Carbide tool and method for manufacturing the same

Abstract

The objective is to provide cemented carbide tools and their manufacturing methods that improve the adhesion and wear resistance of the hard coating while simplifying the manufacturing process and suppressing changes in the properties of the cemented carbide base material. [Solution] In a cemented carbide tool 1 in which a hard coating 20 is applied to the surface of a cemented carbide base material 10, the hard coating 20 comprises a lower layer 21 which is a metal nitride containing Al and Ti, an intermediate layer 22 which is a metal nitride containing elements selected from the group Al, Cr, Ti, and Si, and an upper layer 23 which is a metal oxynitride containing Al, Cr, and Ti, wherein the intermediate layer 22 is formed from a first intermediate layer 22A which is a metal nitride containing Al and Cr, and a second intermediate layer 22B which is a metal nitride containing Ti and Si.

Description

Technical Field

[0001] The present invention relates to a cemented carbide tool having a surface coated with a hard film and a method for manufacturing the same.

Background Art

[0002] Conventionally, cemented carbide tools have been widely used in applications such as cutting tools and molds because of their high hardness and wear resistance. In particular, attempts have been made to further improve wear resistance by forming a hard film on the surface of the tool. For example, methods for forming a film of compounds such as titanium carbide (TiC) and titanium nitride (TiN) are known. However, these films are prone to oxidation and peeling under high-temperature environments, which may lead to a reduction in tool life.

[0003] Patent Document 1 discloses a method of performing a specific surface pretreatment to improve the adhesion of a hard film, but this method requires a plurality of steps and has the problem of increasing manufacturing costs. In addition, Patent Document 2 discloses a technique for forming a hard film with a multilayer structure using a chemical vapor deposition (CVD) method, but since the film formation temperature is high, there has been concern about changes in the properties of the cemented carbide base material. Furthermore, in conventional methods, an intermediate layer or a special surface treatment can also be used to enhance the adhesion of the hard film.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problem to be Solved by the Invention

[0005] However, these methods have been criticized for complicating the manufacturing process and increasing costs. Patent Document 1 proposes using a special binder to improve the adhesion strength of the hard coating, but this may impose limitations on the thickness and uniformity of the hard coating.

[0006] Furthermore, while the technology described in Patent Document 2 employs a specific laminated structure to improve the wear resistance of the hard coating, it has the problem that temperature control during manufacturing is difficult, making it difficult to achieve highly reproducible manufacturing.

[0007] Therefore, the object of the present invention is to provide a cemented carbide tool and a method for manufacturing the same that can improve the adhesion and wear resistance of the hard coating while simplifying the manufacturing process and suppressing changes in the properties of the cemented carbide base material. [Means for solving the problem]

[0008] To solve the aforementioned problems, the cemented carbide tool of the first invention according to the present invention is a cemented carbide tool in which a hard coating is applied to the surface of a cemented carbide base material, wherein the hard coating comprises a lower layer which is a metal nitride containing Al and Cr, an intermediate layer which is a metal nitride containing Al, Cr, Ti and Si, and an upper layer which is a metal oxynitride containing Al, Cr and Ti, and the intermediate layer comprises a first intermediate layer which is a metal nitride containing Al and Cr, and a second intermediate layer which is a metal nitride containing Ti and Si.

[0009] Furthermore, the cemented carbide tool of the second invention is a cemented carbide tool in which a hard coating is applied to the surface of a cemented carbide base material, wherein the hard coating comprises a lower layer which is a metal nitride containing Al and Cr, an intermediate layer which is a metal nitride containing Al, Cr, Ti and Si, an upper layer which is a metal nitride containing Al, Cr and Ti, and an uppermost layer which is a metal oxynitride containing Al, Cr and Ti, and the intermediate layer comprises a first intermediate layer which is a metal nitride containing Al and Cr, and a second intermediate layer which is a metal nitride containing Ti and Si. The intermediate layer may further comprise a third intermediate layer which is a metal nitride containing Al and Ti, and the third intermediate layer may be laminated between the upper layer and the first intermediate layer, or between the first intermediate layer and the second intermediate layer.

