Patent attributes
The present invention relates to a method of depositing a crystalline α-Al2O3-layer onto a cutting tool insert by Chemical Vapor Deposition at a temperature of from about 625 to about 800° C. The method comprises the following steps:depositing a from about 0.1 to about 1.5 μm layer of TiCxNyOz where x+y+z>=1 and z>0, preferably z>0.2;treating said layer at 625-1000° C. in a gas mixture containing from about 0.5 to about 3 vol-% O2, preferably as CO2+H2 or O2+H2, for a short period of time from about 0.5 to about 4 min, optionally in the presence of from about 0.5 to about 6 vol-% HCl; anddepositing said Al2O3-layer by bringing said treated layer into contact with a gas mixture containing from about 2 to about 10 vol-% of AlCl3, from about 16 to about 40 vol-% of CO2, in H2 and 0.8-2 vol-% of a sulphur-containing agent, preferably H2S, at a process pressure of from about 40 to about 300 mbar. The invention also includes a cutting tool insert with a coating including at least one α-Al2O3-layer according to the invention.
