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Nitronic 60 sleeve and bushing

Nitronic 60 sleeve and bushing

Nitronic 60 sleeve and bushing

(OP)
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.

RE: Nitronic 60 sleeve and bushing

I would not replace hard steel bushing with any type of soft one in abrasive application. The soft (304) auger might survive because the abrasives are not working in a narrow space (like the sleeve does.)

I would suggest SS like 420 or 440B/C hardened near 50Rc.

RE: Nitronic 60 sleeve and bushing

How about using Stellite facings for wear and corrosion resistance.

http://www.stellite.com/

RE: Nitronic 60 sleeve and bushing

(OP)
Here is the problem.  The equipment requires annual maintenance.  We are getting about 9 months service out of the 4140 Rc50 bushing and sleeves.  They appear to be subject more to corrosion than to wear.  My goal is to try to get 18 months   service to guarantee it makes the one year service interval.  Because they are replace frequently, I don't want to go for anything too exotic or expensive.  Clearances are on the loose side.  The ideal would be to select a material that can be turned on a CNC machine, to a profile of say 30um and not require grinding or heat treating.  The sleeve is pressed on the cross with 0.001 interference.  Sleeve and bushing have about .005 to .008" clearance.  If I go with material that displaces with heat treatment, than the components have to be remachined.   So then its rough machining, heat treating, and grinding.  Driving the cost of each piece over $100.  The Nitronic 60 brochure states that wear is not changed with a profile from  6 to 30 um, and that the self mating pieces will not gall with 50kspi pressure.  Wear is also very low.  

Researching all the stainlesses, they all have very low galling thresholds, even 17-4 when hardened to 42Rc.  One person suggested I try 17-4 annealed and machined to fit at Rc28 on one piece, say the bushing, and 17-4 H950 at Rc42.  He claimed that the 12 point difference in hardness would prevent galling.  But I can't find any literature to support that.   

The other option is to stay with steel, like 8620, carburized to Rc60, then ground.   While this may be a better bearing surface, the corrosion would probably be the same.   

Is there any ideas out there to help me.  Coatings are just to expensive and time consuming.  Often the bushings have to be in a couple day for emergency repairs, and while close they are not all identical.  I need a material that can be handled and the local machine shop, preferably without heat treating and grinding.  Carbon or SS is acceptable.

Here's the link
http://www.hpalloy.com/DataSheets/ni60.htm
just below the title click, see full brochure.

thanks again to all you experts.

RE: Nitronic 60 sleeve and bushing

My first thought is similar to alexit-- a martensitic stainless steel like Type 420 or 440C.  Both can be quenched and tempered to 50+ HRC.  You can obtain more information from the following links:

http://www.alleghenyludlum.com/ludlum/pages/products/xq/asp/P.81/qx/product.html

http://www.alleghenyludlum.com/ludlum/pages/products/xq/asp/P.84/qx/product.html
Click on Technical Data Bluesheet for both of these links

http://www.timken.com/products/specialtysteel/engineering/tech_info/PDF_Files/vac_arc/Bearing/440%20N-DUR.pdf

http://www.cartech.com/

RE: Nitronic 60 sleeve and bushing

(OP)
The 440 looks interesting.  But what about galling.  Would you make both the bushing and the sleeve from the same material, and would you harden them to the same rockwell, or to different rockwells.   How much dimension change would you expect after heat treating.  What finsh profile would you recommend.

RE: Nitronic 60 sleeve and bushing

440 is typically air-quenched, if you can live with 0.03mm distortion during heat treatment this would not require secondary operation.

Galling will always be problem if both are same material and operating poor lubrication. People who say to keep hardness very different to prevent galling are having different experience than I, we always get galling problem no matter what.

Other idea is what you say to 8620, carbonitride or such and secondary finish. We found for corrosion: get good core hardness (~Rc30), finish operation (we like hard turn in this range), then gas nitride (do not machine white layer after this), corrosion resistance and wear is very good, even better than 440. Problem for us was the distortion from last nitride. Maybe this work for you?

Is sleeve or bushing more problem? Do one in stainless and other in 8620 like written, solve galling and give trial for both materials...

RE: Nitronic 60 sleeve and bushing

I like the thought of using Nitronic (or any high Mn, high N stainless, like 201LN) for one member and 440C for the other.

With the austenitic stainless grades that show some wear and gaulling resistance, the reson is that they surface work harden a lot in service.  When we cold draw tubing in those grades we can get over 150ksi UTS and mid 30's Rc without any trouble.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.
http://www.trent-tube.com/contact/Tech_Assist.cfm

RE: Nitronic 60 sleeve and bushing

(OP)
What about mixing the SS.  Say use 440C for the bushing and 420HC or 416 for the sleeve to reduce galling.   The bigger problem has been the stationary bushings.   But both the sleeve and bushing show signs of wear and corrosion, just a bit more on the bushing.  Then is when using the 4140 Rc50.
The stainless idea would definately solve the corrision problem.   Using the 8620 and carburizing, finish cutting, and then nitriding it getting to expensive.  Plus trying both doesn't prove that when self mated it would work (for the 440C).   This is not a high load condition, I may get away with the SS not galling if I pick the right combination.  440C and Nitronic 60 show no galling to 50 ksi, but I am skeptical of the softness of the nitronic 60.

