higher than "super alloy" but lower than "refractory"

[robertsolo]

Looking for a metal that can live in a  Aluminium fluoride (AlF3) vapor > 1,290 °C (2,350 °F; 1,560 K) environment , have elongation > 5% better >8% . yield ideally >125,000 Psi. , lifetime > 85 hours . looking for something that will get the job done without "overkill".

[John Cuthber]

Tungsten might still have that much strength at that temperature.

Not many things are that strong, even at 20C.

What are you seeking to achieve?

[robertsolo]

I am sorry I thought I used all the common temperature scales but you seem to have a uncommon scale , very uncommon , why ? As to your Question I feel I have answered it.

[John Cuthber]

There is nothing uncommon about centigrade, apologies if missing out the degree sign confused you.

20C is a typical room temperature (at least in my country)

Not many things have yield strengths of 125,000 PSI or 125 KSI or 860MPa , even at room temperature

https://en.wikipedia.org/wiki/Ultimate_tensile_strength#Typical_tensile_strengths

 

and things generally get weaker when they get hot.

 

 

[robertsolo]

Your kidding 125, 000 is not very high , there are hundreds  of alloys/heat treats that exceed 125,000 PSI yield ,  I use alloys that exceed 220,000 Psi yield every day , and they been common since the 1950's , 2100F-2200F is very easy using off the shelf tubing , I am assuming a powder metallurgy alloy of some sort would be all that is required to raise the temperature  200F  , not "off the shelf" but something that could be custom made if I find a facility with the right experience and no other jobs at the moment . I would guess yield at temperature of > 40,000  is within easy reach and 125,000 is a not unreasonable goal to shoot for. 

[John Cuthber]

6 minutes ago, robertsolo said:

here are hundreds  of alloys/heat treats that exceed 125,000 PSI yield

How many of them are not "steel"?

 

[robertsolo]

mind defining "steel" ? and that was not a requirement any way ,

[Bender]

Elongation of 8%?

I know of only one metal that can do that: the superelastic nitinol, a shape memory alloy. Its yields strength is below your requirement and, since it is an alloy, its melting point will be very near to your 1500K.

Perhaps other, less common, superelastic alloys are stronger, but I doubt they'll meet your specs. Even these superelastics have pretty short lifetimes at 8% elongation at room temperature.

Lifetime is usually not expressed in hours, but in number of cycles (unless perhaps the AlF is the bottleneck, but it doesn't even need to be considered to decide that what you want doesn't exist).

Edited April 21, 2018 by Bender

[robertsolo]

8% that is nothing , lots of alloys/heat treats have elongations of 40% or more that is very common . Sorry I did forget to mention 85 hours of 10 minute " hot cycles" then cooling to room temp 20C  

[John Cuthber]

44 minutes ago, robertsolo said:

mind defining "steel" ? and that was not a requirement any way ,

Mainly iron.

Nobody said it was a requirement.

Edited April 21, 2018 by John Cuthber

[Bender]

2 hours ago, robertsolo said:

8% that is nothing , lots of alloys/heat treats have elongations of 40% or more that is very common . Sorry I did forget to mention 85 hours of 10 minute " hot cycles" then cooling to room temp 20C  

Is this some kind of weird imperial unit thing, or are you planning plastic deformation?

I wouldn't call it common to stretch a 1 meter metal bar to 1,4m length.

[StringJunky]

13 minutes ago, Bender said:

Is this some kind of weird imperial unit thing, or are you planning plastic deformation?

I wouldn't call it common to stretch a 1 meter metal bar to 1,4m length.

Any increase of length of metal, besides from thermal expansion, is plastic deformation, isn't it. Would be a lot easier if he just said what he was doing instead of playing 'Twenty questions'.

Edited April 21, 2018 by StringJunky

[studiot]

21 minutes ago, StringJunky said:

Would be a lot easier if he just said what he was doing instead of playing 'Twenty questions'.

Unless that purpose was less than straightforward.  +1

[Bender]

9 hours ago, StringJunky said:

Any increase of length of metal, besides from thermal expansion, is plastic deformation, isn't it. Would be a lot easier if he just said what he was doing instead of playing 'Twenty questions'.

It would be much easier indeed. (Metric units would be as well :))

But before plastic deformation, there is elastic deformation. For high strength steel that can be as high as 1% (yields stress of 2000MPa / Young's modulus of 200GPa), and for nitinol up to 8% (with very nonlinear stretch curve).

[John Cuthber]

Guys, I may be mistaken, but I think there's a post limit of something like  5 a day for newbies and so he's not well placed to answer these questions yet.

Give him a chance and we may yet see what he's hoping to do, what units we like and whether or not all his array of "hundreds  of alloys/heat treats that exceed 125,000 PSI yield" are actually all variations on a thing called steel.

