17Cr-4Ni-4Cu properties to resist H2 embrittlement 2

[Xianglu]

Hi Gents:

Would anyone suggest 17Cr-4Ni-4Cu (UNS No S17400) properties to resist H2 embrittlement under elevated temperature and pressure, please?
Application pressure is 260 psig at a temperature of 950 deg F.

Thank you in advance.

Henry

 

[unclesyd]

Your temperature is way too high for 17/4 PH. The normal recommender max temperature is 600°F.

 

[metengr]

Agree with unclesyd. The max temperature for this material permitted by ASME Boiler and Pressure Vessel Code is 650 deg F.

 

[Xianglu]

Many thanks unclesyd.

Here is the revised application condition:
total P: 220 psig
H2 partial P: 127 psig
Temperature: 753 deg F.

Is it suitable? if not would you please provide reasons?
Thanks again.

 

[metengr]

Xianglu;
What is your specific application - a pressure vessel?

Above 650 deg F, the strength of 17/4 PH in Codition H1150 drops appreciably, which is the reason that the Boiler and Pressure Vessel Code committee limits this material/condition to 650 deg F max.

If you want more information on this material and the affect of elevated service temperature, see the web site below and look for the tech bulletin on 17/4 PH;

http://www.aksteel.com/markets_products/stainless.asp

 

[unclesyd]

17/4 PH when exposed to temperatures above 600?F to 750?F long term loses ductility, with a slight gain in strength. In this temperature range some of the ductility can be restored by an H1150 heat treatment. Above 750?F the loss is greater faster and there is less recovery from the additional heat treatment. You supposedly can do this indefinitely, based on my experience I think there is a point of no return in this procedure.
We started using 17/4 PH shortly after it's introduction to replace the CrMo alloys with their heat treatment requirements. Early on it was discovered that our parts were getting harder, easily determined as we had the thermal history on each part. It was also determined that we had lost some impact resistance evidenced by some in service failures we experienced.
Our process required us to thermal cycle the parts between our operating temperature of 550?F (500 hrs) to 900?F (8 hrs) for cleaning. In addition some parts set in a preheater at 600?F (up to 200 hrs). After approximately 20-25 complete cycles it was almost impossible to machine, drill and tap for HeliCoils, the parts without an overaging heat treatment. The lost of ductility manifest itself by losing thread in tapped holes.
It was too long after its introduction that the maximum use temperature of 17/4 PH was set at 600/650? F. You will note that nearly all the PH alloys have some maximum temperature limitations in this range.

Anecdotal:
Very recently I learned that a fastener material substitution was made in steam turbine operating at 750?F and 12,500 rpm. The set in stud fasteners coupled the disk to shaft through a Curvic Coupling. The original fasteners were Waspaloy and the change was to a PH material. I happened to catch this almost at the beginning and was able to alert the owner of the turbine. They took about two months of soul searching to start to understand that they had a potential problem. Last week the turbine wheel was examined and while removing one of the studs for testing it broke under very light load. In all 3 of 8 broke.

 

[EdStainless]

950F and high pressure hydrogen, I suggest that you work with austenitic alloys. How much strength do you need? You may end up with a Ni based alloy.
Yes, it will cost more, but it will work.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[Xianglu]

Thank you ALL! metengr, you always give me so much help. Thank you again.

My specific application is a machinery part with internal pressure. The part requires the following features:

1. High stiffness to resist deformation;
2. High hardness to resist wear rate
3. High corrosive resistance to traceable O2
4. Suitable for Hydrogen service as defined above.
5. High temperature properties under 753 deg F.
6. Resistance to cyclic service in both pressure and temperature, in 10th of millions of cycles.
7. Potentially in compliance with ASME code as a pressure vessel component.

If you would please advise what are the best material candidates, it is very much appreciated.

 

[mcguire]

Why don't you check out A-286? This is the only austenitic PH grade and it exists to overcome the temperature limitations of the other PH grades.

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/

 

[metengr]

Xianglu
Regarding your list of demands, for item 7), I would definitely use ASME Section VIII, Div 1 as a design basis for this cylinder (especially at 260 psig pressure).

Once you have established the design basis under ASME B&PV code, Section VIII, Div 1, you have a range of ferrous and non-ferrous alloys to choose from to achieve the rest of your demands using a maximum design temperature of 800 deg F.

For your stated service conditions, a Cr-Mo alloy (Grade 22), in addition to the austenitic and Ni-base alloys are suitable for hydrogen service at this pressure and temperature. So, you have a wide selection of alloys. For item 1) you can increase wall thickness to increase stiffness of the cylinder.

For item 2), I am not sure what you mean by high hardness to resist wear - is this a gas medium or liquid medium in this cylinder? What is the wear phenomenon?