Grain Boundary Engineered Alpha-Alumina Coated Cutting Tool

Abstract

Cutting tool insert has a substrate and a coating with a total thickness of 5 to 40 μm, the coating being one or more refractory layers of which at least one layer is an α-Al2O3 layer having thickness of 1 to 20 μm. The length of Σ3-type grain boundaries in the at least one α-Al2O3 layer is more than 80% of the total length of the sum of grain boundaries of Σ3, Σ7, Σ11, Σ17, Σ19, Σ21, Σ23 and Σ29-type grain boundaries grain boundary character distribution measured by EBSD. The at least one α-Al2O3 layer is deposited by chemical vapour deposition (CVD) using reaction gases comprising H2, CO2, AlCl3 and X and optional additions of N2 and Ar, with X being gaseous H2S, SO2, HF, SF6 or combinations thereof. The volume ratio of CO2 and X in the CVD reaction chamber lies within the range 2<CO2/X<10.

Dependencies are inferred from the claim text.