[robertsolo]

Yes yield is plastic deformation , before that you have elastic deformation , elongation happens after yield and before failure , In "critical" structures one tries ( but does not always succeed ) to have 10 % elongation in order to have a "tough" structure that bends ( hopefully away from the load , lessening it ) some , before failure . I am not trying to play "twenty questions" I work for a company in a competitive business . If you define "steel" as having 50% iron (not a accurate definition , you need to limit the carbon , or you will include cast irons )  then a lot of alloys I mentioned are steels but plenty are not and most of the high temperature alloys are not in high temperature alloys iron is used to reduce mix cost and provide sigma phase control . but what I am looking for is 200C beyond my experience with "common of the shelf " but 200C is just too close to not be possible today , especially with my willingness to make it a replaceable part with a limited lifetime.  

[Bender]

The only advice I can offer is point to CES material selection software, which has a huge material database.

[robertsolo]

I am not proud of this but I read a paper  ( a while ago ) written by a competitor (German)  and they did not say ANYTHING specific , but they could not help but drop a few clues , and it just "clicked" , what the "Germans" are doing they are using a high temperature alloy probably  similar to HAYNES® 214® alloy (UNS N07214)  a nickel - chromium-aluminum-iron alloy, witch is off the shelf  and way cheaper then some of the solutions I was thinking about and bonding a layer of graphite over it  ( Graphite is good around fluorine and somewhat insulates the alloy armature and it is dirt cheap ! ) . They thought outside the box if you cannot find one material to do the job , try two ! I got to hand it to the Germans they got some good engineers , they made me feel like a amature , I am sure we will be copying them .

Thanks guys 

[John Cuthber]

Do you mean this stuff?

http://haynesintl.com/docs/default-source/pdfs/new-alloy-brochures/high-temperature-alloys/brochures/214-brochure.pdf?sfvrsn=8

Because, as far as I can tell, it doesn't meet the criteria you specified of 125KSI at anywhere like 1290 C. It falls below 125KSI at some temperature below 600C

It doesn't seem to have any reported properties above 1204C

And your specification is with 100C of the melting range (1355-1400C).

 

Wrapping it in graphite might be interesting.

 

[studiot]

I remember doing a material failure investigation on a german super alloy (steel).

 

The emergency repair on the bridge bearing cost £1/4 million,  leaving 63 more bearings at risk on the viaduct.

[robertsolo]

The company only gives properties up to 50% reduction that is very mild , on the Atlas program every time the ends did not meet they just specified a greater reduction , also just making a educated guess I would bet that the graphite lowers the temperature at least 700 F ( I can't make educated guesses in metric , I'm old school) and 900F does not sound unreasonable , also who knows what they are using . and even with 50% reduction you get 100,000 yield at 1700F and 33% elongation (at temperature)  now raise the reduction you will increase yield and reduce elongation ( and you have some to spare there ) ... easy pesy , but I got to give credit where credit is due .  It would be a smidge  fragile when it was cold  but still  tougher than carbon carbon ( the 24 carrot gold solution , but getting cheaper ) 

Not wrapping it , lining it.

[Bender]

18 hours ago, robertsolo said:

also just making a educated guess I would bet that the graphite lowers the temperature at least 700 F

Graphite is a (much) better heat conductor than your material, so it would have to be a pretty thick layer to insulate the material against the heat.

Perhaps you could look at what they use to line steel ladles.  

[John Cuthber]

18 hours ago, robertsolo said:

The company only gives properties up to 50% reduction that is very mild

Which company?

Reduction of what?

The page I cited showed reductions of strength of the order of 50 fold

18 hours ago, robertsolo said:

Not wrapping it , lining it.

Still going to be interesting given the difference in expansion coefficients.Also potentially interesting if the carbon migrates into the metal.

[robertsolo]

Haynes International , reduction of the metal thickness when you cold roll most metal you will strengthen it that is how  music  wire ( drawn  up to 440,000 PSI tensile ) and razor blades ( 500,000 -600,000 PSI Tensile  ) are hardened . You were looking at the dead soft annealed numbers , look at the " Effect of Cold Reduction upon Room-Temperature Tensile Properties*" in the Haynes brochure  and extrapolate from there , also razor blades have almost no elongation but are tougher than carbon fiber (low modulus ) with 4 % so there is more to it , or at least the rules don't seem to hold at very low elongations , any one got any theories ?

[John Cuthber]

1 minute ago, robertsolo said:

You were looking at the dead soft annealed numbers

Did it occur to you that I may have been doing that because you specified

> 1,290 °C (2,350 °F; 1,560 K) environment

?