Nitronic 60 sleeve and bushing

[haze10]

I am trying to select a sleeve and bushing material. Operation is a bottom auger for a large chemical vat processing paint pigment, 50% solids and water, somewhat abrasive. There is a large universal joint at the bottom that drives the auger. The cross of the joint has pressed on replaceable sleeves, the yokes of the joint have stationary bushings. 304SS is the auger and vessel material and it has held up well. The old sleeve and bushings were carbon steel 4140 Rc50. They have to run dry except for the water to avoid contamination. The 4140 would corrode badly. I am looking to go to Nitronic 60 for both the sleeve and bushing. Little concerned because the rockwell is only 20 on the Nitronic 60 and it can't be heat hardened. Loading is mild by the auger, the cross rocks about 15 degrees in the yoke, as the auger spins at 30 rpm.
Should I be concerned that both the sleeve and the bushing will be have low hardness.
PS, I am not a materials engineer but a mechanical engineer.

 

[lewtam]

Anyone have experience with this stuff? I've been keeping it in the back of my mind for the next time I'm in a similar situation to haze10 but haven't had a chance to use it yet.

http://www.brushwellman.com/alloy/products/copper_nickel_tin/adg6120.asp

 

[haze10]

We are soon to find out. I didn't mention that another option I was investigating was the Toughmet AT110. I am looking to do both the sleeve and the bushing out of this material. No heat treating, no grinding, no electroplating. Guaranteed not to gall as it is self lubricating. Hardness is Rc30. I am a little concerned about that. But, for now my problem is material selection is resolved. I had a one hour conversation with their metalurgist, who has seen other application to mine succeed with the toughmet. I have to do something, and if this does work it would be terrific to be able to do basic machining and thats all. In fact the guy said a profile finish anywhere under 32um is all I need. I should be able to do 22um in the CNC machine.

I plan to document the construction and installation of the parts, and how well they perform in the application. I will report back to everyone.

Thanks for all your help to date.

 

[unclesyd]

Don't worry very much about the hardness of materials like Toughmet, Stellite, Colmoloy, and others used in abrasive wear it really doesn’t have that much affect on the wear rate.

We ran a pilot plant with a conical mixer with a knuckle at the bottom that caused the arms to rotate. It was quite similar to the one at the GS URL below. As received, this knuckle suffered extreme wear until the moving components were coated with Tribaloy (800). Extremely expensive but very effective. The abrasive media was TiO2.


Mixer

http://www.globalspec.com/Supplier/Profile?vid=181948&Comp=2886&QID=

Tribaloy

http://www.stellite.com/wear_corrosion_alloys.asp

 

[EdStainless]

Hard coatings on stainless are a waste. The material is too soft to give enough support.

If it were me, I would use 440C vs Nit 50 or 60. Though the duplex 2205 actully works well as a bearing.

Any CS, it doesn't matter how it is surface treated, will corrode.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

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

 

[TVP]

For what it is worth, I agree with EdStainless. I don't believe that galling should be the biggest concern. Resistance to wear and corrosion are more significant.

 

[haze10]

Are you guys saying to just use 440C sleeve and bushing, and not worry about the galling. Would you use the same Rc on both pieces or alter them by 5 points.

 

[EdStainless]

The only reason that I suggest different materials is to reduce the galling. You can't get 440C hard enough to eliminate abrasive wear. It might be helpful to let one componant take all of the damage.
If you are using 440C for both, don't worry about the hardness. Just don't use tehm at their peak harness, Rc 50 should be plenty, and double temper. You want some toughness, it prevent microcracking.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

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

 

[unclesyd]

440C is good choice to try, but I would raise the hardness.
Based on my experience 440C at 50 Rc will not offer very good abrasive wear resistence. We have knives made from 440C cutting a very abrasive polymer and the higher the hardness, > 58 Rc, the better the wear resistence by several orders of magnitude. There is not need for a hardness difference.
Again based on my experience and limited literature on 440C the galling threshold is fairly low in a self-mated couple. This may or may not be consideration as any liquid will act as a lubricant and greatly improve the galling and wear even though it may contain the abrasive.

You might want to look at 440XH SS from Carpenter. This alloy is capable of higher hardness while maintaining the corrosion resistance of 440C. What little experience I’ve had with this alloy it was looking very good in some of our applications on both the wear and galling aspects.

 

[haze10]

I spoke today with the person who originally developed Nitronic 60. We had a long discussion about the application and discussed all of the above choices. He had some interesting comments about wear versus hardness. Not being a metalurgist I could not keep up with all of it, but basically his comment was that when dealing with stainless hardness does not necessarily directly relate to wear resistance. Also, he stated that having different hardness on self mated stainless had little real benefit. One interesting experiment with 4140 revealed a 10 fold decrease in wear by going from a Rc50 to Rc52. But N60 with a rockwell of 28 would have significant less wear then 17-4 or 416. Apparently some of the softer alloys will 'work harden' to what he claims is approx Rc48. He basically stayed with his data in the N60 brochure and recommended N60 self mated for reduced wear, but said if cost was an issue to go with N60 and 316 or 304. His recommendation on finish was the finest cut available on a CNC machine, and that his tests showed that a very fine ground surface promoted galling.

