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1. (WO2015113866) ALUMINA COATED CUTTING TOOL WITH ZIGZAG ALUMINA GRAIN BOUNDARIES

Pub. No.:    WO/2015/113866    International Application No.:    PCT/EP2015/050982
Publication Date: Fri Aug 07 01:59:59 CEST 2015 International Filing Date: Wed Jan 21 00:59:59 CET 2015
IPC: C23C 16/40
C23C 16/455
Applicants: WALTER AG
Inventors: RUPPI, Sakari
STIENS, Dirk
Title: ALUMINA COATED CUTTING TOOL WITH ZIGZAG ALUMINA GRAIN BOUNDARIES
Abstract:
A coated cutting tool insert consisting of a substrate of cemented carbide, cermet, ceramics, steel or cubic boron nitride having deposited thereon a coating of a total thickness of a maximum of 60 μm consisting of one or more refractory layers comprising an outer wear resistant layer of α-AI2O3 of a thickness of 2 to 45 μm deposited by chemical vapour deposition (CVD), wherein when observed in a SEM microphotograph of a cross section of the α-AI2O3 layer, the α-AI2O3 layer has an essentially columnar 01-AI2O3 grain structure, and the grain boundaries of at least 1 out of 25 01-AI2O3 grains, preferably at least 5 out of 25 α-AI2O3 grains, more preferably at least 15 out of 25 α-AI2O3 grains, along the length of the grain boundaries, undergo at least 3, preferably at least 4, more preferably at least 5, directional changes, wherein each directional change of two neighbouring sections of the same grain boundary is at an angle of from 15 to 165 degrees, preferably from 30 to 150 degrees, more preferably from 45 to 135 degrees.