I can use any two of the list below for a medium-duty sliding bearing in an
agressive oxygen environment (3,000 psi and ~200C).

Keeping cost and availability in mind, which would be the best pair to use
both as a low-friction bearing and to avoid galling (the cheapest and most
available pair which would work reliably would probably be the best choice)?

Imagine a 6 mm shaft in a plain unlubricated bearing, under light-to-medium
load and low speed.


I don't know much about choosing metals, there may be an obvious choice or
two in there, and if such exists that's what I'd like to know - please don't
omit the simple answers, I am a newbie at this!

Quantities involved are small, so availability of small quantities at
reasonable rates is more important than raw cast.


Brass (any)
Tin Bronze (but not Aluminium Bronze)
Nickel 200
Copper 102
Beryllium Copper
Monel 400
Monel K-500
Silver
Inconel
MA-754
Haynes 188
Haynes 242

This selection is from the G4/NASA/ASTM manual 36 - I haven't heard of some
of them before.

Some ceramics would be okay chemically too, for instance Alumina, Silica and
Zirconia would be, and probably Macor, but I don't know if they would be
strong enough. I know very little about engineering ceramics, any help would
be appreciated.



Thanks,


--
Peter Fairbrother

"Peter Fairbrother" wrote in message
...
I can use any two of the list below for a medium-duty sliding bearing in
an
agressive oxygen environment (3,000 psi and ~200C).

Keeping cost and availability in mind, which would be the best pair to use
both as a low-friction bearing and to avoid galling (the cheapest and most
available pair which would work reliably would probably be the best
choice)?

Imagine a 6 mm shaft in a plain unlubricated bearing, under
light-to-medium
load and low speed.


I don't know much about choosing metals, there may be an obvious choice or
two in there, and if such exists that's what I'd like to know - please
don't
omit the simple answers, I am a newbie at this!

Quantities involved are small, so availability of small quantities at
reasonable rates is more important than raw cast.


Brass (any)
Tin Bronze (but not Aluminium Bronze)
Nickel 200
Copper 102
Beryllium Copper
Monel 400
Monel K-500
Silver
Inconel
MA-754
Haynes 188
Haynes 242

This selection is from the G4/NASA/ASTM manual 36 - I haven't heard of
some
of them before.

Some ceramics would be okay chemically too, for instance Alumina, Silica
and
Zirconia would be, and probably Macor, but I don't know if they would be
strong enough. I know very little about engineering ceramics, any help
would
be appreciated.



Thanks,


--
Peter Fairbrother



Unless you get lucky and someone here happens to know how materials behave
in that extreme oxidizing environment, I think you're going to have to talk
to a professor of materials science at some university.

I hope you find an expert here but I think you're going to have to find a
specialist. Whenever I've had to deal with tough materials questions in the
past I've gone to one or two university profs at places like Ohio State or
Purdue, who usually know who the expert is. Sometimes I used to start with
the ASM. Then I track down the expert they send me to.

Other things you might try are, first, Google's new Scholar function.
Obscure engineering papers sometimes show up there. The other one, if I were
going to a commercial source, would be Balzers, who make ceramic coatings
for demanding applications as well as for cutting tools; finally, I'd try
someone who supplies Haynes 25 and other Haynes alloys for technical
applications.

Good luck. My guess is that an oxide- or nitride-type ceramic is a likely
candidate (silicon nitride, IIRC, is used in high-pressure oxygen
environments, but I don't know how it works out as a bearing surface), but
that's only a guess. If any of the metals can tolerate it, it probably would
be one of the superalloys, like Haynes or Inconel.

--
Ed Huntress

Ed Huntress wrote:

"Peter Fairbrother" wrote
I can use any two of the list below for a medium-duty sliding bearing in
an agressive oxygen environment (3,000 psi and ~200C).

Keeping cost and availability in mind, which would be the best pair to use
both as a low-friction bearing and to avoid galling (the cheapest and most
available pair which would work reliably would probably be the best
choice)?
Imagine a 6 mm shaft in a plain unlubricated bearing, under
light-to-medium load and low speed.

[...]
Brass (any)
Tin Bronze (but not Aluminium Bronze)
Nickel 200
Copper 102
Beryllium Copper
Monel 400
Monel K-500
Silver
Inconel
MA-754
Haynes 188
Haynes 242

This selection is from the G4/NASA/ASTM manual 36 - I haven't heard of
some of them before.

