Hoe big is your machine and how do you want to assemble the sliding surfaces?  There are all types of materials, cast iron, bronzes that will work so come back  with a little  more information.

Hi UncleSyd!

The side plates (frame components) of our machine are a few square meters (app. 2.5 mtrs high and 2 mtrs wide, and app 100 mm thick). Sliding surfaces are on cut-outs of these frame components (not the face side, but the 100mm wide side).

Bronze is no option; cast iron too expensive for the small number we'll produce. Steel plates might bee the best. But what?

Thanks!

I assume this frame is going to be weldment. All the normal construction materials are going to have the same wear resistance and generate the same amount of friction.  What is the moving component made from?

They are some alloys available that work harden and at the same time improve the wear and friction properties.  What part of the world are you as most of these material are not generic?  
Hate to give something not available in your area.
 
What is the load, weight/per unit area, of the sliding component?

Will you be able to finish the contact surface?  If not would it be possible to weld/overlay  a better  wearing/hardfacing  material to the wear area and machine to dimensions?

What is the shape of the contact surface, flat, vee, rails?

Hi UncleSyd!

The components we're actually discussing about are flat sliders, app. 500 mm long and 100 mm wide. Total load is approx 200 kg / slider; two sliders move simultaniously, approx. 5 mm / sec. Movement is not continuous; only once every 2 hours (machine adjustment).

Material of moving component can be chosen freely, but also possible to use special something.

High resistance agains wear is important, due to fact precision is required (printing industry).

There are two possibilities: either we use the steel frame components as sliders (disadvantage: not possible to machine as smooth and precise as we want) or we use special sliders bolted to the frame.

The region is South-East Asia.

Thanks a lot!

Frankieboy

I prefer your suggestion to use a special slider piece bolted to the main structural frame.  Several advantages; the main frame can be made from a less expensive structural steel to suit the loading;  any wear will not impair the structural integrity of the frame; the slider can be made from a more suitable (i.e. expensive) material then machined and heat treated to suit the end use;  if the slider is less than perfect it can be upgraded relatively inexpensively;  when it wears it can be replaced relatively easily;

Hi macmil!

You are right!

But what material to use?

The ideal material would be Cast Iron, depending on how it's loaded, sliding with/without gibs, guided roller, or plain sliding.  If the configuration allows the CI should be flame hardened on the bearing surface.  The next choice would be Bronze, again depending on how it's loaded.
There are people who supply guides and ways made of both of the above materials.
I would also look at a through hardened tool steel, D2 or A2 bolted on.   
There is also the possibility of a Liquid nitrided piece of steel.
All bolt on materials would require a smooth flat mounting surface.
I'll look around for some information on purchasing guides and ways.

     

Cast iron will be the first choice as the graphite flakes provide lubrication to the sliding surfaces. Also you can flame harden the surface. Cast iron lends itself to scraping excellently.

Any other choice will definitely be a compromise on one or more of these factors.

You can locate a few machine tool casting manufacturers in India who will not mind small volumes. The approximate cost can be 0.8-0.9$ per kilo for cast iron casting apart from the tooling cost.

Would this advice also apply in case one of the mating surfaces would be cast iron and the other just machine frame steel (low cost)?

This is easier for manufacture / assembly.

This would be better than steel on steel and depending on how the load is applied it might do very well.

Try to get as much contact area as possible to distribute the load over a larger area.

Are you going to be able to lubricate the sliding area?

Hi Unclesid!

Thanks for reply!

We'll lubricate, but problem is in daily life, greasing is often neglected, so best to have dry-run possibilities.

Is hardening required?

Frankieboy

The wear properties get pretty complex with the CI vs Steel.
You would normally want the CI flame hardened (>250 Brinell) vs steel.

If you can harden a piece of steel and bolt it to the frame the better off you are. You are not going to have velocity in play, only sliding wear, so if you could get a hardened bar for the CI to mate with the CI could be left unhardened.  I would still flame harden the CI in either case.

A fine pearlite matrix is the best for wear.  A high combined carbon, as pearlite, is the way to go.

Have you thought about using linear ways? How precision does your motion need to be? Machine tools have been built for years using roller bearing techology and previously Turcite sliding surfaces on both cast iron and steel and the oldest method is cast iron on cast iron.
Cast iron can be purchased in a continuous cast bars either round, square or rectangular to be used for rails or sliding surfaces (Durabar).

Frankieboy,

I may have missed the point but I think you need to slide two surfaces with a moderate loading, preferably without a requirement for lubrication and with minimum wear.
I have used stainless on carbon steel (and even Low Alloy on low alloy but I would not recommend it)in simílar situations. It is very noisy but does the trick. The second option is to use DEVA material a self lubricating sintered material which we have used at 500 ° C and above.(I think the company is now owned by Federal Mogul) but a large plate would be very expensive. We have normally used small pads to reduce cost. There are a few other similar materials which have a special composition of intergranular lubricants in a hard matrix (PTFE in Bronze, bronze in stellite etc.) If you can´t find any suppliers I can look through my old papers if you feel this route is worth pursuing.

Good Luck!