Extrusion Barrel Corrosion 3

[quark]

We are planning to use this Machine for extrusion of one HCl compound. The highest temperature zone is 180C and immediately cools down to 90C. Presently, the barrel MOC is X15TN and got corroded after taking some trials. Barrel is made of SS316 and the product contact sleeve is with X15TN. The manufacturer is suggesting 17-4PH as they need minimum hardness of 44 HRC. Even this material doesn't seem to be good for pitting corrosion. Request your suggestions on this or any other better material.

My search indicates X15TN to have better pitting corrosion control. I checked PRN for X15TN and is about 22.5. Usually,is this a better value?

 

17-4PH won't buy much corrosion resistance. Being martensitic it will be inferior to 316L for sure. What is X15TN, a PH stainless?

The environment you describe is nasty; I recommend you locate or develop some basic corrosion data for the HCl compound (I'm not sure what that means, but it can't be metal-friendly).


"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[MagBen]

17-4 will be worse in terms of corrosion, lower PREN. Also, in order to get a min 44RHC, you will have to HT to H900, then you have SCC concern. 17-4 won't be a good choice.
316L is bit higher PRN than X15TN, but i do not see much chance to get a min 44 RC.
you may try Nitronic 50 with PRN about 33, but you will need to heavily cold work to get the hardness level.
For both mechanicals and corrosion, you may also try high temp alloy, say Inconel 718 with a PRN up to 30.

 

[quark]

Thanks ironic metallurgist and MagBen for the responses. X15TN (S42025) aka surgical steel is not PH stainless. The product extruded is a hydrochloride compound. I checked for Inconel 718 and the data shows hardness is 100 HRB, so on scale C it is about 22. Not sure whether this can be an alternative. Any surface preparation or cathodic protection suggestions?

 

[MagBen]

You will have to do precipitation hardening HT to get the hardness. 44RC shall not be difficult to be obtained for 718.

 

[EdStainless]

HEAT TREATMENT
The heat treatment consists of solution treating followed by a double aging treatment. Depending on the mechanical properties desired, one of the following two heat treatments is utilized:
• For optimum impact properties:Solution treat at 1,950° F (1,066° C) for 1 to 2 hours. Air cool. Age at 1400° F (760° C) for 10 hours. Furnace cool to 1,200° F (649° C). Hold for total elapsed time of 20 hours. Air cool.
• For optimum tensile and creep-rupture properties:Solution treat at 1,700-1,850° F (927 - 1,010° C) for 1 hour. Air cool. Age at 1,325-1,400° F (718 - 760° C) for 8 hours. Furnace cool at 100° F (38° C) per hour to 1,150-1,200° F (621 - 649° C). Hold 8 hours. Air cool.

As I recall the spec min after aging is 180ksi/150ksi, we typically see 200ksi/175ksi with 20% elong.

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P.E. Metallurgy

 

[quark]

Thank you guys for the response. Working and searching on this for the past week. There is a definite issue with high Nickel content materials with this application. I am still checking my options. Will post once decided and checked.

 

[LUengineer]

Check AMS 5898 for incrementsl corrosion improvement versus x15tn at like hardness.

 

[TugboatEng]

If you can't use nickel but you need acid corrosion resistance would this be a good application for one of the titanium nitride coatings on a high nickel substrate?

 

[quark]

Thanks for the response. I will check these options.