| 摘要 |
The present invention introduces a new and refined method to produce alpha-Al<SUB>2</SUB>O<SUB>3 </SUB>layers with substantially better wear resistance and toughness than the prior art. The alpha-Al<SUB>2</SUB>O<SUB>3 </SUB>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 alpha-Al<SUB>2</SUB>O<SUB>3 </SUB>is obtained through a nucleation step being composed of both aluminising and oxidisation steps. The alpha-Al<SUB>2</SUB>O<SUB>3 </SUB>layer according to this invention has a thickness ranging from 1 to 20 mum and is composed of columnar grains. The length/width ratio of the alumina grains is from 2 to 12, preferably 5 to 9. The layer is characterised by a strong (012) growth texture, measured using XRD, and by the almost total absence (104), (110), (113) and (116) diffraction peaks.
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