So now I am going to run two tests, one with Toughmet self mated, and the other with N60 self mated. When buying N60 shop around, for a 3.5" x24" round bar I was getting prices from $450 to $1100, with HP Alloy being the lowest. The N60 like the Toughmet will require only machining, no heat treating, no grinding, no plating. If it works it will be a big advantage.

 

[CFUltraTech]

Haze,

Another place to try is Baldwin International. They supply specialty steels specifically for abrasive wear applications and have a good knowledge of various applications and propoerties relating to hardness, work hardeneing and machinability

I have some contact info for one of thier reps if interested.

 

[rorschach]

Haze, personally I would NEVER consider self-mating one stainless with another where galling could be an issue, in fact self mating is never a good idea when galling is an issue, regardless of the specific material, not even N60, which as stainless goes is quite gall resisitant. Galling is for all intents and purposes solid state welding. high points (asperities) on the mating parts get mashed together and they weld to each other and are then torn apart again, leaving an even rougher surface for yet another welding cycle, over time (often short) these welds get larger and larger until they are large enough to cause things to sieze up. to avoid this, mate ing parts with dissimilar crystalline structures, FCC for steel and HCP for copper alloys for instance, and not just hardnesses, is always an excellent idea. Your best bet would be toughmet or Ampco 45 (aluminum nickel bronze) mated to N60 IMHO.

 

[haze10]

I understand and share your concerns. But over the course of this investigation I have had so many contracting opinions that I eventually had to just make a decision and decide on a course of action. Like I said, I spoke with the original metalurgist that developed N60 and the person who had conducted extensive testing of the product self mated and with combinations. His conclusion was to selfmate N60, and or N60 and 316, and after continued probing of which was best, he concluded N60 self mated. He didn't have any data on N60 and Toughmet. The metalurgist from Toughmet had data on Toughmet self mated and also swore that they have had extensive and successful experience in this application. He felt so confident that it would work, that he gave me a $1000 sample for free. Both people want a profile in the 16 to 18 um range, or a fine machine finish. I'd rather go with recommendation of materials that have been tested. In this case they have both been self tested. Neither had been tested in combination with each other. Should I have just made one of them out of 316 and then used either of the others for a combination. Well, maybe. But this would be against their recommendation and I have to assume they know what they are talking about. This material science stuff is more like law than physics. Everyone has an opinion and you can't find the truth. Most of the metalurgists I spoke with at the mills, were just going through their handbooks to look up galling rates and wear rates, I didn't get the impression that they had any real machine building experience. I should be doing the machining next week, and then we will see. I found this board to be the best help of all!!!!

 

[Tmoose]

Cronidur 30 ? All my info is anecdotal, and FAG provided my paychecks for several years. Generally used with at least a hint of lubrication, but your corrosion issues made my ears perk up.

http://www.emeraldinsight.com/Insig...blished/NonArticle/Articles/12773aad.014.html

http://www3.interscience.wiley.com/cgi-bin/abstract/69502828/ABSTRACT?CRETRY=1&SRETRY=0

http://www.umbragroup.it/Aerospace/Products/template?id_cat=Cat20

 

[haze10]

Cronidur 30 sounds like a very interesting material. But my first thought is that it sounds difficult to machine if it is like 52100. How hard is the machining? What is the Rockwell without heat treating. What is the heat treating and final hardness. Final, have any idea of cost?

 

[ornerynorsk]

What about D2. It's a heckuva lot cheaper than 440C.

 

[NickE]

Ornery- Haze doesnt want to grind at all...

 

[ornerynorsk]

NickE, the kind of clearances we're talking about, there shouldn't be any need of grinding. D2 is pretty stable during heat treatment. Ya know what else guys? Grinding and honing isn't as expensive as you make out to be. This is just another urban machineshop legend.

 

[NickE]

Ornery- I agree, just letting you know he'd already been led down that path, and balked...

 

[haze10]

I made two sets, one out of Toughmet and the other out of N60. I will be installing the Toughmet set first. Then a few weeks later I have to overhaul and identical drive unit and I will install the N60. Then periodically I will perform inspections and check for performance. For anyone interested, and being that so many people have responded to help me on this, I will soon start two new threads, Toughmet and N60, with some photos and impressions on machining capability, finish, fit, etc. Not sure if I can, or know how to post photos. So if anyone can guide me I would appreciate it.