BeginnerTopic 32 of 100Materials & Chemical
Oxidation and high temperature degradation
Scale formation and creep limit service temperature.
In depth
At high temperature metals react with oxygen to form scales. Protective oxides (Al₂O₃, Cr₂O₃) grow slowly (parabolic kinetics) while porous ones spall. Pilling-Bedworth ratio indicates protectiveness. Sulphidation, carburisation and hot corrosion add complexity; coatings and alloying help.
Key points
- Parabolic rate law
- Scale adhesion
- Thermal cycling
ExampleFurnace alloys include chromium and aluminium to form protective scales.
What is Oxidation and high temperature degradation?
Scale formation and creep limit service temperature.
Why is it important to understand oxidation and high temperature degradation?
High-temperature oxidation and creep set the upper service limit for many components, such as boiler tubes and turbine parts.
What is oxide scale?
A layer of oxide formed on metal at high temperature, which may protect the surface if it is dense and adherent or may flake off.
Why does creep matter at high temperature?
Slow deformation under sustained load can lead to rupture long after the stress is applied, so creep life must be designed for.
How is Oxidation and high temperature degradation used in practice?
Typical applications include specifying a stainless steel for an exhaust system at high temperature, choosing an alloy for a furnace component that will oxidise slowly and estimating the life of a boiler tube before it creeps and ruptures.
What should I learn before Oxidation and high temperature degradation?
Study "Corrosion prevention" first (topic 31 of 100 in Materials & Chemical). It covers the groundwork this topic builds on.
What are the key points of Oxidation and high temperature degradation?
Parabolic rate law. Scale adhesion. Thermal cycling.
Can you give an example of Oxidation and high temperature degradation?
Furnace alloys include chromium and aluminium to form protective scales.
What comes after Oxidation and high temperature degradation?
The next topic is "Wear and tribology", which builds directly on this one.
How difficult is Oxidation and high temperature degradation?
It is classed as Beginner in Materials & Chemical (topic 32 of 100). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.