Surface-coated cutter

Abstract

To provide a coated tool that can be used in high-speed and high-efficiency cutting of hard-to-cut materials such as a Ti-based alloy and has its coating layer to exhibit sufficient heat resistance even in such treatment, demonstrating a long life.SOLUTION: A surface-coated cutter includes a tool substrate and a coating layer on the surface of the tool substrate. The coating layer includes a composite boride layer of Ti and lanthanoid with its average layer thickness of 0.5-10.0 μm. With the average composition of the composite boride layer expressed by the formula: Ti1-zLzBx (L is one or more lanthanoid elements), the atomic ratio z is 0.01-0.20 and x is 1.0-3.5.SELECTED DRAWING: Figure 1

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] 2. Description of the Related Art Conventionally, as a coated tool, for example, a tool having a coating layer formed on a tool substrate such as a tungsten carbide (hereinafter abbreviated as WC)-based cemented carbide or the like has been known. It has been proposed to obtain a coating layer with higher hardness by adjusting the composition of the coating layer.

[0003] For example, Patent Document 1 describes a coated tool in which the surface of a tool substrate is coated with a boride coating made of one or more metallic elements selected from Al, Si, Cr, W, Ti, Nb and Zr, the boride coating having a hexagonal crystal structure, the 011 diffraction line having the greatest hardness in X-ray diffraction, and a residual compressive stress of 0.1 GPa or more. The coated tool is said to have a long life due to the presence of a coating with excellent adhesion and high hardness. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-238281 A Summary of the Invention [Problem to be solved by the invention]

[0005] As described in Patent Document 1, for example, a coated tool having a boride coating as a coating layer has excellent cutting performance because the coating layer has excellent adhesion and high hardness. However, according to the inventors' investigations, it has been found that the heat resistance of the coated tool is insufficient when used for high-speed, high-efficiency cutting of difficult-to-cut materials such as Ti-based alloys.

[0006] The present invention aims to provide a coated tool having a long life and a coating layer that has sufficient heat resistance even when subjected to high-speed, high-efficiency cutting of difficult-to-cut materials such as Ti-based alloys. High-speed, high-efficiency cutting is defined as cutting in which the cutting speed is 30% or more faster and the cutting amount is 30% or more greater than that of normal cutting. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to obtain a coated tool that achieves the above-mentioned object, and as a result have made a new discovery that when a coating layer contains a composite boride that contains one or more lanthanoids (hereinafter, lanthanoids may be abbreviated as L) in addition to Ti, the coating layer has sufficient heat resistance even when used for high-speed, high-efficiency cutting of difficult-to-cut materials such as Ti-based alloys, resulting in a coated tool with a long life.

[0008] The present invention is based on this finding and is as follows. "A surface-coated cutting tool having a tool base and a coating layer on the surface of the tool base, The coating layer includes a composite boride layer of Ti and a lanthanoid having an average layer thickness of 0.5 to 10.0 μm, and the average composition of the composite boride layer is represented by the formula: Ti 1-z L z B x (L is one or more lanthanides), the atomic ratio z is 0.01 to 0.20 and x is 1.0 to 3.5. A surface-coated cutting tool characterized by the above. Effect of the Invention

[0009] According to the above, even when used in high-speed, high-efficiency cutting of difficult-to-cut materials such as Ti-based alloys, excellent wear resistance and chipping resistance are exhibited. [Brief description of the drawings]

[0010] [Figure 1] 2 is a schematic diagram of a vertical cross section of a coating layer in the surface-coated cutting tool of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The coated tool according to the embodiment of the present invention will be described in more detail below. In the present specification and claims, when a numerical range is expressed using "A to B", the range includes the numerical values ​​of the upper limit (B) and the lower limit (A). The upper limit (B) and the lower limit (B) are expressed in the same unit.

[0012] The layer structure of the coating layer of the coated tool according to the embodiment of the present invention is as shown typically in FIG. 1, and includes a tool substrate (1) on which a composite boride layer (3) of Ti and lanthanoid is formed. A lower layer (2) may be provided between the boride layer (3) and the tool substrate (1), and an upper layer (4) may be provided on the upper portion of the boride layer.

[0013] 1.Coating layer The coating layer will now be described.

[0014] (1) Composition of the coating layer The coating layer in the coated tool according to this embodiment has a composite boride layer of Ti and L, and may optionally (if necessary) have a lower layer thereunder and an upper layer thereon.

[0015] (1-1) Ti and L composite boride layer The average composition of the Ti and L composite boride layer is 1-z L z B x (L is one or more lanthanoids), z is preferably 0.01 to 0.20 and x is preferably 1.0 to 3.5.