[0010] The invention relating to a method for manufacturing cemented carbide tools comprises: a first step of coating the surface of a cemented carbide base material with a hard film which is a nitride containing Ti; a second step of forming a Ti-containing oxide film and a Ti-containing oxynitride film by heat-treating the cemented carbide in a reduced-pressure and oxidizing atmosphere after the first step; and a third step of removing the Ti-containing oxide film by heat-treating the cemented carbide in a reduced-pressure atmosphere after the second step. The second and third steps are considered as one unit, and the steps of this unit can be repeated multiple times. [Effects of the Invention]

[0011] The cemented carbide tool of the present invention has a multilayer hard coating consisting of a lower layer, an intermediate layer, and an upper layer, thereby improving wear resistance and heat resistance and extending its lifespan. Furthermore, by dividing the intermediate layer into a first intermediate layer and a second intermediate layer, the adhesion of the coating is improved, and peeling during use is suppressed. In addition, in the second invention, by forming a metal oxynitride in the uppermost layer, durability in an oxidizing atmosphere is improved, making it applicable to a wider range of processing environments.

[0012] Furthermore, the invention of a method for manufacturing cemented carbide tools optimizes the crystal structure of the hard coating and improves its mechanical properties by performing heat treatment in a reduced-pressure atmosphere and an oxidizing atmosphere after the formation of the hard coating. In particular, repeating the heat treatment process multiple times promotes the densification of the hard coating, resulting in further improvements in durability and wear resistance. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic cross-sectional view of the hard coating 20 in the cemented carbide tool 1 of the first embodiment. [Figure 2] This is a schematic cross-sectional view of the hard coating 40 in the cemented carbide tool 2 of the second embodiment. [Modes for carrying out the invention]

[0014] Details of a cemented carbide tool according to the first embodiment of the present invention will be described with reference to the drawings. Figure 1 shows a schematic cross-sectional view of a hard coating 20 applied to a cemented carbide base material 10. The cemented carbide tool 1 according to the first embodiment of the present invention is a cemented carbide tool 1 in which a hard coating 20 is applied to the surface of a cemented carbide base material 10. The hard coating 20 is broadly formed from a lower layer 21, an intermediate layer 22, and an upper layer 23, in order from the cemented carbide 10 side.

[0015] The lower layer 21 is a hard coating of metal nitride (AlCrN) containing Al and Cr, the intermediate layer 22 is a hard coating of metal nitride containing Al, Cr, Ti, and Si, and the upper layer 23 is a hard coating of metal oxynitride (AlCrTiNxOy:x+y=1) containing Al, Cr, and Ti. The intermediate layer 22 is formed from a first intermediate layer 22A, which is a metal nitride containing Al and Cr, and a second intermediate layer 22B, which is a metal nitride containing Ti and Si. The details of the lower layer, intermediate layer (first intermediate layer and second intermediate layer), and upper layer will be described below.

[0016] <Lower layer 21: AlCrN> The underlying layer that forms part of the hard coating of the cemented carbide tool of this invention is composed of a metal nitride (AlCrN) mainly composed of aluminum (Al) and chromium (Cr). This layer adheres closely to the surface of the cemented carbide base material and plays a role in improving wear resistance and heat resistance. In particular, oxidation resistance is improved as the Al content increases, and toughness is strengthened when the Cr content is high, so a well-balanced composition design is required. To improve durability under friction and high-temperature environments, AlCrN is uniformly formed using film deposition technologies such as PVD (physical vapor deposition) and CVD (chemical vapor deposition).

[0017] <Middle class 22> The intermediate layer consists of two metal nitride layers with different properties, and is responsible for stress distribution between the aforementioned lower layer (AlTiN) and the upper layer (AlCrTiNxOy:x+y=1), which will be described later. This improves the overall durability of the coating and reduces the risk of delamination during use.

[0018] (First intermediate layer 22A: AlCrN) The first intermediate layer is a metal nitride (AlCrN) containing aluminum (Al) and chromium (Cr), which contributes particularly to improved oxidation resistance and high-temperature hardness. The addition of Cr improves durability in oxidizing environments and ensures stability at high temperatures. While hardness improves with increasing Al content, excessive Al addition leads to brittleness, so it is desirable to adjust the composition to an appropriate ratio. AlCrN is a material that combines mechanical strength and wear resistance in a good balance, making it suitable for cutting tools and mold applications.

[0019] (Second intermediate layer 22B: TiSiN) The second intermediate layer is composed of a metal nitride (TiSiN) containing titanium (Ti) and silicon (Si), and provides high hardness and low friction characteristics. In particular, excellent wear resistance is achieved by dispersing Si as a fine nanocrystalline structure. TiSiN has a higher surface hardness than conventional TiN and exhibits extremely high wear resistance. Additionally, the addition of Si improves oxidation resistance, allowing it to exhibit excellent performance even in high-temperature environments. The presence of this layer improves the adhesion of the overall coating, and a longer service life can be expected.

