Spring failure

[Pras]

NOTE :- SAME POST IS REPEATED IN 'CORROSION ENGINEERING'

Pras (Mechanical) Aug 9, 2002
Hi,

We are facing failure problems of a springs made up of SS316L material ( 1.0 mm wire diamter, 6.3mm outer diamter, 9.5mm length)which are used in our special pipe fittings. The spring is exposed to the fluid and supposed to work in 'compressed condition'. It is clear from our observations that the fluid ( Saturated steam at 200degC in this case) is attacking the spring material and causing it to break in pieces. The microscopic examination of the spring pieces indicate the presence of 'brittle cracks' within the piece, which we believe could be due to corrosion attack. It has also been confirmed by the customer that he is adding some additives like chemicals / powders as ‘descaling agents’ in the boiler feed water. This could be the cause of ‘Corrosion’

I am planning to change the material of construction of these springs to Hastelloy –C ( Grade C-276) to increase the corrosion resistance.
Now my questions are :-

(1) Is Hastelloy –C ( C-276) material suitable for springs ??

(2) Do we need to provide any heat treatment (oil hardening and tempering ) to the spring wire before coiling ? One of the spring manufacturers informed us that this heat treatment would be required to avoid problems like ‘Permanent set’ in hastelloy-C springs.

(3) Any other material of construction for this application ???

Please advise.

Thanks in advance.

Pras

 

[lgearhart]

Pras, I hate to sound like a commercial, but why not use elgiloy? I's a cobalt-chromium-nickel-molybdenum alloy that has superb corrosion resistance in a lot of (though not all) chemical environments, and it's a spring alloy, readily available in wire. Talk to Terry Bartel at 847-683-0500, terryb@elgiloy.com, for advice on compatibility with your suspected corrosives. He'll also tell you how to age it (usually 900F for 5 hours) for maximum strength, or could likely tell you a source of the springs you would want.

Good luck!

Lee