[0016] The reason why the above range of z is preferable is that if it is less than 0.01, the improvement in heat resistance and mechanical properties brought about by L cannot be obtained, while if it exceeds 0.20, the hardness and toughness of the composite boride layer decrease, making chipping and breakage more likely to occur. The reason why the above range of x is preferable is that if it is less than 1.0, the improvement in the welding resistance of the composite boride phase cannot be fully demonstrated, while if it exceeds 3.5, the hardness of the composite boride phase decreases and wear tends to progress early.

[0017] (1-2) Average film thickness The average thickness of the composite boride layer of Ti and L is preferably 0.5 to 10.0 μm. The reason is that if it is less than 0.5 μm, the composite boride layer cannot exhibit excellent wear resistance over a long period of use, while if it exceeds 10.0 μm, the crystal grains of the composite boride layer tend to become coarse, and improvement in chipping resistance cannot be obtained. The average thickness is more preferably 0.8 to 8.0 μm.

[0018] (2-1) Lower layer A sublayer may be provided between the tool substrate and the Ti-L composite boride layer. The lower layer is made of one or more layers selected from a Ti or TiAl carbide layer, a nitride layer, a carbonitride layer, a carbonate layer and a carbonitride layer so as to have a total average layer thickness of 0.1 to 20.0 μm. When this lower layer is provided, in combination with the functions of the layers constituting the lower layer, the coated tool can exhibit even better wear resistance and chipping resistance.

[0019] The reason for setting the total average layer thickness of the lower layers within the above range is that if it is less than 0.1 μm, the function of the lower layers is not fully performed, while if it exceeds 20.0 μm, the crystal grains of the lower layers tend to become coarse, making the coating layer more susceptible to chipping.

[0020] (2-2) Upper layer The upper layer may be an aluminum oxide layer having an average thickness of 1.0 to 25.0 μm. By providing the upper layer, it is possible to obtain a coated tool that exhibits even better wear resistance and thermal stability.

[0021] The reason for setting the average thickness of the aluminum oxide layer within the above range is that if it is less than 1.0 μm, the upper layer does not function sufficiently, while if it exceeds 25.0 μm, the crystal grains in the upper layer tend to become coarse, making the coating layer more susceptible to chipping.

[0022] A TiN layer may be provided as the upper layer. In the case where the TiN layer is provided, the TiN layer itself has a golden color tone, and therefore, for example, it can be used as an identification layer that can distinguish whether the coated tool is unused or used by a change in color tone. The average thickness of the TiN layer as the identification layer may be, for example, 0.1 to 1.0 μm.

[0023] 2.Method of measuring average layer thickness In this embodiment, the average thickness of each layer constituting the coating layer can be determined by observing a longitudinal section (a section perpendicular to the surface of the tool base when the surface is treated as a flat surface, ignoring minute irregularities on the surface of the tool base, in the case of an insert; a section perpendicular to the axis in the case of an axial tool such as a drill) using Energy Dispersive X-ray Spectroscopy (EDS) attached to a Scanning Electron Microscopy (SEM) or a Transmission Electron Microscope (TEM).

[0024] Here, the surface of the tool base is observed in longitudinal section, and the interface between the tool base and the composite boride layer of Ti and L (or the lower layer, if a lower layer is provided) is determined by element mapping. For the roughness curve of the interface thus obtained, the average line is arithmetically determined, and this is regarded as the surface of the tool base.

[0025] 3.Tool base (1)Material The tool substrate used in this embodiment may be any of the materials of the conventionally known tool substrates, as long as they do not impede the achievement of the above-mentioned object. For example, it is preferable to use any of the following: cemented carbide (WC-based cemented carbide, WC, Co, and Ti, Ta, Nb, etc.), cermet (TiC, TiN, TiCN, etc.), ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cBN sintered body, and diamond sintered body.

[0026] (2) Shape There are no particular limitations on the shape of the tool body as long as it is a shape that can be used as a cutting tool, and examples of the shape include the shape of an insert and the shape of a drill.

[0027] 4. Manufacturing method The coating layer of the coated tool of this embodiment can be manufactured, for example, by using a deposition device having a deposition source of high-power pulse sputtering, which is a type of PVD. In addition, as the target, when forming the TiN layer as the lower layer, a Ti or TiAl target is used, and when forming the composite boride layer of Ti and L, a Ti (1-z) L z B x When an aluminum oxide layer is to be formed as the upper layer, an Al target is used. EXAMPLES

[0028] Next, an embodiment will be described. Here, as an example of the coated tool of the present invention, we will describe an insert cutting tool that uses a WC-based cemented carbide as the tool base. However, the tool base can be made of any of the materials described above, and the same applies when the tool base is in the shape of a drill, end mill, etc., as described above.

