Indexable insert

An indexable insert (1) comprising a substrate (8) and a coating layer (11) formed on the substrate (8),

• wherein the substrate (8) has at least two flank faces (3), at least one rake face (2), and at least one corner (9),
• each flank face (3) and the rake face (2) are connected with an edge line (4) provided therebetween,
• the corner (9) is the point of intersection of the two flank faces (3) and the one rake face (2),
• the coating layer (11) includes an inner layer (12) including at least one layer and an outer layer (13) formed on the inner layer (12),
• the inner layer (12) includes an alumina layer or an alumna-containing layer serving as an outermost layer in contact with the outer layer (13),
• the outer layer (13) is composed of at least one metal selected from the group consisting of the periodic table group IVa elements, Va elements, and VIa elements, Al, and Si or a compound of at least one of the metals and at least one element selected from the group consisting of carbon, nitrogen, oxygen, and boron, and
• the outer layer (13) satisfies B/A≦0.9 wherein A μm is the average thickness in a segment region of 0.5 mm to 1 mm from the corner (9) to the flank face (3) side, and B μm is the average thickness in a segment region of 0.5 mm to 1 mm from the corner (9) to the rake face (2) side on a line passing through the corner (9) involved in cutting, dividing the angle formed by the two flank faces (3) constituting the corner (9) into two equal parts on the rake face (2), and extending from the rake face (2) to the intersectional line of the two flank faces (3).

An indexable insert (1) comprising a substrate (8) and a coating layer (11) formed on the substrate (8),

• wherein the substrate (8) has at least one flank face (3) and at least one rake face (2),
• the flank face (3) and the rake face (2) are connected with an edge line (4) provided therebetween,
• the coating layer (11) includes an inner layer (12) including at least one layer and an outer layer (13) formed on the inner layer (12),
• the inner layer (12) includes an alumina layer or an alumna-containing layer serving as an outermost layer in contact with the outer layer (13),
• the outer layer (13) is composed of at least one metal selected from the group consisting of the periodic table group IVa elements, Va elements, and VIa elements, Al, and Si or a compound of at least one of the metals and at least one element selected from the group consisting of carbon, nitrogen, oxygen, and boron,
• the inner layer (12) is exposed in a region extending with a distance of less than 0.4 mm from the edge line (4) to the flank face (3) side and a region extending with a distance of less than 2 mm from the edge line (4) to the rake face (2) side, the surface of the exposed portion of the inner layer (12) being composed of an alumina layer or an alumina-containing layer,
• the outer layer (13) satisfies B/A≦0.9 wherein A μm is the average thickness in a region extending with a width of 0.2 mm from a point at a distance of 0.4 mm from the exposed portion of the inner layer (12) to the center of the flank face (3), and B μm is the average thickness in a region extending with a width of 0.2 mm from a point at a distance of 0.4 mm from the exposed portion of the inner layer (12) to the center of the rake face (2).