TECHNICAL FIELD

The present disclosure relates to cutting tools.

BACKGROUND ART

Cutting tools having a coating formed on a base material have been conventionally used. Aluminum oxide having an α-type crystal structure (hereinafter also referred to as “α-Al₂O₃”) has been used as a coating material, due to its excellent mechanical properties (see Japanese Patent Laying-Open No. 6-316758 (PTL 1) and Japanese Patent Laying-Open No. 2013-111720 (PTL 2)).

CITATION LIST
Patent Literature

PTL 1: Japanese Patent Laying-Open No. 6-316758

PTL 2: Japanese Patent Laying-Open No. 2013-111720

SUMMARY OF INVENTION

The cutting tool of the present disclosure is a cutting tool comprising a base material and a coating arranged on the base material; wherein:

the coating comprises an α-Al₂O₃layer;

the α-Al₂O₃layer is composed of a plurality of α-Al₂O₃particles;

the α-Al₂O₃layer comprises a first region, a second region and a third region;

the first region is a region sandwiched between an interface P1 on the base material side of the α-Al₂O₃layer and a virtual surface S1 that is located at a distance of 0.5 μm from interface P1 toward the surface side of the coating;

the second region is a region sandwiched between virtual surface S1 and a virtual surface S2 that is located at a distance of 1.0 μm from virtual surface S1 toward the surface side of the coating;

the third region is a region sandwiched between a surface P2 of the α-Al₂O₃layer or an interface P3 on the surface side of the coating of the α-Al₂O₃layer and a virtual surface S3 that is located at a distance of 1.0 μm from surface P2 or from interface P3 toward the base material side;

the average particle diameter a of the α-Al₂O₃particles in the first region is 0.10 μm or more and 0.30 μm or less;

the average particle diameter b of the α-Al₂O₃particles in the second region is 0.30 μm or more and 0.50 μm or less;

the average particle diameter c of the α-Al₂O₃particles in the third region is 0.10 μm or more and 0.30 μm or less; and

the ratio b/a between the average particle diameter b and the average particle diameter a is 1.5 or more and 5.0 or less.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing an example of a cross section of a cutting tool according to Embodiment 1.

FIG. 2 is a schematic diagram showing another example of a cross section of a cutting tool according to Embodiment 1.

FIG. 3 is a schematic diagram showing another example of a cross section of a cutting tool according to Embodiment 1.

FIG. 4 is a schematic diagram showing another example of a cross section of a cutting tool according to Embodiment 1.

FIG. 5 is a diagram schematically showing an example of a backscattered electron image of an α-Al₂O₃layer.

FIG. 6 is a diagram illustrating a method for measuring the average particle diameter of an α-Al₂O₃layer.

FIG. 7 is a diagram illustrating a method for measuring the average particle diameter of an α-Al₂O₃layer.

DESCRIPTION OF EMBODIMENTS
Technical Problem

An α-Al₂O₃layer is excellent in mechanical properties, but requires further improvement in adhesion to the other layers and in fracture resistance. In addition, high-hardness steel also requires further improvement in wear resistance.

Therefore, an object of the present disclosure is to provide a tool having a long tool life even in high-efficiency machining of high-hardness steel.

Advantageous Effects of Invention

The cutting tool of the present disclosure can have a long tool life even in high-efficiency machining of high-hardness steel.

Description of Embodiments

First, Embodiments of the present disclosure will be listed and illustrated.

(1) The cutting tool of the present disclosure is a cutting tool comprising a base material and a coating arranged on the base material; wherein: