≦1.10 (where x, y, and z are atomic ratios, and M is at least one of an atom of Groups 4 to 6 of the IUPAC periodic table, Y, Si, La, and Ce), The interface region is The average thickness of the tool substrate from above the surface toward the tool surface is in the range of 5 to 100 nm. the law of nature The content ratio of N to the total amount of Cr, Al, M and N is 10 to 30 atomic % on the surface side of the tool substrate, and side from the tool surface. [Effects of the Invention]

[0013] A surface-coated cutting tool having a composite nitride coating containing Al, Ti, and M in its hard coating layer can be used for high-speed cutting of alloy steel, cast iron, etc., while a surface-coated cutting tool having a composite nitride coating containing Al, Cr, and M in its hard coating layer can be used for high-speed cutting of carbon steel, stainless steel, etc. Because the hard coating layer has excellent chipping resistance, the tool exhibits excellent cutting performance over long periods of use. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram of a vertical cross section of a hard coating layer in a surface-coated cutting tool according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present inventors have conducted extensive research into the physical properties of hard coating layers having a composite nitride coating containing Al, Ti, and M, and a composite nitride coating containing Al, Cr, and M (wherein M is at least one of the elements Y, Si, La, and Ce, which are groups 4 to 6 of the IUPAC periodic table; hereinafter, these may be referred to as a (TiAlM)N coating and a (CrAlM)N coating, respectively). As a result, the following findings were obtained.

[0016] (1) Hard coating layers containing low-N content (TiAlM)N and (CrAlM)N films have excellent wear resistance even during high-speed cutting. This is presumably due to the high thermal stability of these coatings. (2) Increasing the N content (content ratio) from the surface of the tool substrate toward the tool surface in the interface region between the tool substrate and the hard coating (a predetermined range of the hard coating layer near the surface of the tool substrate) improves cutting performance. This is presumably because increasing the N content ratio makes it difficult for the hard coating layer to decompose, suppressing cracks that occur near the interface and improving the adhesion of the hard coating layer. Although Patent Documents 1 to 4 describe films with varying N content, none of them even suggest the findings of (1) and (2) above.

[0017] A coated tool according to one embodiment of the present invention will be described in more detail below. In this specification and claims, when a numerical range is expressed using "A to B" (where A and B are both numerical values), the range includes the upper limit (B) and the lower limit (A). The upper limit (B) and the lower limit (A) have the same units. All numerical values ​​allow for measurement tolerances.

[0018] Hard Coating: As shown in FIG. 1, the hard coating layer 4 of the coated tool of this embodiment has a (TiAlM)N coating or a (CrAlM)N coating included in a hard coating 3 provided on a tool substrate 1, and has an interface region 2 of a predetermined range near the surface of the tool substrate 1.

[0019] The average thickness of the hard coating layer is preferably 0.5 to 10.0 μm. The reason for this range is that if the average thickness is less than 0.5 μm, excellent wear resistance cannot be exhibited over long periods of use, while if the average thickness is more than 10.0 μm, the crystal grains tend to become coarse, making it difficult to obtain improved chipping resistance.

[0020] (TiAlM)N and (CrAlM)N coatings: The (TiAlM)N coating contained in the hard coating layer of the coated tool of this embodiment has an average composition represented by the formula: (Ti 1-x-y Al x M y )N z The average composition of the (CrAlM)N coating is expressed as follows: 1-x-y Al x M y )N z When expressed as above, both have average compositions that satisfy the following conditions: 0.35≦x≦0.80, 0.00≦y≦0.20, 0.20≦(1−xy)≦0.65, 0.90≦z≦1.10 (where x, y, and z are atomic ratios, and M is at least one of Y, Si, La, and Ce, an atom of Groups 4 to 6 of the IUPAC periodic table).

[0021] The reason for determining the ranges of x, y, 1-xy, and z in this way is as follows. If the value of x is less than 0.35, not only will high hardness not be achieved, but the crystal grains will tend to become coarse, while if it exceeds 0.80, the crystal structure of some crystals will change from the NaCl-type face-centered cubic structure to a hexagonal structure, resulting in a decrease in hardness. A more preferable range is 0.45≦x≦0.70.

[0022] Furthermore, if the average content y of M, which is added as needed, exceeds 0.20, the toughness decreases, and chipping and fractures tend to occur. Furthermore, if the value of (1-xy) is less than 0.20, the relative decrease in the Ti and Cr content will reduce toughness and make chipping and fracture more likely to occur, while if it exceeds 0.65, high hardness cannot be obtained.