[0029] First, Co powder, TiC powder, VC powder, TaC powder, NbC powder, Cr3C2 powder, and WC powder were prepared as raw material powders. These raw material powders were mixed according to the composition shown in Table 1, and wax was added and wet mixed in a ball mill for 72 hours. The mixture was then dried under reduced pressure and pressed at a pressure of 100 MPa. These powder compacts were sintered and processed to the specified dimensions to produce tool bases 1 to 3 made of WC-based cemented carbide having an insert shape conforming to ISO standard SEEN1203AFTN1.

[0030] Next, in order to form a coating layer on the tool substrates 1 to 3 using a film-forming device having a high-power sputtering deposition source and a direct current (DC) sputtering deposition source, the tool substrates were ultrasonically cleaned in acetone and, in a dried state, mounted along the outer periphery at a position radially away from the central axis on a rotating table in the device by a predetermined distance. In addition, targets of Ti, Al, and an alloy of Ti, L, and boron were placed as cathode electrodes (evaporation sources).

[0031] Next, the inside of the deposition apparatus was evacuated and -2 While maintaining a vacuum of less than 1.0 Pa, the inside of the apparatus was heated to 500°C using a heater, and then the Ar gas atmosphere was set to 1.0 Pa. A DC bias voltage of -1000 V was applied to the tool base rotating on the turntable, and the surface of the tool base was bombarded with argon ions for 30 minutes.

[0032] Ar gas having a partial pressure in the range of 0.1 to 1.0 Pa shown in Table 2 was introduced into the film-forming apparatus as a reactive gas for a predetermined period of time, while the furnace temperature was maintained at the same temperature shown in Table 2. The tool substrate rotating on the turntable was subjected to high-power pulse sputtering under the predetermined pulse sputtering conditions shown in Table 2 for a period of time corresponding to the layer thickness, to produce coated tools 1 to 9 of the present invention shown in Table 2 (hereinafter referred to as "Examples")

[0033] On the other hand, for comparison, a coating layer was vapor-deposited on the tool bases 1 to 3 using the same film-forming apparatus as above under the conditions shown in Table 3, and coated tools 1 to 5 of the comparative examples (hereinafter referred to as "comparative examples") shown in Table 3 were produced.

[0034] The average thickness and average composition of the coating layer were determined by cross-sectional observation using a scanning electron microscope (SEM), a transmission electron microscope (TEM), and energy dispersive X-ray spectroscopy (EDS) for longitudinal sections of the coating layer perpendicular to the surface of the tool base of Examples 1 to 9 and Comparative Examples 1 to 5 prepared above, with a field of view set to include the entire thickness region of the coating layer and with a width of 10 μm in the direction parallel to the surface of the tool base.

[0035] Specifically, the average thickness of each layer was calculated by measuring the film thickness at five points on the cross section (longitudinal section) enlarged by 5000 times. The average content of each component in each layer was determined by performing five TEM-EDS line analyses in the thickness direction.

[0036] [Table 1]

[0037] [Table 2]

[0038] [Table 3]

[0039] Next, a single-edged face milling test was performed using an SE445R0506E cutter on the tools 1 to 9 of the present invention and the comparative tools 1 to 5. A wet high-speed cutting test was performed on a Ti-6Al-4V alloy under the following cutting conditions.

[0040] Cutting conditions: Workpiece: Block material 110mm wide x 250mm long Cutting speed: 105 m / min. Cutout: 1.3 mm Feed: 0.12 mm / tooth. The cutting length was 1.8 m, the flank wear width was measured, and the wear state of the cutting edge was observed. The results of the cutting tests are shown in Table 4.

[0041] [Table 4]

[0042] The results in Table 4 show that, for Examples 1 to 9, no abnormal damage such as chipping or peeling occurred, and both the wear resistance and chipping resistance were excellent. In contrast, it is clear that Comparative Examples 1 to 5 reach the end of their life in a short period of time due to the occurrence of chipping or the progression of flank wear. [Explanation of symbols]

[0043] 1 Tool base 2. Lower layer 3. Ti and lanthanide complex boride layer 4 Upper layer

Claims

1. A surface-coated cutting tool having a tool substrate and a coating layer on a surface of the tool substrate, The coating layer includes a composite boride layer of Ti and a lanthanoid having an average layer thickness of 0.5 to 10.0 μm, and the average composition of the composite boride layer is represented by the formula: Ti １－ｚ L ｚ B x (L is one or more lanthanoids), the atomic ratio z is 0.01 to 0.20 and x is 1.0 to 3.

5. A surface-coated cutting tool comprising:

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