EP-4317502-B1 - POWDER MATERIAL FOR ADDITIVE MANUFACTURING AND METHOD FOR MANUFACTURING AN ADDITIVE-MANUFACTURED PRODUCT

Inventors

• YAMADA, JUNYA
• IBE, HIROYUKI
• KATO, Yuta

Dates

Publication Date

20260513

Application Date

20220323

Claims (4)

1. A powder material for additive manufacturing, comprising tungsten carbide (WC) in a content of 60% by mass or more of the entire powder material, cobalt (Co) in a content of 10% by mass or more of the entire powder material, and a carbon additive including carbon (C) as a main constituent element, wherein at least one solid carbon material selected from the group consisting of graphite, carbon black, activated carbon, carbon fiber and nanocarbon is included as the carbon additive, wherein the powder material is composed of granulated sintered particles in which the tungsten carbide, the cobalt, and the carbon additive are mixed, wherein the granulated sintered particles have an average particle size of 10 µm or more and 30 µm or less, particles consisting of the tungsten carbide and having an average particle size of less than 1 µm, particles consisting of the cobalt and having an average particle size of 2 µm or more and 10 µm or less, and particles constituting the carbon additive and having an average particle size of 1 µm or more and 5 µm or less, are included herein as particles constituting the granulated sintered particles, wherein the respective average particle size at 50% of the integrated value in the volume-based particle size distribution is measured as described in the description, and the strength of the granulated sintered particles is 5 kgf/mm 2 or more and 50 kgf/mm 2 or less, as measured by a method described in the description, and the value of a carbon content A (% by mass), which is represented by the following formula: [(mass of C derived from WC) + (mass of C derived from carbon additive)]/(mass of WC) × 100, satisfies the condition of 6.4 ≤ A ≤ 7.2.
2. The powder material according to claim 1, wherein the value of the carbon content A (% by mass) satisfies the condition of 6.6 ≤ A ≤ 6.9.
3. The powder material according to claim 1 or 2, comprising a carbide of at least one metal selected from the group consisting of titanium (Ti), vanadium (V), chromium (Cr), niobium (Nb) and molybdenum (Mo) as the carbon additive.
4. A method for manufacturing an additive-manufactured product, wherein additive manufacturing is performed using the powder material according to any one of claims 1 to 3, and wherein the ratio of the intensity of the peak (40.1°) indicating Co 3 W 3 C (η phase) and the intensity of the peak (35.6°) indicating WC is either 0%, less than 1%, or 1% or more and less than 3% measured by X-ray diffraction method on the obtained additive-manufactured product.

Description

Technical Field The present invention relates to a powder material suitable for additive manufacturing. The present invention also relates to a method for manufacturing an additive-manufactured product characterized by using the powder material and performing additive manufacturing. This application claims priority from Japanese Patent Application No. 2021-059464 filed on March 31, 2021. Background Art The so-called three-dimensional manufacturing techniques by which a additive-manufactured product, which is the object to be manufactured, is produced based on three-dimensional shape data thereof (for example, three-dimensional CAD data) are widely used. One of such manufacturing techniques is an additive manufacturing method by which a powder material is laid in thin layers and then bonded or sintered into a shape corresponding to the cross section of the additive-manufactured product, which is to be manufactured, and these thin layers are sequentially and integrally stacked. Conventionally, resin materials have been widely used as powder shaping materials used for such additive manufacturing, but in recent years, powder materials for additive manufacturing that are made of metals and ceramics that can be used for additive manufacturing by a powder bed fusion method (PBF), laser powder build-up method (LMD), etc. have been actively developed (see Patent Documents 1 to 4). As examples, Patent Documents 5 and 6 as well as Non-Patent Documents 1 to 3 relate to WC-Co based cemented carbide powders. Citation List Patent Document Patent Document 1: WO 2015/194678 A1Patent Document 2: Japanese Patent Application Publication No. 2017-113952Patent Document 3: Japanese Patent Application Publication No. 2017-114716Patent Document 4: Japanese Patent Application Publication No. 2017-115194Patent Document 5: Chinese Patent Application Publication No. 111 663 067Patent Document 6: Japanese Patent Application Publication No. 2020-020014 Non-Patent Document Non-Patent Document 1: Duman et al. "Synthesis, microstructure, and mechanical properties of WC-TiC-Co ceramic composites", J EUR CERAM SOC, 2012, Vol. 32, No. 7, 1427-1433Non-Patent Document 2: Zackrisson et al. "WC-Co based cemented carbides with large Cr3C2 additions", INT J REFRACT MET HARD MATER, 1998, Vol. 16, No. 4-6, 417-422Non-Patent Document 3: Boccarusso et al. "Effects of Cr3C2 Addition on Wear Behaviour of WC-Co Based Cemented Carbides", MET, 2018, Vol.8, No. 11, 895 Summary of Invention One of the development goals of powder materials for additive manufacturing that are made of inorganic materials such as metals and ceramics is the development of powder materials that can produce additive-manufactured products with high mechanical strength that are free from cracks and chips. As materials that meet this goal, powder materials including tungsten carbide (WC) and cobalt (Co) as main components have been actively developed. Tungsten carbide and cobalt are raw materials for cemented carbides (WC-Co alloys) and are suitable as materials for manufacturing additive-manufactured products with high hardness by additive manufacturing. However, regarding powder materials that include tungsten carbide and cobalt as main components and that have been heretofore developed, there is still room for improvement in terms of further increasing the mechanical strength of additive-manufactured products. In view of such circumstances, it is an object of the present invention to provide a powder material for additive manufacturing that includes, as main components, tungsten carbide and cobalt that can form an additive-manufactured product with more excellent mechanical strength (hereinafter can be also referred to as "WC/Co-containing powder material"). Another object of the present invention is to provide a method for manufacturing an additive-manufactured product, characterized by performing additive manufacturing using such a powder material. In order to achieve the above objects, the present inventors have conducted detailed investigation of the alloy structure of additive-manufactured products made of powder materials including tungsten carbide and cobalt as main components. As a result, it was found that where a η phase is present in the additive-manufactured product, the higher the presence ratio thereof, the lower the mechanical strength, and by intentionally increasing the content of carbon (C) contained in the WC/Co-containing powder material to be used for additive manufacturing, it is possible to suppress the formation of the η phase, which is a brittle phase, and increase the mechanical strength of the additive-manufactured product. This finding led to the completion of the present invention as set out in the appended set of claims. The powder material for additive manufacturing disclosed herein comprises tungsten carbide (WC), cobalt (Co), and a carbon additive including carbon (C) as a main constituent element. In the WC/Co-containing powder material, where the va