Heat resisting steel
In order to use steel in high temperature, it has to maintain intensity in high temperature and should not cause oxidation in the use condition, such as air and gas of high temperature. Oxidation resistance is effective when combined with aluminum, silicon, and chrome. Since aluminum and silicon are difficult to process, chromium steel is made added with chrome only followed by ally steel with chrome and molybdenum addition. And then sufficient chrome and nickel are added to obtain austenite (face-centered cubic structure) that is stabilized for high temperature. Today, chrome-molybdenum steel, 13 % chrome steel, 18-8 stainless steel are used for below or above 600 ℃, and high chrome steel (28 %), high nickel steel, and high chrome steel (20∼25 %) for up to 900 ℃. Heat-resisting steel is used for high-temperature tubes, high-temperature industrial equipment, and reactor parts.
Super heat resisting alloy
Super heat resisting alloy is a combination of superalloy, particle dispensed strengthened steel, and crystalline alloy, made to endure high temperature over 700℃, and is used as a turbine wing for jet engines. Superalloy consisting primarily of nickel or cobalt requires durability for corrosion, such as oxidation and emulsification or changes over time in dimension besides high temperature and intensity, thus promotes property optimization by adding alloying elements. Particle dispensed strengthened steel is mainly consists of TD nickel that dispersed dioxide-trium particles to nickel-base alloy, the super heat resisting alloy, and nickel-based superalloy that dispersed dioxide-trium of particulate. These alloys enhance super heat resisting alloy to endure the creep strain at high temperature.
Ni-based alloy is mostly heat-resistant materials, and different types of alloying elements are used for the base Ni, such as Cr (10-20), Co, Mo, Ti, Al. Heat-resistant Nickel-based alloy is generally called "Superalloy". The thermal resistance of the alloy requires a unique temperature dependency in gamma prime called Ni3Al according to Al addition. Cr is added to Nickel-based superalloy to enhance corrosion resistance at high-temperature; eventually, high-temperature creep property, high-temperature corrosion resistance, and high-temperature fatigue property are superior to general materials for the mechanical property of the Nimonic alloy.
The information herein is based on the Nimonic alloy types and property of "Heat-Resistant Materials" (ISBN: 0-87170-596-6) of the "ASM Specialty Handbook" published by ASM in the U.S.