The main features of the laser as a heat source for transformation hardening are:(A) Clean energy source.(B) Energy is localised: no heat spillage.(C) Only surface layer heated: core properties are unaltered.(D) Low heat input: therefore low thermal distortion.(E) Fast process: therefore no oxidation. The process can be a final operation.(F) Self quenching: no water or oil sprays.(G) Easily automated: the laser fits naturally into a numerically controlled system with time sharing between work stations.