Nickel-based alloy refers to the 650 ~ 1000 ℃ high temperature with high strength and certain oxidation corrosion resistance and so on comprehensive performance of the alloy. According to the main properties, it is divided into nickel base heat resistant alloy, nickel base corrosion resistant alloy, nickel base wear resistant alloy, nickel base precision alloy and nickel base shape memory alloy. According to the different matrix, the superalloy is divided into: iron base superalloy, nickel base superalloy and cobalt base superalloy. Nickel base superalloy is short for nickel base alloy.

Oxygen, nitrogen, carbon and hydrogen are the main impurities of titanium alloy. The solubility of oxygen and nitrogen in the phase was higher, and the plasticity decreased. It is generally stipulated that the content of oxygen and nitrogen in titanium is 0.15 ~ 0.2% and 0.04 ~ 0.05% respectively. The solubility of hydrogen in the first phase is very small, too much hydrogen dissolved in titanium alloy will produce hydride, which makes the alloy brittle. Generally, hydrogen content in titanium alloy is controlled below 0.015%. The solution of hydrogen in titanium is reversible and can be removed by vacuum annealing.