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CA6 NM Operating in Hydrogen Gas Environment
2

CA6 NM Operating in Hydrogen Gas Environment

CA6 NM Operating in Hydrogen Gas Environment

(OP)
I am planning to use CA6NM heat treated to Brinell hardness of 300 – 350 HB for compressor casing and rotating elements to handle hydrogen gas of 85% to 99.9% purity.  I would appreciate receiving any information or experience in using CA6NM or similar materials in hydrogen gas environment.

Thank you.

Metwd3 (Materials)
 

RE: CA6 NM Operating in Hydrogen Gas Environment

Temperature & pressure?

FYI, if you ever need help welding this stuff, I can - it is my signature alloy, from my days in the hydro turbine business.   

RE: CA6 NM Operating in Hydrogen Gas Environment

(OP)
Thank you brimstoner. The temperature and pressure is 40-70 C and 200 psi respectively. The rotating part can be stressed up to 70% yield. I am concerned about potential hydrogen induced cracking.  As far as welding is concerned, the foundry may need to perform weld repair of casting defects.

Regards,
metwd3

RE: CA6 NM Operating in Hydrogen Gas Environment

metwd,

In my opinion hardness of 350 BHN is high if you need adequate toughness. Those with hydro turbine castings will support me. Double temper and have your hardness in 240-260 BHN range,then All is well!

RE: CA6 NM Operating in Hydrogen Gas Environment

There should be no hydrogen induced cracking in service if you are moving hydrogen gas at the stated service temperature and pressure. I would agree with arunmrao regarding the hardness range for the casing, since this is a static component.

The rotating element may require further evaluation regarding choice of material and suitable tensile yield because I would not design using 70% of tensile yield for this type of application. What about fatigue from torsion and bending?

I would determine the service stress (considering dynamic and fatigue loading conditions in service, adequate toughness) based on analysis of the rotating elements and from there decide on material selection using a minimum strength level containing a proper design factor.
 

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