Some ceramics would be okay chemically too, for instance Alumina, Silica
and Zirconia would certainly be, and probably Macor too, but I don't know if
they would be strong enough. I know very little about engineering ceramics,
any help would be appreciated.

Unless you get lucky and someone here happens to know how materials behave
in that extreme oxidizing environment, I think you're going to have to talk
to a professor of materials science at some university.

You miss the point. I have already done the oxygen-compatibility research
(or G4/NASA/ASTM did it for me), with the possible exception of the oxygen
suitability of Macor which needs an emails' more investigation by me.

I have lots of paper on that, including friction ignition test data, but I
want to use materials which will not sustain (rather that initiate)
combustion in this particular part of the system, and the materials in the
lists above are the only suitable ones I know of.





What I want to know is is a pair of materials from the above lists, one of
which will form a strong and tough (but not outrageously-so, about like mild
steel) 6mm shaft, and the other will form an unlubricated bearing, with the
pair not galling. That's all.






NASA lists Copper Beryllium / Monel 400 as the best pair overall for
instance, which would be doable, but any pair would do, and really I am
looking for the cheapest and least-galling shaft partner for a leaded
tin-bronze bearing, which would be readily available - Monel K-500 would do
as a shaft, it is hard and just-about-dissimilar enough, but is there a
cheaper and more available choice, from the lists given?


Or does anyone know where to get a foot or two of 6 mm Monel K-500 rod,
not-to-expensive?? I've never come across it before. I think it has to be
hardened somehow too. Centreless ground accuracy would be really nice ...




No expertise on oxygen-compatibility of materials is sought however,
although it would be very much appreciated if available. I shall look into
your suggestions about that, thanks.




A note about compatibility:

Designing for oxygen service is a bit of a black art, but the basic
principles are either (or all three!):

1) avoid sources of ignition - sounds a bit iffy, but often you have little
choice, as almost _everything_ will react with high-pressure oxygen,
especially when hot, even teflon will burn

2) use some of the very few materials, like oxide ceramics -
sapphire/alumina/silica/zirconia (but not silicon nitride, which burns) that
won't react,

3) use materials that won't sustain combustion in the sizes and shapes
involved.



It's not really possible to reliably avoid ignition sources in my
application, I don't know of suitable unreactive materials - any ceramic
experts here? - so I have to go with the last option, materials that will
not sustain combustion.


If galling occurs then fresh surfaces will be exposed and/or small particles
will be produced, and the material will likely ignite and the parts will
likely be ruined, as will some downstream parts; but the materials on the
lists won't sustain combustion in these shapes, even if they ignite, and if
the parts are made from them the flame will go out, and the overall fire
will be containable.




Thanks,


--
Peter Fairbrother

In article ,
says...
Ed Huntress wrote:



Unless you get lucky and someone here happens to know how materials behave
in that extreme oxidizing environment, I think you're going to have to talk
to a professor of materials science at some university.

You miss the point. I have already done the oxygen-compatibility research
(or G4/NASA/ASTM did it for me), with the possible exception of the oxygen
suitability of Macor which needs an emails' more investigation by me.

I think you've missed Ed's point. Picking a pair of materials that
perform together well in a normal atmosphere at a given temp will not
insure that they'll give acceptable performance in a strongly oxidizing
environment. I've got some experience at the other end of the spectrum -
hydrogen atmospheres at high temperatures - and can tell you that the
behavior of bearing materials in air is not a good predictor of their
performance in a reducing atmosphere. I'd expect the same to be true for
extrapolating from air to oxidizing environments.

Ned Simmons

"Peter Fairbrother" wrote in message
...
Ed Huntress wrote:

"Peter Fairbrother" wrote
I can use any two of the list below for a medium-duty sliding bearing
in
an agressive oxygen environment (3,000 psi and ~200C).

Keeping cost and availability in mind, which would be the best pair to
use
both as a low-friction bearing and to avoid galling (the cheapest and
most
available pair which would work reliably would probably be the best
choice)?
Imagine a 6 mm shaft in a plain unlubricated bearing, under
light-to-medium load and low speed.

[...]
Brass (any)
Tin Bronze (but not Aluminium Bronze)
Nickel 200
Copper 102
Beryllium Copper
Monel 400
Monel K-500
Silver
Inconel
MA-754
Haynes 188
Haynes 242

This selection is from the G4/NASA/ASTM manual 36 - I haven't heard of
some of them before.

