In a gas turbine nozzle made of cobalt-based superalloy, the grain size is larger than normal.
What are the differences between this part in terms of mechanical properties with another part that has a normal grain size?
Especially stress corrosion cracking.
I think that according to the famous Hall-Petch law, based on the hardening of materials in relation to the size of the constituent grains,
having coarse grains is a disadvantage in that the material is less mechanically resistant,
On the other hand, the large specific surface of the grains, increases the probability of a corrosion attack and an easy propagation of the cracks.
So in my opinion, the turbine will be better with small grains.
Greetings!
Effect of grain size on stress corrosion cracks propagated inter-granularly regardless of grain size.
Dear Dr Bahare Ghasemi . See the following useful RG link: Article Effect of Grain Size on the Stress Corrosion Cracking of Ult...
Kindly see also the following useful RG link: Article Stress Corrosion Cracking Behavior of Fine-Grained Al5083 Al...
Also check please the following useful RG link: Chapter Stress Corrosion Cracking Behavior of Materials
The factor limiting gas turbine life is thermal fatigue. Forged components are naturally fine-grained, cast parts correspondingly coarse-grained. This is irrelevant for the service life.
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