Sandvik Ab

Jan N Lindstrom

Mats E Sjostrand

Ingrid K Collin

Christopher G Chatfield

Bjorn Ljungberg

Leif E Akesson

Asa K Nystrom

A sintered hard material body is at least partly coated with at least one 0.5-20 .mu.m wear resistant ceramic oxide coating being &lt;80% thicker in the edges than on the flat surfaces. The oxide coating exhibits a grain size (.O slashed.) in .mu.m for which:

Alumina-coated sintered body

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

A coated body consisting of a substrate that can be decarburized during a carbide, nitride or carbonitride coating process comprising a first (innermost) carbon diffusion retarding coating of MetCO, MetCON, MetON adjacent to the substrate and a second (next innermost) wear resistant coating of MetC, MetN and/or MetCN, where Met is Ti, Hf, V, Zr, Si, B or other metals of subgroup 3-7 of the periodic table of the elements, or a mixture thereof. The intermediate coating has been found beneficial in order to reduce or even eliminate the formation of eta phase in the substrate.

Diffusion barrier coating material

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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Hagersten, Sweden

Jan N Lindstrom