Sandvik Ab

Christine Taschner

Bjorn Ljungberg

Ingolf Endler

Mats E Sjostrand

Albrecht Leonhardt

A method for depositing refractory alumina (A.sub.2 O.sub.3) thin layers on cutting tools made of cemented carbide, cermet, ceramics or high speed steel is disclosed. The present method is a Plasma Activated Chemical Vapor Deposition (PACVD) process in which the plasma is produced by applying a bipolar pulsed DC voltage across two electrodes to which the tool substrates to be coated are fixtured and electrically connected. In contrast to prior art methods, built-up electrical charge on non-conducting surfaces is suppressed and hence, no arcing occurs on said surfaces. This will permit stable, long-term processing, With the present method, high-quality coatings of either single phase gamma-Al.sub.2 O.sub.3 or of a mixture of gamma- and alpha-Al.sub.2 O.sub.3 phases can be deposited on cutting tools at deposition temperatures as low as 500.degree. C. When coated cemented carbide tools according to the invention are used in the machining of steel or cast iron, several important improvements to prior art produced Al.sub.2 O.sub.3 -coated tools have been observed.

Growing community of inventors

Dresden, Germany

Christine Taschner