Sandvik Ab

Ingrid K Collin

Mats E Sjostrand

Jan N Lindstrom

Christopher G Chatfield

The present invention relates to a method for coating a cutting insert having at least one layer of a carbide, carbonitride, oxynitride, oxycarbide, oxycarbonitride or nitride of one metal selected form the groups IVB, VB or VIB of the Periodic Table, the method comprising subjecting the insert to chemical vapor deposition and coating the insert with an epitaxial kappa-Al.sub.2 O.sub.3 layer by the hydrolysis reaction of AlCl.sub.3, H.sub.2 and CO.sub.2, the hydrolysis reaction being carried out while maintaining the content of water vapor in the gas phase during nucleation of Al.sub.2 O.sub.3 at less than 5 ppm.

CVD of Al.sub.2 O.sub.3 layers on cutting inserts

The present invention relates to a body coated with at least one double layer Al.sub.2 O.sub.3 -TiC. Because the Al.sub.2 O.sub.3 -layer in contact with the TiC-layer consists of kappa-Al.sub.2 O.sub.3 or theta-Al.sub.2 O.sub.3 an improved adherence has been obtained. A further improvement of the properties is obtained if the body after the coating is heat treated for 0.3-10 hours at 900.degree.-1100.degree. C. in protecting gas atmosphere at which initially nucleated kappa- or theta-Al.sub.2 O.sub.3 is transformed to fine grained alpha-Al.sub.2 O.sub.3.

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Enskede, Sweden

Ingrid K Collin