Bromsgrove-based Walter GB Ltd (www.walter-tools.com) has developed a new titanium-aluminium-nitride (TiAIN) coating process that is said to improve carbide insert performance by offering tool-life increases of up to 200%.

Compared with inserts that are coated using the conventional chemical vapour deposition (CVD) process, Walter says that its new Tiger.tec Gold inserts offer higher resistance to wear on flank faces, reduced hairline cracking, greater resistance to plastic deformation and improved process reliability.

They are initially available in the WKP35G grade for milling steel and cast iron; other grades will follow.

By using TiAlN with an aluminium content of 85% — far higher than usual — in combination with a new ‘ultra-low-pressure’ CVD process, the company has been able to ‘separate’ TiAlN for use as the main gold-coloured coating, which is a good indicator of tool wear.

Titanium nitride (TiN) is used as a key between the carbide base substrate and the TiAlN coating — and as the top textured layer (above the main coating).

The benefits offered by Tiger.tec Gold WKP35G inserts have been confirmed by numerous tests at cutting speeds between 120 and 320m/min on various grades of steel and cast iron.

Walter says the increased performance achieved by applying the TiAlN coating using the low-pressure CVD procedure is
attributable to the residual stress in the insert/coating being compressive rather than tensile.