Indexable insert

An indexable insert comprising a substrate and a coating layer formed on the substrate, wherein

• the substrate has at least two flank faces, at least one rake face, and at least one corner,
• the flank faces and the rake face are connected to one another with an edge line therebetween,
• the corner is the point of intersection of the two flank faces and the rake face,
• the coating layer includes an inner layer constituted by one or more layers and an outer layer formed on the inner layer,
• the innermost layer constituting the inner layer in contact with the substrate is composed of a compound containing at least one element selected from the group consisting of Group IVa elements, Group Va elements, and Group VIa elements in the periodic table, and Al and Si;
• and at least one element selected from the group consisting of carbon, nitrogen, oxygen, and boron, and the uppermost layer of the inner layer in contact with the outer layer is composed of a compound at least containing Ti and at least one of nitrogen and boron and excluding carbon, and the layer other than the innermost layer and the uppermost layer is composed of a compound containing at least one element selected from the group consisting of Group IVa elements, Group Va elements, and Group VIa elements in the periodic table, and Al and Si;
• and carbon or a combination of carbon and at least one element selected from the group consisting of nitrogen, oxygen, and boron,
• the outer layer is constituted by an alumina layer or an alumina-containing layer, and
• on a straight line that passes through the corner, bisects the angle formed on the rake face by the two flank faces constituting the corner, and extends from the rake face to an intersection line between the two flank faces, the outer layer satisfies B/A≦0.9, where the average thickness of a segment region 0.5 mm or more and 1 mm or less from the corner toward the flank face side is A μm and the average thickness of a segment region 0.5 mm or more and 1 mm or less from the corner toward the rake face side is B μm,
• wherein a compressive stress of the rake face is larger than the compressive stress of the flank face.