Steels are divided into carbon steel and alloy steel. Carbon steel
offers low cost and can be hardened. A major disadvantage is the lack of
resistance to corrosion.Alloy steel is elements like stainless steel, and elements other than carbon. They offer high strength and a wide range of heat treatment properties. They provide highest strength and durability. Stainless steel may be stainless steel (austenitic) that is non-magnetic and has good corrosion resistance; they may be of stainless steel (martensitic) that can be easily hardened by heat, is magnetic and have reasonable corrosion resistance. Stainless steel (aust) can be used where low power ratings are there and the other stainless steel is used where low to medium power ratings is there. Alloy steels are used in industrial field.
While making gears many times few minerals are added to steel. These minerals are nickel, chromium, vanadium, manganese, molybdenum, and chrome-nickel.
Nickel - Increases hardness and strength.
Chromium - Increases hardness and strength but the loss of ductility is greater. It refines the grain and imparts a greater depth of hardness. It has high degree of wear resistance.
Manganese - It gives greater strength and a high degree of toughness than chromium.
Vanadium - The hardness penetration is greatest. The loss of ductility is also more than any other alloys.
Molybdenum - Increases strength without affecting the ductility.
Chrome - Nickel Steels - The combination of the two alloying elements chromium and nickel adds the beneficial qualities of both.