17-4PH SS Steel

[Erkamal]

Hi Dear all,
i have generally used 17-4 PH ss for valve stem for high strength and corrosion resistance for valve stem. But is it good for salty atmosphere?i have little doubt.
Which material good for above atmosphere?

 

[boo1]

We use 17-4 PH all the time in marine env.

 

[metengr]

What is a "salty environment"?? If you mean where chlorides can concentrate at elevated temperature or in an aqueous, marine environment? Not enough information. You have duplex stainless steel as a valve stem option again, depending on your salty environment.

 

[EdStainless]

17-4PH has worse pitting resistance than 304, and depending on the strength level is also is very susceptible to chloride stress corrosion cracking.
15-7PH would be a modest improvement in corrosion resistance.
But if you need that strength level (>175ksi) and good resistance to crevice corrosion and SCC you will need to look at an age hardening Ni alloy like 718.


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Plymouth Tube

 

[OGMetEngr]

EdStainless knows what he's talking about. Look at the Copson Curve and you'll see that 17-4, 15-7, and 304 (8%Cr) all have maximum susceptibility to chloride-induced stress corrosion cracking in salty wet environments. 17-4 pitting/crevice corrosion resistance is lousy, with 15-7 marginally better and almost equivalent to 316 (both have Molybdenum).

 

[OGMetEngr]

I meant 8%Ni for 304.

 

[EdStainless]

A cold worked duplex 2205 would have better corrosion and SCC resistance than a PH SS, but it would not be as strong.
There is actually a great alloy for this, SCF-19, but I don't think that you can get heavily cold worked bar in this grade. It is a high strength 6%Mo austenitic.

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Plymouth Tube

 

[Erkamal]

Thx My dear friends.

It will be helped to me