Cemented carbide and cutting tool
Provided are a cemented carbide having excellent plastic deformation resistance and a cutting tool in which the cemented carbide is used as a substrate. A cemented carbide includes a hard phase containing tungsten carbide particles and a binder phase containing, as a main component, an iron-group element, wherein the formula B/A≤0.05 is satisfied, where A represents the number of the tungsten carbide particles, and B represents the number of tungsten carbide particles whose number of contact points with other tungsten carbide particles is 1 or less. Preferably, the iron-group element includes cobalt, and the cobalt content in the cemented carbide is 8% by mass or more. Preferably, the tungsten carbide particles have an average particle diameter of 3 μm or more.
1. A cemented carbide comprising a hard phase containing tungsten carbide particles and a binder phase containing, as a main component, an iron-group element,
wherein the formula B/A≤0.05 is satisfied, where A represents the number of the tungsten carbide particles, and B represents the number of tungsten carbide particles whose number of contact points with other tungsten carbide particles is 1 or less,
wherein measuring the number of contact points of the tungsten carbide particles is configured to use an observation image that is obtained by a metallographic microscope or a scanning electron microscope,
wherein each of the contact points is a portion where the tungsten carbide particles are in contact with each other without the binder phase therebetween in a planar structure of the cemented carbide,
wherein the number of contact points is counted as 1 regardless of the size of thereof, in case that one of the tungsten carbide particles is continuously in contact with an adjacent tungsten carbide particle, and
wherein the number of contact points is configured to be measured by each of the tungsten carbide particles.
2. The cemented carbide according to claim 1 , wherein the cemented carbide includes, as the hard phase, a composite compound phase composed of at least one composite compound selected from carbides, nitrides, and carbonitrides containing Wand one or more elements selected from Group 4, 5, and 6 elements of the periodic table, excluding W, and Si;
the area fraction of the composite compound phase relative to any surface or cross section of the cemented carbide is 1% to 10%; and
the proportion of a composite compound phase portion having an area of 10 μm 2 or more is less than 5% in the entire composite compound phase present in the surface or cross section.
3. The cemented carbide according to claim 1 , wherein the iron-group element includes cobalt, and the cobalt content is 8% by mass or more.
4. The cemented carbide according to claim 1 , wherein the tungsten carbide particles have an average particle diameter of 3 μm or more.
5. A cutting tool in which the cemented carbide according to claim 1 is used as a substrate.
6. The cutting tool according to claim 5 , wherein the cutting tool is provided with a hard coating which covers at least part of a surface of the substrate.