Material Combination

the maximum speed of operation is 500 mm/min and minimum speed is 50 mm/min. the contact pressure is of the order of 10 MPa.

Teflon.

Your question is too vague.

What are you trying to do?

There are almost unlimited number of materials.

Perhaps give IGUS a call and discuss your application with a Techie:

http://www.igus.com/iglide?C=US&L=en

Massey,

GA

You beat me to the punch.

IGUS has a ton of plastic bearings that would work.

Consider Frelon.

It's Teflon based, but stronger and more slippery.

It can handle 10 MPa, is almost totally chemically inert, is self lubricating and can handle surface speeds in excess of 40 metres/min.

The base metal is of no consequence. It's the chrome/bronze friction that is of interest.

The most obvious is a lubricant. Either oil or powdered spray on TFE. MS 122 comes to mind.

You do have search engines in your country, don't you? Type your requirements in the site given below:

• 
  
• Products & Suppliers
• 
  

it is by and large under water application and probably no lubricant can be used. I need a metal-metal combination that shall work with heavy water as the medium and also it shall work fairly in dry condition when the water is drained. And no plastic can be used in the working zone due to radiation issues.

That information was needed in the original post. :-(

Are you looking for a bush material alternative or a residual lubricant.

alternative bush material as there is no chance of changing the lubricant from heavy water.

Sorry, did you actually mean heavy water? If so, what's the application?

https://en.wikipedia.org/wiki/Heavy_water

Yes. Heavy water is the medium. There is a carriage, with AL-Bronze bushes, which moves up and down carrying the spent Uranium Fuel bundles. The guides that are positioned diagonally opposite, are of chrome plated 17-4 PH material. Around 120 microns of gap exists between guides and bushes, but due to uneven loading or some such condition, It is observed that the frictional resistance is giving jerky movement to the carriage leading to more requirement of driving force. we wanted to change AL-Bronze bushes to some other material that could give lesser frictional resistance as well as compatible with Heavy water medium, at the same time it shall work well even in dry condition.

Some sort of roller bearing or ball bearing?

This forum really hates games of "20 Questions".

i could not get a stainless steel roller bearing that could fit in 10 mm of space.

Check out the IGUS website. They do impregnated polymer bearings and have a fast turnaround service where they will machine a bearing to your specific requirements.

UHMWHDPE may be the most suited for this application.

No plastic like PTFE, Frelon etc. is allowed in the radiation environment. The radiation is of the order of 10000 Rad, so we can think of using only metallic bushes. For example, Phospher-Bronze etc.,

How did the phosphor bronze bushes work?

PTFE loses its propeties substantially in the radiation environment at that Dose rates and becomes brittle and hard, whereas the metals don't get to such level of uselessness though the properties slightly change. Bronze bushes would work even at the fluence.

Try the bronze bushes then.

AL-Bronze bushes are already there and giving 0.4 to 0.6 coefficient of friction. My idea is to find any other material combination that could drastically reduce the friction to may be 0.1-0.15.

Instead of Al Bronze try a different bronze. There are many types.

Can you change the rails? What is the rail material?

Instead of changing the bushings why not add more to the carriage? Diagonally opposed anything on a slide leads to problems from the start. If the weights differ from side to side, draw bar/chain/belt/cable tension variation, lubricity, heat, etc.etc. will cause binding in the bush and being diagonally opposed will exacerbate the issue.

Just add more bushings and let it ride.......so to speak.

the bushes are placed diagonally as set. please refer the drawing below.

Consider changing both the rail and the bearing material. Cast iron on cast iron has a sliding friction coefficient of 0.15 when dry. Intuitively I would say that any lubricant, including water, would improve that but the only figure I can quote is grease which drops it to 0.07. The dry static friction of cast iron on cast iron is 1.1 so you may need more umph to get it started. Alternatively can you add anything to the heavy water to improve it's lubrication properties?

to have corrosion resistance in under water application, the rails are stainless steel (17-4 PH).We can't change it to cast iron.

Does the binding also occur when submerged or only when dry?

the behavior appears to be same in both cases.