Steel quality for underwater propeller axles 1

[magnusrm]

Hi.
Im making a electric thruster for underwater applications (sea water).
The propeller axle goes through a radial rubber seal from the internally oil filled casing.

Ive previously used super duplex / duplex steel (EN 1.4410 / ASTM UNS S32750, EN 1.4460 / AISI 329 or EN 1.4462). The 316 SS will be too soft over time, as particles at the radial seal will wear it down.

Do you have any other suggested steel qualities or input on the materials I mentioned? I would prefer to use a steel that is widely used (also in Europe) and hence has good availability.

thank you.

 

[EdStainless]

Frequently used is cold drawn Nitronic 50 bar (sold as aquamet 22).
Superduplex is fine option, But hard to find.
Also good but not very common would be cold finished 6%Mo superaustenitic.
So that leaves K-500 Ni-Cu, this alloy in the annealed and aged condition works very well as shafting.
I used a lot of K-500 as pump shafting, it works well.

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P.E. Metallurgy, Plymouth Tube

 

[magnusrm]

Thank you very much, Ed.

 

[Guest102023]

Ditto Ed's comment,

I have seen Nitronic 30 used for propellor shafts.
I would guess that alloys like K-500 with a high copper content could be more resistant to zebra mussel attachment, but you would need to investigate that.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[EdStainless]

Nit 30 won't stand up in seawater.
Monel 400 will work if you can use the lower strength, K-500 is the high strength version.
You will have hard time finding an alloy that does better in seawater.

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P.E. Metallurgy, Plymouth Tube