JP6498074B2 - Cemented carbide - Google Patents

Description

  The present invention relates to a cemented carbide, and more particularly to a cemented carbide suitable for forming a diamond coating.

  Cemented carbides such as WC-Co containing a carbide hard phase and a binder phase containing Co are used for various members such as cutting tools and chuck jigs because of their high hardness and excellent wear resistance. . In order to further improve the wear resistance and durability, a member is known in which the surface of a base material made of a cemented carbide is coated with a diamond film. However, Co contained in the binder phase can serve as a catalyst for producing graphite, which is an allotrope of diamond, so even if diamond is vapor-phase synthesized and coating of the substrate is attempted, graphite is produced exclusively on the surface of the substrate. End up. Therefore, there is a technique of forming a diamond film after silicifying Co present on the surface of the base material to form a silicide (Patent Document 1).

International Publication No. 2005/121398

  However, in the above-described conventional technique, there is a problem that the process of forming the coating becomes complicated because the process of converting Co present on the surface of the base material into silicide is required.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a cemented carbide capable of simplifying the process of forming a coating film.

Means for Solving the Problems and Effects of the Invention

In order to achieve this object, according to the cemented carbide according to claim 1, a hard phase mainly composed of WC particles, a binder phase mainly composed of Co binding the hard phase, and Cr, Nb, Zr, V And one or more elements selected from Ti. The WC particles are substantially composed of fine particles having an average particle diameter of 0.4 μm to 0.6 μm measured by the Fisher method and coarse particles having an average particle diameter of 1.2 μm to 1.4 μm measured by the Fisher method. Configured. Since the mass ratio of fine particles and coarse particles is fine particles / coarse particles = 25/75 to 15/85, fine WC particles enter the gaps between the coarse WC particles, and the WC particles can be densely arranged. Since the element content is 0.09% by mass to 0.9% by mass, the grain growth of the WC particles can be suppressed and the particle size of the densely arranged WC particles can be easily maintained. Since the content of Co binding WC particles is 0.7% by mass to 1.7 % by mass, the amount of Co exposed on the surface can be reduced. Since the amount of Co on the surface that can serve as a catalyst can be reduced, a desired film made of diamond can be formed on the surface. Since the process of converting the Co present on the surface into silicide is not required, there is an effect that the process of forming the film can be simplified.

  Since the cemented carbide according to claim 2 contains 0.09% by mass to 0.9% by mass of Ta, in addition to the effect of claim 1, there is an effect that the oxidation resistance can be improved.

  Hereinafter, preferred embodiments of the present invention will be described. The cemented carbide is a WC-based cemented carbide containing a hard phase mainly composed of WC particles. The hard phase is substantially composed of WC particles alone or substantially from WC particles and compound particles. When the hard phase is substantially composed only of WC particles, the cemented carbide is excellent in heat crack resistance, toughness, and strength. “Substantially constituted” means that the constituent elements are in solid solution except for inevitable impurities.

The hard phase compound particles are particles of a compound (excluding WC) of at least one metal selected from Group 4a, 5a, and 6a elements of the periodic table and at least one of carbon and nitrogen, that is, the above metal These are particles of one or more compounds selected from carbides (except WC), nitrides, carbonitrides, and solid solutions thereof. For example, TaC, (Ta, Nb) C, VC, Cr ₃ C ₂ , NbC, TiCN and the like can be mentioned. When the hard phase is substantially composed of the WC particles and the compound particles, the cemented carbide is excellent in wear resistance. As for content with respect to the cemented carbide of the metal contained in a compound particle, 0.05 mass%-5 mass% are preferable. This is to ensure the wear resistance and heat crack resistance of the cemented carbide.

  The WC particles are substantially composed of fine particles having an average particle diameter of 0.4 μm to 0.6 μm measured by the Fisher method and coarse particles having an average particle diameter of 1.2 μm to 1.4 μm measured by the Fisher method. Configured. The Fischer method is a particle size test method defined in TMIAS 0001: 1999, and is a method (permeation method) in which air is passed through a sample to obtain a specific surface area from measurement of flow velocity and pressure drop, and an average particle diameter is calculated. . The ratio of fine particles and coarse particles is such that the mass ratio is fine particles / coarse particles = 25/75 to 15/85. Thereby, fine WC particles enter the gaps between the coarse WC particles, and the WC particles can be densely arranged. As a result, the toughness, strength and hardness of the cemented carbide can be secured, and the adhesion of the coating can be secured.

  The binder phase is for binding the hard phase and is mainly composed of Co. The binder phase can contain other iron group elements such as Ni and Fe in addition to Co. The content of Co is preferably 0.7% by mass to 2% by mass with respect to the cemented carbide. This is to ensure the toughness and hardness of the cemented carbide. If the Co content relative to the cemented carbide is less than 0.7% by mass, the toughness of the cemented carbide tends to decrease. When the content of Co in the cemented carbide exceeds 2% by mass, the amount of Co on the surface of the base material increases. Therefore, when attempting to coat the base material by vapor phase synthesis of diamond, graphite is likely to be generated. When the substrate is pickled to prevent this, the amount of Co removed from the surface of the substrate increases, so the surface of the substrate tends to become brittle and the adhesion of the coating decreases.

