Surface coated cutting tools

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

[0002] Conventionally, coated tools have been known in which a coating layer is formed on a tool substrate such as a tungsten carbide (hereinafter referred to as WC)-based cemented carbide. Furthermore, it has been proposed that a coating layer with higher hardness can be obtained by adjusting the composition of this coating layer.

[0003] For example, Patent Document 1 describes a coated tool in which a boride film made of one or more metal elements selected from Al, Si, Cr, W, Ti, Nb, and Zr is coated on the surface of the tool substrate, the boride film has a hexagonal crystal structure, the 011 diffraction line has the strongest hardness in X-ray diffraction, and the residual compressive stress is 0.1 GPa or more, and the coated tool is said to have a long lifespan because it has excellent adhesion and a high-hardness film. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2008-238281 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] A coated tool having a boride film as a coating layer has excellent cutting performance because the coating layer has excellent adhesion and high hardness, as described in Patent Document 1, for example. However, the inventors have found that it lacks heat resistance when used for high-speed, high-efficiency cutting of difficult-to-machine materials such as Ti-based alloys.

[0006] The present invention aims to provide a coated tool with sufficient heat resistance and long lifespan, even when used for high-speed, high-efficiency cutting of difficult-to-machine materials such as Ti-based alloys. Here, high-speed, high-efficiency cutting refers to cutting processes in which the cutting speed is 30% or more faster and the amount of material removed is 30% or more greater than in normal cutting processes. [Means for solving the problem]

[0007] The inventors diligently conducted research to obtain a coated tool that achieves the above objective. As a result, they obtained a novel finding that if the coating layer contains a composite boride containing one or more lanthanides (hereinafter, lanthanides may be denoted as L) in addition to Ti, the coating layer will have sufficient heat resistance and a long service life, even when subjected to high-speed, high-efficiency cutting of difficult-to-machine materials such as Ti-based alloys.

[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 lanthanide with an average layer thickness of 0.5 to 10.0 μm, and the average composition of the composite boride layer is defined by the composition formula:Ti 1-z L z B x When expressed as (where L is one or more lanthanides), the atomic ratio z satisfies 0.01 to 0.20 and x satisfies 1.0 to 3.5. A cutting tool characterized by a surface coating. [Effects of the Invention]

[0009] According to the above, it exhibits excellent wear resistance and fracture resistance even when subjected to high-speed, high-efficiency cutting of difficult-to-machine materials such as Ti-based alloys. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of a longitudinal cross-section of the coating layer in the surface-coated cutting tool of the present invention. [Modes for carrying out the invention]

[0011] Hereinafter, the coating tool according to the embodiment of the present invention will be described in more detail. In the description of this specification and the claims, when a numerical range is expressed as "A to B", the range includes the numerical values of the upper limit (B) and the lower limit (A). Also, the upper limit (B) and the lower limit (B) are in the same unit.

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

[0013] 1. Coating layer Hereinafter, the coating layer will be described.

[0014] (1) Composition of the coating layer The coating layer in the coating tool according to the present embodiment has a composite boride layer of Ti and L, and optionally (if necessary), a lower layer may be provided below it and an upper layer may be provided above it.

[0015] (1-1) Composite boride layer of Ti and L The average composition of the composite boride layer of Ti and L is represented by the composition formula: Ti 1-z L z B x (L is one or more kinds of lanthanoids), when expressed as such, it is preferable that z is 0.01 to 0.20 and x is 1.0 to 3.5.

[0016] The reason why the above range of z is preferable is that when it is less than 0.01, the improvement in heat resistance and mechanical properties brought by L cannot be obtained, while when it exceeds 0.20, the hardness and toughness of the composite boride layer decrease, and chipping and defects are likely to occur. The reason why the above range of x is preferable is that when it is less than 1.0, the improvement in weld resistance of the composite boride phase cannot be fully exerted, while when it exceeds 3.5, the hardness of the composite boride phase decreases and wear progresses easily at an early stage.

[0017] (1-2) Average film thickness The average layer 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 long-term use. On the other hand, if it exceeds 10.0 μm, the crystal grains of the composite boride layer tend to coarsen, and improvement in chipping resistance cannot be obtained. The average layer thickness is more preferably 0.8 to 8.0 μm.

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

[0019] Here, the reason for setting the total average layer thickness of the lower layer within the above range is that if it is less than 0.1 μm, the function of the lower layer is not sufficiently exerted. On the other hand, if it exceeds 20.0 μm, the crystal grains of the lower layer tend to coarsen, and chipping is likely to occur in the coating layer.

[0020] (2-2) Upper layer As the upper layer, an aluminum oxide layer with an average layer thickness of 1.0 to 25.0 μm may be provided. By providing the upper layer, a coated tool that exhibits more excellent wear resistance and thermal stability can be obtained.

[0021] Here, the reason for setting the average layer thickness of the aluminum oxide layer within the above range is that if it is less than 1.0 μm, the function of the upper layer is not sufficiently exerted. On the other hand, if it exceeds 25.0 μm, the crystal grains of the upper layer tend to coarsen, and chipping is likely to occur in the coating layer.

[0022] Furthermore, a TiN layer may be provided as an upper layer. When this TiN layer is provided, the TiN layer itself has a golden hue, so it can be used as an identification layer to distinguish whether a coating tool is unused or used by the change in hue. The average thickness of this TiN layer used as an identification layer can be, for example, 0.1 to 1.0 μm.

