There are quenched and tempered steel, hardened steel, carburized and quenched steel and nitriding steel gear used steel. Steel strength slightly lower than the forged steel, commonly used in the larger size of the gear; the poor mechanical properties of gray cast iron, can be used for the open gear transmission light load; nodular cast iron can partially replace steel gear; plastic gear for low noise local load and light, and the paired gears are commonly used steel gear with good thermal conductivity.

Future gears forward heavy, high precision and high efficiency, high speed, direction, and small size, light weight, long life and reliable. The development of gear theory and manufacturing process will be further study on Mechanism of tooth injury, this calculation method is to establish a reliable strength basis, is to improve the bearing capacity of the gear, theoretical basis for prolonging the service life of the gears; the development of new gear with circular arc tooth profile as the representative of the new technology of new type; gear materials and manufacturing gear the;

Study on the gear elastic deformation, the errors of manufacture and installation as well as the distribution of temperature field, of gear modification, to improve the stationarity of running gear, the contact area and increase the teeth under full load, so as to improve the bearing capacity of gear.

Friction, lubrication theory and lubrication technology is the basis of gear research work, research on the theory of elastohydrodynamic lubrication, promotion of the use of synthetic lubricating oil and the oil of properly adding the extreme pressure additives, not only can improve the load carrying capacity of gear surface, but also can improve the efficiency of transmission.