Cemented carbide, cutting tool including same, and method of producing cemented carbide

Patent metadata

Field	Value
Publication number	US-11111564-B2
Application number	US-201916768214-A
Country	US
Kind code	B2
Filing date	Aug 8, 2019
Priority date	Oct 4, 2018
Publication date	Sep 7, 2021
Grant date	Sep 7, 2021

Abstract

A cemented carbide includes second hard phase grains, wherein the second hard phase grains includes a core portion, and in a case where a total of 70 unit regions that are each constituted of a square having each side of 8μm are provided by successively arranging 7 unit regions in a longitudinal direction and 10 unit regions in a lateral direction in an electron microscope image of any cross section of the cemented carbide captured at a magnification of 1500×, where the total number of core portions in the total of 70 unit regions is calculated, and where a percentage of the number of core portions in each of the unit regions with respect to the total number of core portions is calculated, the number of unit regions in which the percentage is less than 0.43% or more than 2.43% is less than or equal to 10.

First claim

The invention claimed is:

1. A cemented carbide comprising: first hard phase grains each including WC; second hard phase grains each including a carbonitride containing Ti and Nb; and a metal binder phase including an iron group element, wherein
each of the second hard phase grains includes a core portion in a form of a grain and a peripheral portion that coats at least a portion of the core portion,
the core portion is composed of a composite carbonitride represented by Ti 1-X-Z Nb X M Z C 1-Y N Y ,
the M is at least one impurity element selected from a group consisting of V, Cr, and Mo,
the X is more than or equal to 0.1 and less than or equal to 0.2,
the Y is more than or equal to 0.3 and less than or equal to 0.6,
the Z is more than or equal to 0 and less than or equal to 0.02,
the peripheral portion has a composition different from a composition of the core portion, and
a number of unit regions in which a percentage of the number of core portions in each of the unit regions with respect to the total number of core portions is less than 0.43% or more than 2.43% is less than or equal to 10, where
the cemented carbide has a total of 70 unit regions,
the total of 70 unit regions that are each constituted of a square having each side of 8 μm are provided by successively arranging 7 unit regions in a longitudinal direction and 10 unit regions in a lateral direction in an electron microscope image of any cross section of the cemented carbide captured at a magnification of 1500×, and
the total number of core portions in the total of 70 unit regions is calculated by counting the number of core portions in each of the unit regions.

2. The cemented carbide according to claim 1 , wherein each of the core portions the number of which is counted in each of the unit regions has a grain size of more than or equal to 0.2 μm and less than or equal to 3 μm.

3. The cemented carbide according to claim 1 , wherein the peripheral portion is a carbonitride containing Ti, Nb, and W.

4. The cemented carbide according to claim 1 , wherein an integrated value of 50% in an area-based distribution of grain sizes of the core portions is more than or equal to 0.2 μm and less than or equal to 2 μm.

5. The cemented carbide according to claim 1 , wherein a volume ratio of the core portions in the cemented carbide is more than or equal to 2 volume % and less than or equal to 10 volume %.

6. A cutting tool comprising the cemented carbide recited in claim 1 .

7. The cutting tool according to claim 6 , comprising: a substrate composed of the cemented carbide; and a coating film that coats the substrate.

8. A method of producing a cemented carbide, the method comprising:
obtaining a powder of a composite carbonitride represented by Ti 1-X-Z Nb X M Z C 1-Y N Y ;
obtaining a powder mixture by using a ball mill to mix the powder of the composite carbonitride, a WC powder, and an iron group element powder for more than or equal to 9 hours and less than or equal to 15 hours;
obtaining a molded body by performing pressure molding to the powder mixture; and
obtaining a sintered material by sintering the molded body, wherein
the M is at least one impurity element selected from a group consisting of V, Cr, and Mo,
the X is more than or equal to 0.1 and less than or equal to 0.2,
the Y is more than or equal to 0.3 and less than or equal to 0.6,
the Z is more than or equal to 0 and less than or equal to 0.02, and
the obtaining of the powder of the composite carbonitride includes
obtaining a third powder by mixing a first powder including Ti and Nb and a second powder at least including graphite,
obtaining a granulated body by granulating the third powder,
obtaining a powder precursor composed of the composite carbonitride by thermally treating the granulated body at more than or equal to 1800° C. under an atmosphere including nitrogen gas, and
obtaining the powder of the composite carbonitride by pulverizing the powder precursor.

Assignees

• Sumitomo Electric Hardmetal Corp

Inventors

• FUKAE Kosuke
• Kido Yasuki
• Watanabe Masami
• Imamura Shinya

Classifications

• C22C1/051 Primary

  Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor · CPC title

• C22C29/08 Primary

  based on tungsten carbide · CPC title

• C22C29/04

  based on carbonitrides · CPC title

• B22F1/142

  Thermal or thermo-mechanical treatment · CPC title

• B22F2999/00

  Aspects linked to processes or compositions used in powder metallurgy · CPC title