(2) The softening of work material becomes significant as cutting speed is increased. This, in turn, causes cutting forces to reduce. Abrasion is not important any more. The diffusion and oxidation would be more pronounced due to higher cutting temperature. A layer with oxidized compounds exhibiting a lower melting point is generated. This layer can protect cutting tool from wear. Hence, tool wear is reduced and tool life is prolonged.
(3) When there is very high cutting temperature, the sticking layer is worn away due to a great friction force. In addition, the bond between the CBN particles of the cutting tool is weakened owing to severe diffusion of work and tool mate- rials. Hence, CBN particles are plucked out of the tool face. Subsequently, cutting edge is weakened, and flank wear is increased.