4340 -- elevated temp properties vs 17-4?

[phonix]

I am making a part which needs to maintain as much yield strength as possible in the 1000 to 1500 degree F range when subject to pressure. The part failed when made out of 4140. It did not fail when made from Inconel-718 -- but that was expensive. We are beefing up the part which will help.

I need a lower cost material and am thinking of 17-4 PH, 4340, 300m, 286A, Greek Ascoloy, or Nitronic 50/60. Any ideas what as the most yield strength at 1100, 1200, and 1500 degrees? It would be subject to these temps just for a few minutes on a few occasions but otherwise will generally be below 600 degrees F.

I understand that materials which rely on their heat-treatment for strength give that up as they approach the temp they were treated at.

 

[israelkk]

If 1500F is possible then 1500F is what matters. If 4140 failed and assuming it was heat treated then it was probably normalized during those "few minutes".

 

[metengr]

phonix;
You need to narrow your design conditions for your component. What is the pressure you are using for your application? What are the contents under pressure? Is this a pressure vessel?

Here is some general advice; you should use 1500 deg F as the maximum service temperature (regardless of time duration or frequency), along with defining a maximum allowable working pressure. Once you have these parameters established, you can search through various Ni-base alloys or austenitic stainless steels (Type 304,304H, 316,316H) as suitable materials.

IF this is a pressure vessel, I would use the ASME Boiler and Pressure Vessel Code for design and seek technical expertise.

 

[phonix]

Thanks.

But does anyone know the 0.2% yield strength at 1500 degrees for each material or at least for 4140, 4340, and 17-4? Won't that give some quick insight?

I am not sure that 1500 F numbers are published for each material since it is above the design use for some of them.

 

[metengr]

The three materials you mention above are not suitable for use at 1500 deg F. Both 4130 and 4340 have a significant loss in yield strength and ultimate tensile strength properties because of solid state phase changes slightly below 1500 deg F that render the material unsuitable for pressure containing applications. Also, depending on the environment, the 4140 and 4340 steels will suffer rapid oxidation (loss of material) at 1500 deg F.

The 17-4PH material has unpredictable properties above 600 deg F. Does this answer your question? Also, if you are going to use these materials in a pressure containing application, I can tell you with certainty that none of these materials are permitted at 1500 deg F.

 

[arunmrao]

Continuing with metengr's explanation you would be best advised to use a steel which does not undergo phase transformation ar elevated temperature. also there should not be significant grain growth and oxidation at high temperatures. You will be well advised to explore the possibilities of high temperature austenitic stainless steels.

 

[phonix]

It is not a pressure containing application. It is subject to pressure but it is not contained. It is a flash hider for a rifle.

I know none of them are suitable for 1500 degrees. In my original post I said 1000-1500 and asked which was strongest at high temps. I want to know which moderate cost material would likely last the longest at high temps. In no way am I asking for a 1500 degree rating.

 

[metengr]

phonix;
Use 304 or 316 stainless steel.

 

[phonix]

I thought of 304 and 316. I forgot to say one other requirement -- it has a ratchet-tooth on the back of it. That part will not get red hot ever, but it needs to be hard enough to not wear easily. So 304, 316, and Nitronic 50/60 are ok but not great in that regard since they are Rockwell C30 or so.

I am excited about 418. What do you all think?

http://www.hightempmetals.com/techdata/hitemp418data.php

It is still about 60KSI yield at 1100 degrees F -- that is twice as strong as 316 at room temp. It is hardenable. It machines ok in annealed form. Seems like the best overall solution. Agree or disagree?

 

[arunmrao]

Martensitic stainless steels too suffer loss of properties at elevated temperatures desired by you. This is substantiated in your 418 data sheet too.

 

[phonix]

Interesting.

The 1200 degree, 1000 hour stress rupture for 316 is 24KSI.

For 418 it is 11KSI.

http://www.hightempmetals.com/techdata/hitemp418data.php

http://www.alleghenyludlum.com/ludlum/documents/316 (060906).pdf

(page 10).

So if I went by this, 316 would be superior. However, 316 is Rockwell C-zero basically. That is not very good for our exposed ratchet teeth. I think I need the hardness of the 418, and just have to live with the high-temp limit of around 1100 degrees.

 

[arunmrao]

consider to nitride the exposed ratchet teeth made of 316 material.

 

[TVP]

phonix,

As arunmrao mentioned, surface hardening of Type 316 can be done using the nitriding process. This will improve the wear resistance, and if it is one of the newer processes, will not degrade the corrosion resistance. Use the following link for more information:

http://www.kolsterising.bodycote.com/

 

[EdStainless]

Can the part be investment cast? There are a lot of Ni based superalloys that will give you 100ksi yield at 1500F. All but a few are strictly cast grades. If you want wrought material then alloys like 725, 718 or 214 are about your only choices.
I don't know of any Fe based alloys that have significant strength at 1500F.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm