Abstract: 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.

Abstract: 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.

Abstract: An improved process for the production of coated cemented carbide products is disclosed. A cemented carbide substrate is treated to form a metal carbide, nitride or carbonitride coating. The coated substrate is heat treated at a temperature close to or near the melting point of the binder metal of the cemented carbide to diffuse elements from the substrate into the coating. An intermediate (second) metal carbide, nitride or carbonitride coating is thereafter applied and the portion of the second is oxidized, nitrided or sulfided without detrimentally affecting the adherence of the second coating. Thereafter, a wear-resistant oxide (e.g., aluminum oxide) coating is applied to form the improved coated carbide product.

Abstract: An improved process for the production of coated cemented carbide products is disclosed. A cemented carbide substrate is treated to form a metal carbide, nitride or carbonitride coating. During the last part of this treatment or subsequent thereto, a sulfur-and/or nitrogen-containing gas is added to the atmosphere to form a sulfide-and/or nitride - containing layer on the coating. Thereafter, a wear-resistant oxide (e.g., aluminum oxide) coating is applied to form the improved coated cemented carbide product.