Method for depositing fine-grained alumina coatings on cutting tools

US6139921A · kind A · utility

Assignee

• SANDVIK AB · SE

Inventors

• Christine Taschner · Dresden, DE
• Ingolf Endler · Coswig, DE
• Albrecht Leonhardt · Dresden, DE
• Bjorn Ljungberg · Stuvsta-Snättringe, SE
• Mats Sjostrand · Sollentuna, SE

Key dates

• Filing date: Nov 23, 1998
• Grant date: Oct 31, 2000
• Expiry date: Nov 23, 2018

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C23C16/403
• WIPO field: Surface technology, coating
• WIPO sector: Chemistry

Abstract

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.