What steel is commonly used for gears and sprockets, and what heat treatment is needed?

The materials commonly used to manufacture sprockets and gears are gray cast iron, low carbon steel, medium carbon steel, low carbon alloy steel and medium carbon alloy steel. (HT20-40, HT25-47, HT30-54, 45# steel, 40Cr, 40MnB, 15, 20, 20Cr, 18CrMnTi, 35CrMo) The heat treatment of gears made of gray cast iron is stress relief annealing, and gears made of low carbon steel are carburized. In a word, different materials adopt different heat treatment methods to make gears and sprockets have high surface hardness, good wear resistance and good center toughness, thus achieving the purpose of good impact resistance.