  Examples of the element include one or more selected from Cr, Nb, Zr, V, and Ti. When the content of the element with respect to the cemented carbide is 0.09% by mass to 0.9% by mass, the growth of the WC particles constituting the hard phase can be suppressed, so that the size and shape of the starting material can be easily maintained. . Therefore, the state where the fine WC particles enter the gaps between the coarse WC particles is maintained, and the WC particles can be densely arranged. As a result, the toughness, strength and hardness of the cemented carbide can be secured, and the adhesion of the coating can be secured. Since the WC particles are densely arranged, the WC particles can be bound by Co having a content of 0.7% by mass to 2% by mass with respect to the cemented carbide. When the content of the element with respect to the cemented carbide is less than 0.09% by mass, the above-described effect tends to be hardly obtained. When the content of the element with respect to the cemented carbide exceeds 0.9% by mass, the thermal diffusivity tends to decrease, and the thermal crack resistance and the wear resistance at high temperature decrease.

  In addition to one or more elements selected from Cr, Nb, Zr, V and Ti, the cemented carbide preferably contains Ta. This is because Ta can improve the effect of suppressing grain growth and improve oxidation resistance. The content of Ta is preferably 0.09% by mass to 0.9% by mass with respect to the cemented carbide. When the content of Ta with respect to the cemented carbide is less than 0.09% by mass, the above-described effect tends to be hardly obtained. When the content of Ta in the cemented carbide exceeds 0.9% by mass, the thermal diffusivity tends to decrease, and the thermal crack resistance and the wear resistance at high temperatures decrease.

In order to make one or more elements selected from Cr, Nb, Zr, V and Ti or Ta exist in the cemented carbide, a simple substance of the above metal element is mixed in the raw material, or the above metal element is contained. For example, a compound such as carbide (for example, Cr ₃ C ₂ , TaC, NbC, TaNbC, VC, ZrC, TiC, etc.) may be used. The compound used as the raw material exists as a compound in the superalloy as it is, forms a new composite compound, or exists as a single element.

  Cemented carbide is generally produced by a process of crushing and mixing raw materials, forming, and sintering. The raw materials are pulverized and mixed by various apparatuses such as a ball mill, an attritor, a Henschel mixer, and a jet mill. When the raw material is pulverized and mixed in a wet process, it is formed into the shape of a substrate after drying. Drying, molding and sintering are performed under known general conditions. Sintering is performed by hold | maintaining at 1320-1500 degreeC in a vacuum atmosphere for 1 to 2 hours, for example.

  The method for forming a diamond film on the surface of the substrate made of cemented carbide is not particularly limited. For example, a conventionally known method such as a plasma CVD method, a hot filament CVD method, or a plasma torch CVD method can be used.

  In addition, in order to improve the adhesiveness of the base material which consists of a cemented carbide, and a film, it is naturally possible to perform the pretreatment which pickles a base material before forming a film. According to the cemented carbide according to the present embodiment, the amount of Co present on the surface of the substrate can be reduced, so that the amount of Co removed when the substrate is pickled can be reduced. As a result, the surface of the substrate is less likely to become brittle, and thus the adhesion of the coating can be ensured.

  According to the above embodiment, a coating film is formed on the surface of the base material without forming an intermediate layer between the base material and the coating film. It is possible to eliminate the problem caused by the difference. Therefore, the reliability of the coating member in which the film is formed on the substrate can be improved. Moreover, since the process which forms an intermediate | middle layer is not required, the process and time for forming an intermediate | middle layer can be made unnecessary, and the coating process by a diamond film can be simplified.

  The present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In this example, the result of forming a diamond film on a substrate made of various cemented carbides and evaluating the adhesion of the film will be described. Table 1 shows the average particle diameters of fine particles and coarse particles of WC particles, the mass ratio of fine particles and coarse particles, the composition of cemented carbides manufactured with different contents of Co and elements, and the cemented carbides. It is a table | surface of the adhesiveness (durability time) of the diamond film formed in the base material which becomes. The average particle diameter of WC particles is a value measured by the Fisher method. In Table 1, the numerical value marked with * indicates that it is out of the numerical range of the present invention.

