High Temperature Resistant Alloy
In high temperature environment, material face more complex and harsh condition. For example, some high-hardness materials are normal for service below 300 degrees, but hardness drops sharply when the temperature continue to increase.
Failure Under High Temperature Conditions
Turbine blades are exposed to the exhaust gas after combustion for a long period of time at a high temperature of more than 700 degrees. At the same time, the blades must withstand the pulling force generated by their rapid rotation. The combination of continuous force and high temperature creat a harsh condition.Nickel-based alloys have good high temperature creep resistance, they are often used to make turbine blades.
Cr and oxygen form a stable and dense oxide to protect the material from further corrosion. It can also be combined with Al/Si/Ce to play an antioxidant role.
When the component needs to withstand the cyclic heating and cooling, it is easy to crack and eventually lead to brittle fracture. For example, the exhaust pipe of a turbocharged engine. It is often necessary to quickly rise from normal temperature to 900 degrees high temperature, at the same time, it must withstand frequent vibrations. Glass molds and heat Forging dies, hot rolls, etc. need to face such condition too.
The mixed gas after fuel combustion contains various chemical components, such as Na2SO4, NaCl, etc. These salts will be deposited on the metal oxide surface. The original protective oxide film will be damaged. This will cause corrosion of the base metal.