Damage and Tarnish on Inco625 parts
Damage and Tarnish on Inco625 parts
(OP)
Hi all,
My company uses Inconel 625 parts in a water spray nozzle. The nozzle sprays fresh water at around 80-90degC and 50-90psi. pH is pretty neutral. The suspended solids content of the water is less than 5mg/l and dissolved iron is less than 0.5mg/l.
Our problem is that we have had returned nozzle parts from customers with damage after less than 1 year. The part is a small disc, roughly 12mm diameter, with a 3.5mm diameter hole in the centre through which the water flows. There is evidence of corrosion/erosion on the inner hole edge, and a brown tarnish on the material. The tarnished area is still smooth and hard, no flaking or pitting.
I'm very surprised that we see tarnish and damage on Inco625 from spraying fresh water at pretty low temps and pressures. Anyone any ideas as to possible causes?
Thanks,
FP
My company uses Inconel 625 parts in a water spray nozzle. The nozzle sprays fresh water at around 80-90degC and 50-90psi. pH is pretty neutral. The suspended solids content of the water is less than 5mg/l and dissolved iron is less than 0.5mg/l.
Our problem is that we have had returned nozzle parts from customers with damage after less than 1 year. The part is a small disc, roughly 12mm diameter, with a 3.5mm diameter hole in the centre through which the water flows. There is evidence of corrosion/erosion on the inner hole edge, and a brown tarnish on the material. The tarnished area is still smooth and hard, no flaking or pitting.
I'm very surprised that we see tarnish and damage on Inco625 from spraying fresh water at pretty low temps and pressures. Anyone any ideas as to possible causes?
Thanks,
FP





RE: Damage and Tarnish on Inco625 parts
Any chance that they were running these at a lot higher pressure/flow than normal?
You can get cavitation damage on 625 orifice plates.
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Plymouth Tube
RE: Damage and Tarnish on Inco625 parts
There's always a chance of much higher pressure I guess, since the customer controls the water pressure. Generally they run at 50-60 psi, we state a permitted max of 90psi, but I would doubt if they ever even see 90 psi to be honest.
RE: Damage and Tarnish on Inco625 parts
Local erosion damage does not surprise me considering the size of the orifice you stated above. Have you calculated flow rates? You might be surprised at the velocity through the orifice at even 50-60 psi.
RE: Damage and Tarnish on Inco625 parts
RE: Damage and Tarnish on Inco625 parts
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Plymouth Tube
RE: Damage and Tarnish on Inco625 parts
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: Damage and Tarnish on Inco625 parts
We have seen this problem only on 2 customer units, and the major variable is the quality of the input water, so I had thought that it was likely to be a water-borne problem. Water samples we got back were within our recommended specs though, although there's no way to know if those samples were truly representative of normal running conditions.
The pipework feeding the unit is all 316SS.