Patent attributes
A new and refined method to produce α-Al2O3 layers in a temperature range of from about 750 to about 1000° C. with a controlled growth texture and substantially enhanced wear resistance and toughness than the prior art is disclosed. The α-Al2O3 layer of the present invention is formed on a bonding layer of (Ti,Al)(C,O,N) with increasing aluminium content towards the outer surface. Nucleation of α-Al2O3 is obtained through a nucleation step being composed of short pulses and purges consisting of Ti/Al-containing pulses and oxidising pulses. The α-Al2O3 layer according to the present invention has a thickness ranging from about 1 to about 20 μm and is composed of columnar grains. The length/width ratio of the alumina grains is from about 2 to about 12, preferably from about 4 to about 8. The layer is characterized by a strong (104) growth texture, measured using XRD, and by low intensity of (012), (110), (113), (024) and (116) diffraction peaks.
