Epitaxial Growth Mechanism of a Bonding Layer and an α-Al_2O_3 Layer on a Ti(C,N)Layer

摘要

Microstructure of a newly developed "long-tool-life"α-Al_2O_3 coated cutting tool and mechanism of epitaxial growth of the α-Al_2O_3 layer has been investigated. The tool was produced by coating cemented carbide chips with layers of a TiN layer, a Ti(C, N) layer, a bonding layer and anα-Al_2O_3 layer successively and in this order using the techniques of CVD. Cross section TEM Analysis revealed the existence of a column in whichα-Al_2O_3 grains had grown epitaxially around a protrusion formed around a {111} twin plane in the bonding layer twin which had in turn had grown in a similar way (epitaxially) on a surface of a Ti(C,N) twin, and also the surface of the protrusion is civered with steps on the atomic scale.