[0023] In addition, by setting the value of z to 0.90 or more, heat resistance is further improved and excellent wear resistance is exhibited. On the other hand, if the value of z exceeds 1.10, the residual stress in the hard coating layer becomes too large, resulting in a decrease in fracture resistance.

[0024] The average composition and average thickness of the (TiAlM)N coating and the (CrAlM)N coating can be determined by observing a cross section (a longitudinal cross section perpendicular to the surface of the tool substrate) using a scanning electron microscope (SEM), a transmission electron microscope (TEM), or energy dispersive X-ray spectroscopy (EDS).

[0025] Hard Coating Interfacial area of: In the coated tool of this embodiment, the average thickness (thickness) is in the range of 5 to 100 nm above the surface of the tool substrate toward the tool surface. Hard Coating In the interface region, the N content relative to the total amount of Ti, Al, M, and N, and the N content relative to the total amount of Cr, Al, M, and N, are both 10 to 30 atomic % on the surface side of the tool substrate (the point at which atoms related to the (Ti, Al, M, N) or (Cr, Al, M, N) coating composition are detected in the interface region from the surface side of the tool substrate toward the tool surface), and it is preferred that the N content (the N content relative to the total amount of Ti, Al, M, and N, and the N content relative to the total amount of Cr, Al, M, and N) increases from the surface of the tool substrate toward the tool surface.

[0026] This makes it difficult for the (TiAlM)N and (CrAlM)N coatings to decompose in the interface region with the tool substrate, where composition changes (decomposition) of the (TiAlM)N and (CrAlM)N coatings are likely to occur, and it is believed that cracks occurring near the interface region can be suppressed, resulting in improved adhesion between the tool substrate and the hard coating layer and improved cutting performance. The average thickness of the interface region is more preferably in the range of 20 to 80 nm. The N content in this interface region can be determined by TEM-EDS.

[0027] Tool base: Any conventionally known substrate for this type of tool substrate can be used as long as it does not impede the achievement of the object of the present invention. Examples of preferred substrates include cemented carbide (WC-based cemented carbide, WC, and those containing Co and carbonitrides of Ti, Ta, Nb, etc.), cermets (those mainly composed of TiC, TiN, TiCN, etc.), high-speed steel, ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cBN sintered compacts, and diamond sintered compacts.

[0028] Manufacturing method: The (TiAlM)N coating and (CrAlM)N coating in the coated tool of this embodiment can be produced using an arc ion plating (AIP) device, which is a type of PVD. Above The interface region having an average thickness in the range of 5 to 100 nm toward the tool surface can be formed by gradually increasing (for example, linearly increasing) the partial pressure of nitrogen gas, which is the atmospheric gas, from the start of film formation. [Example]

[0029] Next, examples will be described. The present invention is not limited to the examples. The following describes an example in which the present invention is applied to an insert cutting tool using a WC-based cemented carbide as the tool substrate. However, the same applies when the above-mentioned TiCN-based cermet or the like is used as the tool substrate, or when the present invention is applied to a drill, end mill, or the like as the tool.

[0030] First, Co powder, VC powder, Cr3C2 powder, TiC powder, TaC powder, NbC powder, and WC powder were prepared as raw material powders, and these raw material powders were blended according to the composition shown in Table 1. Wax was then added and the mixture was wet mixed in a ball mill for 72 hours, dried under reduced pressure, and then press-molded at a pressure of 100 MPa. Next, these powder compacts were sintered and machined to the specified dimensions to produce tool substrates 1 to 3 made of WC-based cemented carbide and having the insert shape of ISO standard SEEN1203AFTN1.

[0031] Next, to form a hard coating layer using an AIP device, tool substrates 1 to 3 were ultrasonically cleaned in acetone, dried, and mounted along the outer periphery at a predetermined radial distance from the central axis on a rotary table in the AIP device. A Ti-Al-M alloy target and a Cr-Al-M alloy target of a predetermined composition were also placed as cathode electrodes (evaporation sources). The Ti-Al-M alloy target and the Cr-Al-M alloy target of a predetermined composition were targets with compositions corresponding to the average compositions of the desired (TiAlM)N and (CrAlM)N coatings, respectively.

