M42 tool steel, a type of molybdenum high speed tool steel,which add  additional 8% -10% cobalt.It has  good wear resistance,hot hardness,high hardness capability (can be hardened to 68-70HRC)and  good machinability.These properties make the steel widely used in metal manufacturing industries,such as machining high-strength and pre-hardened steels, high-hardness alloys, and the difficult-to-machine, nonferrous super alloys used in the aerospace, oil, and power generation industries.