To "metengr" -A welding of Nitronic 60 question

[SSCGNB]

Your reply to another thread cought my attention.

I am looking for information re "overlay" welding N-60 on to the O.D. of a 20", 304sst "poppet" to achieve a metal-to-metal (valve) seal.

Also considered, welding N-60 bar (.25 cs) to edge.

Either approach would require post-machining.

Any thoughts/info appreciated, thank you

SSC

 

[metengr]

SSCGNB;
I would go with a 1/8" thick weld overlay deposit directly on the 304 ss versus a solid bar. For 20" diameter, use the auto-GTAW process with a boring bar or turntable for welding and machining. You can purchase the Nitronic 60 weld wire for the GTAW process.

Keep the interpass temperature during welding below 350 deg F, and after final machining, perform a Liquid PT.

 

[unclesyd]

Adding a little.

Here is a website with a lot of information on welding Nitronic 60.
Just be reminded that you will not achieve the same galling resistance of the wrought materials. You should get about 70% of the wear and galling resistance of the wrought product and maybe a little better on a good day.

http://www.hpalloy.com/Alloys/Nitronic60/Brochure/Welding.htm

Here is a source of the welding wire.

http://www.electralloy.com/weld_wire.htm

NITRONIC 60W (AWS A5.9-93 ER218)

 

[SSCGNB]

Thank you kindly for your input-SSC

 

[SMF1964]

Question for unclesyd - if you followed up the welding with a surface peening, would this improve galling resistance?

 

[unclesyd]

SMF
Interesting point that I don't have an answer for off hand.
When Nitronic 60 was first introduced by Armco we were one of the first to jump on the band wagon. At first Armco didn't recommend welding it so we used sleeves and solid pieces. It wasn’t too long until a consumables supplier (?Johnson?) in California offered a welding rod that would deposit the basic chemistry of Nitronic 60. Armco’s testing and our experience both came to the same conclusion that we didn’t achieve the wear and galling resistance of the wrought product. Far superior to the normal Austenitics but still less. Armco‘s research group laid the problem on the N2 distribution.

It is rather ironic that I never shoot peened Nitronic 60 as I shoot peened everything else. We achieved a lot by peening 304L SS and 316 SS. Probably I didn’t pursue this approach as we were achieving such good results in our primary applications with drums and sleeves for pumps and centrifuge parts at the time. We primally used Nitronic60/Nitronic60 and Nitronic60/17/4 Nitrided.

I have a lot of information on Nitronic60 and shot peening and I’ll check to see if the two have met.

 

[metengr]

unclesyd/smf1964;
I don't believe that shoot peening will enhance the wear/galling properties for this material. See the information below that was extracted from a technical brochure on Nitronic 60;

"The additions of Silicon and Manganese have given this alloy a matrix to inhibit wear, galling, and fretting even in the annealed condition. Higher strengths are attainable through cold working the material and is still fully austenitic after severe cold-working. (I would consider shot peening as locally cold working the surface of the weld deposit). This working does not enhance the anti-galling properties as is normal for carbon steels and some stainless steels. The benefit to the cold or hot work put into the material is added strength and hardness, and the wear resistance does not decrease noticeably. Chromium and Nickel additions give it comparable corrosion to 304 and 316 stainless steels, while having approximately twice the yield strength. The high mechanical strength in annealed parts permits use of reduced cross sections for weight, and cost reductions through the use of thinner stock."

Of course the best source to determine the affects of shot peening is to actually perform a galling resistance wear block test.

 

[unclesyd]

I have to concur that the only way to verify if peening will help welded N-60 is to try it.

Looking back through my notes and papers I found several references to discussions with Armco concerning the welding of wrought sleeves in place with 308L which resulted in the HAZ of the N-60 being a lot more susceptible to scaring if it touched off on startup. At the time it appears that this was an effect we had to live with and but was later eliminated by under sizing the ends of the sleeves by a couple of thousandths on the ends.

One of the things I had made a note to do was investigate these scars a little more. I made a note that the origin of the scars were anomalies in the wrought N-60, no mention as to what they were. Never got back to doing this as
N-60/17/4 (nitrided) started working so well for us.

I still think trying to peen welded N-60 would be a very interesting experiment. When I first started shootpeening every thing except what was the usual applications, I could get no help or encouragement, so everything was an experiment. I worked on surfaces, especially where the grain boundries were in play and achieved some very good results along with a few losers. In the process I used everything from a Wheelabator or Pangborn Slinger to a cleaning drum with chilled iron stars.

meteng,
I have essentially the same statements by Armco in several pieces of N-60 literature, but I would suspect that most of the references were to cold working in respect to forming. I can’t see getting the same surface modification intensity with normal cold work as you would by peening.

Wish I still had access to the my old lab as I would certainly have go at it.

 

[SMGNB]

To metengr and unclesyd:

Thank you for your replies on our question about Nitronic 60 overlay back in July. I am looking for some input on procedure or process for this overlay. We seem to be getting some conflicting information on the best process to do this "GTAW or GMAW". The base metal is 304sst and will be machined after the overlay for a seal surface. Any thoughts?

Thank you,

SM

 

[metengr]

SMGNB;
Either process is suitable. For a weld overlay on seal surface, I would probably recommend GMAW to obtain good deposition rates in the field. I remember reading in a technical brochure for this material that GMAW deposits have slightly higher strength than GTAW deposits because of reduced base metal dilution affects especially with the 304 ss or 316 ss. If you were going to fuse a solid bar of Nitronic 60 to 304 ss, GTAW would be preferred for autogenous welds.

 

[SMGNB]

metengr;
Thanks for the help!!