[0032] Next, evacuate the AIP device and -2While maintaining a vacuum of 100 Pa or less, the inside of the AIP device was heated to 500°C using a heater. The atmosphere was then set to 0.5 to 2.0 Pa, and a DC bias voltage of -200 to -1000 V was applied to the tool substrate, which was rotating on the rotating table. This resulted in a bombardment treatment of the surface of the tool substrate with argon ions or metal ions for 5 to 120 minutes. The metal ions were generated by passing a predetermined current in the range of 80 to 240 A between a cathode electrode (evaporation source) made of a metal target and an anode electrode, causing an arc discharge.

[0033] Nitrogen gas and Ar gas, with partial pressures in the range of 0.1 to 5.0 Pa shown in Tables 2 and 3, were introduced into the AIP device as reactive gases for a predetermined time. The furnace temperature was maintained at the same temperature shown in Tables 2 and 3. A DC bias voltage in the range of −30 to −150 V shown in Tables 2 and 3 was applied to the tool substrate rotating on the rotary table. Furthermore, a current in the range of 80 to 240 A shown in Tables 2 and 3 was applied between a cathode electrode (evaporation source) made of a Ti-Al-M alloy target or a Cr-Al-M alloy target and an anode electrode to generate an arc discharge. Thus, coated tools 1 to 9 and 11 to 19 (hereinafter referred to as "example tools") of the present invention shown in Tables 4 and 5 were fabricated.

[0034] In Tables 2 and 3, "N2 gas supply time (min) to interface region" refers to "N2 gas supply time (min) during interface region formation." The pressure, N2, and Ar volume % were linearly changed from the initial values ​​to the final values ​​over the "N2 gas supply time (min) to interface region region," and then film formation was completed with these final values.

[0035] For comparison, a (TiAlM)N coating was vapor-deposited on the tool substrates 1 to 3 under the conditions shown in Table 2 using the same AIP equipment as above, and a (CrAlM)N coating was vapor-deposited under the conditions shown in Table 3, to produce comparative coated tools 1 to 3 and 11 to 13 (4 to 10 are missing numbers) shown in Tables 6 and 7 (hereinafter referred to as "comparative example tools").

[0036] The average thickness, average composition, and N content in the interface region of the hard coating layers with (TiAlM)N and (CrAlM)N coatings were determined by cross-sectional observation using a scanning electron microscope (SEM), a transmission electron microscope (TEM), and energy dispersive X-ray spectroscopy (EDS). The observed cross section was a longitudinal section of the hard coating layer perpendicular to the surface of the tool substrate, with a width of 10 μm in the direction parallel to the surface of the tool substrate, and was set so as to include the entire thickness region of the hard coating layer.

[0037] Specifically, the average layer thickness was calculated by magnifying the observed cross section 5000 times and measuring the layer thickness at five points. The average composition and N content of the interface region were determined by EDS line analysis, which was performed at five equal intervals in the layer thickness direction. That is, five TEM-EDS line analyses were performed at equal intervals of 100 μm from the tool substrate side to the tool surface side.

[0038] And (Ti, Al, M, N) or (Cr, Al, M, N) Hard Coating The tool substrate-side position was determined as a point 0.5 nm from the point closest to the tool substrate surface where the atoms constituting the N content were detected and the N content was 10 to 30 atomic %. The tool surface-side position was also determined as a point 0.5 nm from the point where the N content no longer increased. These positions were measured from the tool substrate surface. Tables 4 to 7 show the N content at the tool substrate-side position and the tool surface-side position as the average of the five analyses. The average layer thickness of the interface region was calculated by adding 1 nm to the distance between the tool substrate-side position and the tool surface-side position.

[0039] [Table 1]

[0040] [Table 2]

[0041] [Table 3]

[0042] [Table 4]

[0043] [Table 5]

[0044] [Table 6]

[0045] [Table 7]

[0046] Next, high-speed cutting tests were carried out on alloy steel, cast iron, carbon steel, and stainless steel for Example Tools 1 to 9, 11 to 19 and Comparative Tools 1 to 3, 11 to 13 under the following conditions.

[0047] Cutting test A: (Tools 1 to 9 of this example, Tools 1 to 3 of the comparative example) Work material: JIS SCM430 (HB250) round bar Cutting speed: 220m / min. Cutting depth: 0.3mm Feed: 0.25mm / rev. Cutting time: 5 minutes High-speed cutting test of alloy steel under the conditions (normal cutting speed and feed are 165 m / min. and 0.20 mm / rev., respectively) The results of cutting test A are shown in Table 8.

