CA6 NM Operating in Hydrogen Gas Environment 2

[metwd3]

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)

 

[Guest102023]

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.

 

[metwd3]

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

 

[arunmrao]

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!

 

[metengr]

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.