RE: Nitronic 60 sleeve and bushing

(OP)
The other idea is to go with carbon steels, 4140 or 8620, carburize or heat treat, finish grind, and then electroplate hard chrome to 2/10" of .001"   I could also do this to the 440C if that would stop the galling.

RE: Nitronic 60 sleeve and bushing

Maybe one of the really high chrome tool steels?
(just a brainstorm thought, D7 chemistry says 11.5%-13.5%Wt-Cr -- almost stainless)

RE: Nitronic 60 sleeve and bushing

NickE,

The Cr is all tied up in carbide form.  Not stainless at all.

RE: Nitronic 60 sleeve and bushing

(OP)
Guys, I'm still lost.   
440C, 416, Nitronic 60.
440 and 416 have a higher resistance to gall than 440c self mated.   416 and 316 is even higher.  But the 316 may be too soft.  If I went with 316 I could as easily go with the N60.   

Slow rpms, moderate load, abrasive, run dry, simple and reasonably priced.   

If I can't feel reasonably comfortable on a decision I have to revert back to 4140, and that was not really the best choice.

RE: Nitronic 60 sleeve and bushing


haze10  Why not consider attaching a zinc anode so that it is in electrical contact with the universal joint?
That should alleviate galvanic corrosion which is probably occurring between the submerged part of the 304 auger and the 4140 universal joint, and at least let you select mechanically durable bushings and pins.

RE: Nitronic 60 sleeve and bushing

TVP- thats what I always thought, I had however heard some admittedly anecdotal reference to using the D-type tool steels in applications requiring light corrosion resistance. (Though that may have been in relation to A-type.)

RE: Nitronic 60 sleeve and bushing

(OP)
Tool steel isn't the answer either as its too difficult to machine conventionally.

The easiest is N60 versus N60, straight machining, no grinding, no plating.

Next is N60 bushings versus 440C Rc60 sleeves.  I have to heat treat and grind the sleeve, but the bushing is still just lathe turned, no plating.

Next is 440C Rc62 sleeve, versus 416 Rc53 bushing with 2/10" flash chrome.   both pieces have to be machined, heat treated, ground, and the bushings chromed.

Next is 4140 or 8620 through hardened to Rc55,   machined, heat treated, ground, flash chromed.   

As you can see the N60 v N60 would be the simplest and cheapest way to go, but there is no telling how the relatively soft N60 would hold up to the grit, and to the physical loading.  But I do believe the loading is relatively light as there is not great resistance in turning the auger in the slurry.

Help!

RE: Nitronic 60 sleeve and bushing

Ha, my last post never made it...

For to address galling issue, try 8620 turned bushing and gas nitride (do not machine white layer), corrosion resistance can be better than 440 and wear is very good as surface hardness Rc70. Do sleeve as 440C turned and then heat treated to Rc55. Geometric distortion of both 8620 and 440C should be less than 0.03mm from heat treat is this problem?

RE: Nitronic 60 sleeve and bushing

(OP)
I would have to grind after heat treating.  So the nitride coating would be removed.

RE: Nitronic 60 sleeve and bushing

how about Kohlsterizing some 300 series? would that prevent galling?

RE: Nitronic 60 sleeve and bushing

(OP)
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.

RE: Nitronic 60 sleeve and bushing

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

RE: Nitronic 60 sleeve and bushing

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

RE: Nitronic 60 sleeve and bushing

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.

RE: Nitronic 60 sleeve and bushing

(OP)
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.

RE: Nitronic 60 sleeve and bushing

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

RE: Nitronic 60 sleeve and bushing

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.  
  

RE: Nitronic 60 sleeve and bushing

(OP)
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.

RE: Nitronic 60 sleeve and bushing

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.

RE: Nitronic 60 sleeve and bushing

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.

RE: Nitronic 60 sleeve and bushing

(OP)
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!!!!

RE: Nitronic 60 sleeve and bushing

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/Insight/ViewContentServlet?Filename=Published/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

RE: Nitronic 60 sleeve and bushing

(OP)
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?

RE: Nitronic 60 sleeve and bushing

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

RE: Nitronic 60 sleeve and bushing

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

RE: Nitronic 60 sleeve and bushing

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.

RE: Nitronic 60 sleeve and bushing

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

RE: Nitronic 60 sleeve and bushing

(OP)
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.

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