[0023] 2. Method for 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 (in the case of an insert, a section perpendicular to the surface of the tool substrate when minute irregularities on the surface are ignored and it is treated as a flat surface; in the case of a shaft tool such as a drill, a section perpendicular to the shaft) using energy dispersive X-ray spectroscopy (EDS) attached to a scanning electron microscope (SEM) or transmission electron microscope (TEM).

[0024] Here, the surface of the tool substrate is determined by observing its longitudinal section and using elemental mapping to define the interface between the tool substrate and the composite boride layer of Ti and L (or the lower layer if one is provided). The average line of the roughness curve of this interface is then arithmetically calculated and defined as the surface of the tool substrate.

[0025] 3.Tool base (1)Material The tool substrate used in this embodiment can be any of the conventionally known tool substrate materials, as long as it does not hinder the achievement of the aforementioned objectives. For example, it is preferable to use any of the following: cemented carbide (WC-based cemented carbide, including those containing WC and Co, and further including those with carbonitrides such as Ti, Ta, and Nb added), cermet (mainly composed of TiC, TiN, TiCN, etc.), ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cBN sintered body, or diamond sintered body.

[0026] (2) Shape The shape of the tool substrate is not particularly limited as long as it is a shape used as a cutting tool, and examples thereof include the shape of an insert and the shape of a drill.

[0027] 4. Manufacturing Method The coating layer of the coated tool of the present embodiment can be manufactured, for example, using a film-forming apparatus having an evaporation source of high-power pulse sputtering, which is a type of PVD. Also, as the target, when providing the TiN layer as the lower layer, Ti or a TiAl target is used, and for the composite boride layer of Ti and L, Ti (1-z) L z B x When providing an aluminum oxide layer as the upper layer, an Al target can be used respectively to form a film.

Example

[0028] Next, examples will be described. Here, as an example of the coated tool of the present invention, an insert cutting tool using a WC-based cemented carbide as a tool substrate will be described. However, a tool substrate of the above-mentioned material can be used, and as described above, the same applies when applied to a drill, an end mill, etc. as the shape of the tool substrate.

[0029] First, as raw material powders, Co powder, TiC powder, VC powder, TaC powder, NbC powder, Cr3C2 powder, and WC powder are prepared. These raw material powders are blended according to the blending composition shown in Table 1, and further wax is added and wet-mixed in a ball mill for 72 hours. After drying under reduced pressure, they are press-molded at a pressure of 100 MPa, and these green compacts are sintered and processed to have a predetermined size, thereby producing tool substrates 1 to 3 made of WC-based cemented carbide having an insert shape of ISO standard SEEN1203AFTN1.

[0030] Next, in order to form a coating layer on tool substrates 1-3 using a film deposition apparatus equipped with a high-power sputtering deposition source and a DC sputtering deposition source, the tool substrates were ultrasonically cleaned in acetone and, in a dried state, mounted along their outer circumference at a predetermined radial distance from the central axis on a rotary table within the apparatus. In addition, Ti, Al, and alloy targets of Ti, L, and boron were placed as cathode electrodes (evaporation sources).

[0031] Next, the inside of the film deposition apparatus is evacuated and 10 -2 While maintaining a vacuum of less than Pa, the inside of the apparatus was heated to 500°C with a heater, then the atmosphere was set to Ar gas at 1.0 Pa, and a DC bias voltage of -1000V was applied to the tool substrate rotating on the rotary table, and the surface of the tool substrate was bombarded with argon ions for 30 minutes.

[0032] Ar gas with a partial pressure in the range of 0.1 to 1.0 Pa shown in Table 2 was introduced as a reaction gas into the film deposition apparatus for a predetermined time, and the furnace temperature was maintained at the same temperature as shown in Table 2. High-power pulse sputtering was performed on a tool base rotating on the rotary table under the predetermined pulse sputtering conditions shown in Table 2 for a time corresponding to the layer thickness, thereby producing the coating tools of the present invention (hereinafter referred to as "Examples") 1 to 9 shown in Table 2.

[0033] On the other hand, for comparison, coating layers were deposited onto the tool substrates 1 to 3 using the same film deposition apparatus as described above, under the conditions shown in Table 3, to produce the comparative example coated tools (hereinafter referred to as "comparative examples") 1 to 5 shown in Table 3.

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

[0035] Specifically, the average thickness of each layer was calculated by magnifying the observation cross-section (longitudinal section) 5000 times and determining the film thickness at five points. 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, single-edge face milling tests were performed on tools 1-9 of the present invention and comparative example tools 1-5 using a SE445R0506E cutter. Wet high-speed cutting tests were performed on Ti-6Al-4V alloy under the following cutting conditions.

[0040] Cutting conditions: Workpiece: Block material measuring 110mm in width and 250mm in length. Cutting speed: 105 m / min. Cut: 1.3 mm Feed rate: 0.12 mm / tooth. The cutting length was reduced to 1.8m, and the wear width of the flank surface was measured to observe the wear condition of the cutting edge. The results of the cutting test are shown in Table 4.

[0041] [Table 4]

[0042] According to the results in Table 4, no abnormal damage such as chipping or peeling occurred in Examples 1 to 9, indicating excellent abrasion resistance and chipping resistance. In contrast, it is clear that Comparative Examples 1 to 5 reach the end of their lifespan in a short 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 composite boride layer 4 Upper layer

Claims

1. 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 lanthanide with an average layer thickness of 0.5 to 10.0 μm, and the average composition of the composite boride layer is defined by the composition formula: Ti １－ｚ L ｚ B x When expressed as (where L is one or more lanthanides), the atomic ratio z satisfies 0.01 to 0.20 and x satisfies 1.0 to 3.

5. A surface-coated cutting tool characterized by the following features.

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