High-speed metal milling with a new cobalt-enriched high-speed steel grade

Metal cutting tools are usually made from high-speed steels using a conventional process (ingots) or powder metallurgy. But their poor behaviour at high temperatures limits their performance at very high speeds (> 250 m/s): premature wear, poor surface conditions.... Therefore, for dry cutting or very high speed milling (up to 350-400 m/s), the current solution is to use tools made from tungsten carbides or sometimes steels containing intermetallics (MC90) which have better resistance to higher temperatures. However, their uses are limited because of a much higher cost and a poor resilience. Moreover carbide tools do not allow sharp edges whereas high-speed steels do.

We have developed a new high-speed steel grade with a high cobalt content (up to 30% in weight) allowing higher performance cutting tools. Unlike intermetallics including 10% cobalt maximum, cobalt is not contained in precipitates but is distributed in a solid solution in the matrix of the steel. This new grade will allow to overcome the limits of current high-speed steels and to achieve the performance levels of intermetallics (wear, milling speed of > 300 m/s, sharp edges) without their drawbacks of poor resilience and complex manufacturing of both semi-finished products and cutting tools. The cost of this new grade is close to that of conventional high-speed steel (20-40 euros/kg) and thus much lower than the costs of carbides or intermetallics (80-100 euros/kg).