[0020] <Upper layer 23: AlCrTiNxOy: x+y=1> The upper layer is composed of a metal oxynitride (AlCrTiNxOy: x+y=1) containing aluminum (Al), chromium (Cr) and titanium (Ti), and is primarily intended to improve oxidation resistance and lubricity. This layer contains oxygen (O), which greatly enhances durability in oxidizing environments. In particular, it suppresses oxidative wear during high-temperature cutting, contributing to extending the service life of tools. Furthermore, this layer also has the effect of reducing the surface friction coefficient, and plays a role in preventing welding with the workpiece by suppressing heat generation during cutting processing. The AlCrTiNxOy layer maximizes its performance particularly in cutting tools and wear-resistant parts used in high-temperature environments.

[0021] Next, a cemented carbide tool according to a second embodiment of the present invention will be described with reference to the drawings. A schematic cross-sectional view of a hard coating 40 coated on a cemented carbide base material 30 is shown in Figure 2. The cemented carbide tool 2 of the second embodiment is a cemented carbide tool 2 in which a hard coating 40 is coated on the surface of a cemented carbide base material 30, wherein the hard coating 40 comprises a lower layer 41 that is a metal nitride containing Al and Cr, an intermediate layer 42 that is a metal nitride containing Al, Cr, Ti and Si, an upper layer 43 that is a metal nitride containing Al, Cr and Ti, and an uppermost layer 44 that is a metal oxynitride containing Al, Cr and Ti.

[0022] The intermediate layer 42 comprises a first intermediate layer 42A, which is a metal nitride containing Al and Cr, and a second intermediate layer 42B, which is a metal nitride containing Ti and Si. The intermediate layer may further include a third intermediate layer 42C, which is a metal nitride containing Al and Ti. The details of the lower layer, intermediate layers (first to third intermediate layers), upper layer, and top layer will be described below.

[0023] <Lower layer 41:AlCrN> The underlying layer that forms part of the hard coating of the cemented carbide tool of the present invention is composed of a metal nitride containing Al (aluminum) and Cr (chromium). This underlying layer has high hardness and oxidation resistance, and also plays a role in improving adhesion to the cemented carbide base material. Furthermore, by adjusting the film thickness appropriately, the adhesion with the intermediate layer and upper layer described later is optimized, improving the overall durability of the coating.

[0024] <Middle class 42> The intermediate layer consists of three metal nitride layers with different properties, and is responsible for stress distribution between the aforementioned lower layer (AlCrN) and the upper layer (AlCrTiN), which will be described later. This improves the overall durability of the coating and reduces the risk of peeling during use.

[0025] (First intermediate layer 42A: AlCrN) The first intermediate layer, like the lower layer, is composed of a metal nitride containing Al and Cr, but the Al content has been increased to provide higher wear resistance and toughness. This layer ensures adhesion to the lower layer through strengthened chemical bonds and plays a role in dispersing stress throughout the intermediate layer through its crystalline structure.

[0026] (Second intermediate layer 42B: TiSiN) The second intermediate layer is composed of a metal nitride containing Ti (titanium) and Si (silicon), possessing high hardness and wear resistance. In particular, the inclusion of Si forms a fine nanocrystalline structure, improving oxidation resistance and high-temperature stability. This layer extends tool life and ensures stable performance even under harsh cutting environments.

[0027] (Third intermediate layer 42C: AlTiN) The third intermediate layer is composed of a metal nitride containing Al and Ti, and exhibits excellent heat resistance and wear resistance. In particular, it has the effect of improving oxidation resistance in high-temperature environments, maintaining the performance of the hard coating even after prolonged use. Furthermore, it improves the adhesion between the first intermediate layer and the upper layer, reducing the risk of delamination.

[0028] <Top layer 43: AlCrTiN> The upper layer is composed of a metal nitride containing Al, Cr, and Ti, providing high wear resistance and heat resistance. This layer absorbs stress dispersed in the intermediate layer while acting as a protective layer against external wear. Furthermore, the inclusion of Ti improves toughness, enhancing the impact resistance of the cutting tool.

[0029] <Top layer 44:AlCrTiNxOy:x+y=1> The top layer is composed of a metal oxynitride containing Al, Cr, and Ti, which significantly improves oxidation resistance and wear resistance. By incorporating an appropriate amount of oxygen into this top layer, surface lubricity is improved, reducing friction during cutting. Furthermore, it is expected to suppress thermal effects during machining, extending tool life.

[0030] Next, the details of the method for manufacturing cemented carbide tools described above will be explained. The method for manufacturing cemented carbide tools according to the present invention consists of three steps: a first step of coating the surface of the cemented carbide base material with a hard film which is a nitride containing Ti; a second step of heat-treating the cemented carbide after the first step in a reduced-pressure and oxidizing atmosphere; and a third step of heat-treating the cemented carbide after the second step in a reduced-pressure atmosphere. The details of the first to third steps will be explained below for each step.