[0048] Cutting test B: (Tools 1 to 9 of this example, Tools 1 to 3 of the comparative example) Work material: JIS FCD600 round bar Cutting speed: 220m / min. Cutting depth: 0.25mm Feed: 0.21mm / rev. Cutting time: 5 minutes High-speed cutting test of cast iron under the conditions (normal cutting speed and feed are 145 m / min. and 0.2 mm / rev., respectively) The results of cutting test B are shown in Table 9.

[0049] Cutting test C: (Tools 11 to 19 of this example, Tools 11 to 13 of the comparative example) Work material: JIS S55C (HB250) round bar Cutting speed: 220 m / min. Cutting depth: 0.2 mm Feed: 0.24mm / rev. Cutting time: 5 minutes, Continuous high-speed, high-feed cutting test of carbon steel under the conditions (normal cutting speed and feed are 145 m / min. and 0.25 mm / rev., respectively). The results of cutting test C are shown in Table 10.

[0050] Cutting test D: (Tools 11 to 19 of this example, Tools 11 to 13 of the comparative example) Work material: JIS SUS304 (HB180) round bar Cutting speed: 140m / min. Cutting depth: 2.0mm Feed: 0.33mm / rev. Cutting time: 9 minutes of Under the conditions Wet continuous high-feed cutting test of stainless steel (normal cutting speed and feed rate are 120 m / min. and 0.3 mm / rev., respectively) The results of cutting test D are shown in Table 11.

[0051] [Table 8]

[0052] [Table 9]

[0053] [Table 10]

[0054] [Table 11]

[0055] The results in Tables 8 to 11 show that Example Tools 1 to 9 did not experience any abnormal damage such as chipping or peeling in either Cutting Test A or B, and Example Tools 11 to 19 did not experience any abnormal damage such as chipping or peeling in either Cutting Test C or D, demonstrating excellent chipping resistance and wear resistance. In contrast, Comparative Tools 1 to 3 clearly experienced chipping or progressed flank wear in either Cutting Test A or B, and Comparative Tools 11 to 13 clearly experienced chipping or reached the end of their life in a short period of time in either Cutting Test C or D.

[0056] The above-disclosed embodiments are merely illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, not by the above-disclosed embodiments, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims. [Explanation of symbols]

[0057] 1: Tool base 2:Interfacial area 3: Hard coating 4: Hard coating layer

Claims

1. A surface-coated cutting tool comprising a tool substrate and a hard coating layer having an average thickness of at least 0.5 to 10.0 μm on a surface of the tool substrate, the hard coating layer including a composite nitride coating having an interface region on the surface side of the tool substrate, The composite nitride coating has the composition formula: (Ti １－ｘ―ｙ Al ｘ M ｙ ) N ｚ When expressed as above, the average composition satisfies 0.35≦x≦0.80, 0.00≦y≦0.20, 0.20≦(1−x−y)≦0.65, and 0.90≦z≦1.10 (where x, y, and z are atomic ratios, and M is at least one of an atom of Groups 4 to 6 of the IUPAC periodic table, Y, Si, La, and Ce), the interface region is located above the surface of the tool substrate and has an average thickness in the range of 5 to 100 nm toward the tool surface, and the content ratio of N to the total amount of Ti, Al, M, and N is 10 to 30 atomic % on the surface side of the tool substrate and increases from the surface side of the tool substrate toward the tool surface; A surface-coated cutting tool characterized by:

2. A surface-coated cutting tool comprising: a tool substrate; and a hard coating layer having an average thickness of 0.5 to 10.0 μm on a surface of the tool substrate, the hard coating layer including a composite nitride coating having an interface region on the surface side of the tool substrate, The composite nitride coating has the composition formula: (Cr １－ｘ―ｙ Al ｘ M ｙ ) N ｚ When expressed as above, the average composition satisfies 0.35≦x≦0.80, 0.00≦y≦0.20, 0.20≦(1−x−y)≦0.65, and 0.90≦z≦1.10 (where x, y, and z are atomic ratios, and M is at least one of an atom of Groups 4 to 6 of the IUPAC periodic table, Y, Si, La, and Ce), the interface region has an average thickness in the range of 5 to 100 nm above the surface of the tool substrate toward the tool surface, and the content ratio of N to the total amount of Cr, Al, M, and N is 10 to 30 atomic % on the surface side of the tool substrate and increases from the surface side of the tool substrate toward the tool surface; A surface-coated cutting tool characterized by:

Images