ZIRCONIUM GETS FRIENDLY WITH INSERTS

Widia Valenite, the German cutting insert company owned by Cincinnati Milacron, has developed a coating technique that for the first time allows zirconium to be coated on carbide inserts. Zirconium has long been desired as an insert coating because of its ability to lengthen the life of the tool – the cutting edge on machinery […]

Widia Valenite, the German cutting insert company owned by Cincinnati Milacron, has developed a coating technique that for the first time allows zirconium to be coated on carbide inserts.

Zirconium has long been desired as an insert coating because of its ability to lengthen the life of the tool – the cutting edge on machinery – by 20%.

The metal is smoother than conventional titanium nitride coating and is more efficient in pulling away waste chip material. This makes it last longer.

Hard metal layers have conventionally been applied using physical vapour deposition (PVD) techniques. A method known as sputtering heats the metal to temperatures of around 500 degreesC and physically deposits atoms of zirconium on to the cutting tool.

PVD does not allow very thick layers, however, because it builds up stresses in the material. Chemical vapour deposition (CVD) is a much more promising prospect.

Engineers can build up a thick, stress free coating on cemented carbide by chemically reacting gases of coating materials together. The problem with zirconium is that it has to be heated to temperatures of around 2000 degreesC before it vaporises, making it very difficult to handle.

Widia has found a way round the problem by transforming zirconium into a gas-friendly compound, that it has patented, which forms a hard zirconium carbonitride layer on a cemented carbide insert when combined with carbon and nitrogen in a gas chamber.

The new coating has been developed for conventional steels and grey cast iron. The company is developing material for stainless steels.