Some ceramics would be okay chemically too, for instance Alumina,
Silica
and Zirconia would certainly be, and probably Macor too, but I don't
know if
they would be strong enough. I know very little about engineering
ceramics,
any help would be appreciated.

Unless you get lucky and someone here happens to know how materials
behave
in that extreme oxidizing environment, I think you're going to have to
talk
to a professor of materials science at some university.

You miss the point. I have already done the oxygen-compatibility research
(or G4/NASA/ASTM did it for me), with the possible exception of the oxygen
suitability of Macor which needs an emails' more investigation by me.

I have lots of paper on that, including friction ignition test data, but I
want to use materials which will not sustain (rather that initiate)
combustion in this particular part of the system, and the materials in the
lists above are the only suitable ones I know of.


Good luck, it sounds like a challenge.

--
Ed Huntress

"Ned Simmons" wrote in message
...
I've got some experience at the other end of the spectrum -
hydrogen atmospheres at high temperatures - and can tell you that the
behavior of bearing materials in air is not a good predictor of their
performance in a reducing atmosphere.

Yeah, but high temperatures tend to make things stick together (diffusion
for instance) while the hydrogen fluxes any oxides. Heck, again on the
opposite side of things, the bearings may even work better!

Tim

--
"California is the breakfast state: fruits, nuts and flakes."
Website: http://webpages.charter.net/dawill/tmoranwms

In article , says...
"Ned Simmons" wrote in message
...
I've got some experience at the other end of the spectrum -
hydrogen atmospheres at high temperatures - and can tell you that the
behavior of bearing materials in air is not a good predictor of their
performance in a reducing atmosphere.

Yeah, but high temperatures tend to make things stick together (diffusion
for instance) while the hydrogen fluxes any oxides. Heck, again on the
opposite side of things, the bearings may even work better!


Better in hydrogen or oxygen? You're right about the reducing atmosphere
stripping the surface of metals. This, combined with the heat, makes
metals in close contact prone to seizing.

Ned Simmons

From: "Ed Huntress"
...I've gone to one or two university profs at places like Ohio State or
Purdue...

Forget OSU!

Randy
http://www.chem.purdue.edu/machine

"Randy Replogle" wrote in message
news:wSGWd.80123$wc.78806@trnddc07...

From: "Ed Huntress"
..I've gone to one or two university profs at places like Ohio State or
Purdue...

Forget OSU!

Ohio State has become a refuge for Indian postgrads in manufacturing
engineering and related fields. They're very good.

Purdue has a longer tradition of research in the field, and there are a
several cow colleges, including my alma mater, Michigan State, where you'll
find some really good people.

--
Ed Huntress

Seriously look up the Steel number - 8620. It is a sliding, non-galling metal.
Used as a base metal and slide metal of the M14 as an example.

Martin

Ed Huntress wrote:

"Randy Replogle" wrote in message
news:wSGWd.80123$wc.78806@trnddc07...

From: "Ed Huntress"
..I've gone to one or two university profs at places like Ohio State or
Purdue...

Forget OSU!


Ohio State has become a refuge for Indian postgrads in manufacturing
engineering and related fields. They're very good.

Purdue has a longer tradition of research in the field, and there are a
several cow colleges, including my alma mater, Michigan State, where you'll
find some really good people.

--
Ed Huntress




--
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder

"Martin H. Eastburn" wrote in message
m...

Seriously look up the Steel number - 8620. It is a sliding, non-galling
metal.
Used as a base metal and slide metal of the M14 as an example.

Martin

If this is running in oxygen then 8620 would be a baad choice. Carbon steels
are dodgy in oxygen. (Yes I know medium pressure oxygen tanks and pipelines
are made in carbon steel).

I would consider inconel / tin bronze.






"Randy Replogle" wrote in message
news:wSGWd.80123$wc.78806@trnddc07...

From: "Ed Huntress"
..I've gone to one or two university profs at places like Ohio State or
Purdue...

Forget OSU!


Ohio State has become a refuge for Indian postgrads in manufacturing
engineering and related fields. They're very good.

Purdue has a longer tradition of research in the field, and there are a
several cow colleges, including my alma mater, Michigan State, where
you'll
find some really good people.

--
Ed Huntress




--
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder