Elgiloy vs. Inconel 718 for 17% H2S service, 4

[bogiedreamer]

I have two spring materials to choose from for use in a spring energized seal but not sure if Elgiloy or Inconel 718 will be better in term of better resistance to corrosion because of the present of H2S at 17% conc.

Could you please give some advice? If possible, please include source of information.

Many Thanks,

 

[TVP]

Springs for direct exposure to H₂S can be made of Elgiloy (UNS R30003) in the cold worked and aged condition up to 60 HRC maximum. Alloy X-750 (UNS N07750) can be used up to 50 HRC maximum. Alloy 718 is not recommended for springs. Source: NACE MR-0175 and ISO 15156-3.

 

[grampi1]

Elgiloy is a good choice. We would not use X750 in 17% H2S. Several failures of X750 can be found in NACE papers.

We also have had one Elgiloy spring failure in highly sour service. We think it was over cold worked and was near strain exhaustion as new.

Who checks hardness of thin flat Elgiloy springs to confirm they are below 60Rc?

 

[bogiedreamer]

Guys,

Thanks for your advice. So it is not benefitial to heat treat the Elgiloy for high conc. H2S service because it will increase the embrittlement?

We like to heat treat our Elgiloy springs to improvement yield's strength but I am not sure if heat treatment could hurt in the case of high conc. H2S service.

B

 

[EdStainless]

Use Elgiloy
heat treatment is fine, but you need to know how much it was cold worked before so that it doesn't end up too hard.

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