[0031] <Step 1: Coating with a hard film> In the first step, a hard coating composed of titanium (Ti) nitride is applied to the surface of the cemented carbide base material. Physical vapor deposition (PVD) or chemical vapor deposition (CVD) can be used for the coating. This improves the wear resistance and heat resistance of the base material, enhancing its basic performance as a tool. The coating thickness can be optimized within a range of several micrometers to tens of micrometers depending on the application.

[0032] <Step 2: Heat treatment under an oxidizing atmosphere> In the second step, the cemented carbide coated with a hard film in the first step is heat-treated under a reduced-pressure and oxidizing atmosphere. This heat treatment adjusts the crystalline structure of the oxide film (titanium oxide) and reduces the internal stress of the hard film. Furthermore, by utilizing an oxidizing atmosphere, a fine oxide film and oxynitride film are formed on the surface, improving oxidation resistance and heat resistance. The heat treatment temperature and time are appropriately set according to the characteristics of the coating material used.

[0033] <Step 3: Heat treatment under reduced pressure> In the third step, the cemented carbide alloy from the second step is heat-treated again in a reduced-pressure atmosphere and an oxygen-free atmosphere (non-oxidizing atmosphere). By treating in a non-oxidizing atmosphere in this third step, the oxide film formed in the second step is permeated and diffused in a solid solution state, causing the oxide film (titanium oxide) to disappear and leaving the oxynitride film. In other words, it is expected that brittleness due to oxidation will be suppressed and the lifespan of the hard coating will be extended. The treatment conditions for this step are also adjusted as appropriate according to the characteristics and purpose of the hard coating.

[0034] <Repeat process: Additional steps> The second and third steps constitute one unit, and by repeating this unit multiple times, the properties of the hard coating can be further improved. Repeated processing promotes the refinement of the crystal grains of the hard coating, improving wear resistance and heat resistance. In addition, since the internal stress of the hard coating is made uniform with each heat treatment step, a highly durable cemented carbide tool that is resistant to peeling can be obtained. The number of repetitions is optimized according to the application and the required performance. [Explanation of symbols]

[0035] 1,2 Carbide alloy tools 10,30 Carbide alloy 20,40 Hard coating 21,41 lower layer 22,42 Middle class 22A,42A 1st intermediate layer 22B,42B 2nd middle layer 42C 3rd middle layer 23,43 upper layer 44 Top floor

Claims

1. A cemented carbide tool is characterized in that a hard coating is applied to the surface of a cemented carbide base material, wherein the hard coating comprises a lower layer which is a metal nitride containing Al and Cr, an intermediate layer which is a metal nitride containing an element selected from the group Al, Cr, Ti and Si, and an upper layer which is a metal oxynitride containing Al, Cr and Ti, and the intermediate layer comprises a first intermediate layer which is a metal nitride containing Al and Cr, and a second intermediate layer which is a metal nitride containing Ti and Si.

2. A cemented carbide tool is characterized in that a hard coating is applied to the surface of a cemented carbide base material, wherein the hard coating comprises a lower layer which is a metal nitride containing Al and Cr, an intermediate layer which is a metal nitride containing an element selected from the group Al, Cr, Ti and Si, an upper layer which is a metal nitride containing Al, Cr and Ti, and an uppermost layer which is a metal oxynitride containing Al, Cr and Ti, and the intermediate layer comprises a first intermediate layer which is a metal nitride containing Al and Cr, and a second intermediate layer which is a metal nitride containing Ti and Si.

3. The cemented carbide tool according to claim 2, characterized in that the intermediate layer further comprises a third intermediate layer which is a metal nitride containing Al and Ti, and is laminated between the upper layer and the first intermediate layer, or between the first intermediate layer and the second intermediate layer.

4. A method for manufacturing a cemented carbide tool, comprising: a first step of coating the surface of a cemented carbide base material with a hard film which is a nitride containing Ti; a second step of heat-treating the cemented carbide after the first step in a reduced-pressure atmosphere and an oxidizing atmosphere to form an oxide film containing Ti and an oxynitride film containing Ti; and a third step of heat-treating the cemented carbide after the second step in a reduced-pressure atmosphere to remove the oxide film.

5. The method for manufacturing a cemented carbide tool according to claim 4, characterized in that the steps of the second and third steps are considered as one unit, and the steps of the unit are repeated multiple times.

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