まず、ＷＣ粒子、Ｃｏ粒子、Ｃｒ_３Ｃ_２粒子、ＶＣ粒子、ＴａＣ粒子をそれぞれ準備し、表１に示す組成（質量％）になるように配合した。配合した粒子を混合後、押出成形し真空雰囲気で焼結して、実施例１〜８、比較例１〜１７の超硬合金からなる基材を得た。次に、ヘキサシアノ鉄（ＩＩＩ）酸カリウム１０ｇ及び水酸化カリウム１０ｇを１００ｍＬの蒸留水に溶かした腐食液（村上試薬）に基材を浸漬し、基材の表面を粗化した（表面の算術平均粗さＲａ約０．１μｍ）。次いで、マイクロ波プラズマＣＶＤ装置の反応容器内に基材を収容し、ダイヤモンド成膜用の原料ガスを反応容器内に供給して、基材の表面にダイヤモンド被膜（平均膜厚１０μｍ）を形成した。これにより実施例１〜８、比較例１〜１７の試料を得た。実施例１〜８、比較例１〜１７の試料は、組成が異なる以外、同一の条件で製造されている。

First, WC particles, Co particles, Cr ₃ C ₂ particles, VC particles, and TaC particles were prepared and blended so as to have the composition (mass%) shown in Table 1. After mixing the compounded particles, extrusion molding was performed and sintering was performed in a vacuum atmosphere to obtain a base material made of a cemented carbide of Examples 1 to 8 and Comparative Examples 1 to 17. Next, the base material was immersed in a corrosive solution (Murakami reagent) in which 10 g of potassium hexacyanoferrate (III) and 10 g of potassium hydroxide were dissolved in 100 mL of distilled water to roughen the surface of the base material (the arithmetic average of the surface) (Roughness Ra is about 0.1 μm). Next, the base material was accommodated in a reaction vessel of a microwave plasma CVD apparatus, and a raw material gas for forming a diamond film was supplied into the reaction vessel to form a diamond film (average film thickness 10 μm) on the surface of the base material. . This obtained the sample of Examples 1-8 and Comparative Examples 1-17. The samples of Examples 1 to 8 and Comparative Examples 1 to 17 are manufactured under the same conditions except that the compositions are different.

  Evaluation of the adhesion of the diamond coating was performed using a sandblasting apparatus. Using a sand blasting apparatus, silicon carbide (# 180) was projected at a discharge pressure (gauge pressure) of 300 kPa onto a 10 μm thick coating film, and the time until the coating film was peeled off from the substrate (endurance time) was measured. As shown in Table 1, the samples of Comparative Examples 1 to 17 had a durability time of up to 40 seconds, whereas the samples of Examples 1 to 8 had a durability time of 3 times or more (120 seconds or more). there were.

  According to this example, fine particles (WC particles) having an average particle size of 0.4 μm to 0.6 μm and coarse particles (WC particles) having an average particle size of 1.2 μm to 1.4 μm are fine particles / coarse particles. = 25/75 to 15/85 (mass ratio), Co content of 0.7 mass% to 2 mass%, element (Cr, V) content of 0.09 mass% to 0.9 mass% As a result, it was found that the adhesion of the film can be improved by 3 times or more as compared with the comparative example. Furthermore, it has been found that the durability time can be secured even when 0.09% by mass to 0.9% by mass of element (Ta) is added. According to the examples, it is possible to eliminate the process (conventional technology) of converting Co existing on the surface of the base material into silicide, thereby simplifying the process of forming the film and improving the adhesion of the film. It was.

In this embodiment, the case where Cr ₃ C ₂ particles, VC particles, and TaC particles (element carbide) are blended has been described. However, the present invention is not limited to this. Results were obtained. Further, the elements are not limited to Cr and V, and similar results were obtained even when Nb, Zr, and Ti having an effect of suppressing grain growth were blended.

  The present invention has been described above based on the embodiments. However, the present invention is not limited to the above embodiments, and various improvements and modifications can be made without departing from the spirit of the present invention. It can be easily guessed. For example, in cemented carbide, it is naturally possible to add compound particles other than WC particles to the hard phase, or to add metal materials other than Co and other additives to the binder phase.

Claims (2)

A hard phase mainly composed of WC particles;
A binder phase mainly composed of Co that binds the hard phase;
Containing one or more elements selected from Cr, Nb, Zr, V and Ti,
The WC particles are substantially composed of fine particles having an average particle diameter of 0.4 μm to 0.6 μm measured by the Fisher method and coarse particles having an average particle diameter of 1.2 μm to 1.4 μm measured by the Fisher method. Structured,
The fine particles and the coarse particles have a mass ratio of the fine particles / the coarse particles = 25/75 to 15/85,
The Co has a content of 0.7 mass% to 1.7 mass%,
The element, Ri content of 0.09 mass% to 0.9% by mass,
A cemented carbide characterized by not containing Ta . A hard phase mainly composed of WC particles;
A binder phase mainly composed of Co that binds the hard phase;
Containing one or more elements selected from Cr, Nb, Zr, V and Ti,
The WC particles are substantially composed of fine particles having an average particle diameter of 0.4 μm to 0.6 μm measured by the Fisher method and coarse particles having an average particle diameter of 1.2 μm to 1.4 μm measured by the Fisher method. Structured,
The fine particles and the coarse particles have a mass ratio of the fine particles / the coarse particles = 25/75 to 15/85,
The Co has a content of 0.7% by mass to 2% by mass,
The element, Ri content of 0.09 mass% to 0.9% by mass,
A cemented carbide containing 0.09% by mass to 0.9% by mass of Ta .