What is Powder Metallurgy?

Larrin

Larrin

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In this article I describe the process of powder metallurgy including:

How does powder metallurgy refine the microstructure of steel?
When was powder metallurgy invented and which company was the first to use it?
What were the early steels used with powder metallurgy and how were steels developed differently to take advantage of the technology?

https://knifesteelnerds.com/2018/08/20/what-is-powder-metallurgy/
 
Making the powder is essentially shot casting? Hah, neat. How do they control the granule size? Is it just a matter of flow:atomization?
 
kuraki said:
Making the powder is essentially shot casting? Hah, neat. How do they control the granule size? Is it just a matter of flow:atomization?
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The logistics of powder metallurgy (flow, gas stream, etc) are outside of my knowledge area. To some extent the powder size is controlled with with a sieve. It depends on what the company finds acceptable in terms of powder size.
 
Cool. Two questions.
1. So is the fact that AEB-L, 13C26 et al are right near that 10% line what causes it to have those small secondary carbides and fine grain structure or is it a combination of low chromium and relatively low carbon content? The behavior of D2 would cause me to think that it is the latter, but I figured that I would ask anyway.
2. What are the "mechanical" differences, if any, between the HIP, "forge welding" and sintering processes?
 
jdm61 said:
Cool. Two questions.
1. So is the fact that AEB-L, 13C26 et al are right near that 10% line what causes it to have those small secondary carbides and fine grain structure or is it a combination of low chromium and relatively low carbon content? The behavior of D2 would cause me to think that it is the latter, but I figured that I would ask anyway.
2. What are the "mechanical" differences, if any, between the HIP, "forge welding" and sintering processes?
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1. It is the composition (carbon-chromium combination) plus excellent processing by Sandvik or Uddeholm that gives it the very fine carbide size.
2. I'm not 100% sure what you mean by mechanical differences. One distinction I can help with is that HIP is a sintering process, so those are not so much different as HIP is a more specific version of sintering.
 
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That is what I thought re HIP vs. sintering.
Larrin said:
1. It is the composition (carbon-chromium combination) plus excellent processing by Sandvik or Uddeholm that gives it the very fine carbide size.
2. I'm not 100% sure what you mean by mechanical differences. One distinction I can help with is that HIP is a sintering process, so those are so much different as HIP is a more specific version of sintering.
Click to expand...
 
Good write-up.

I liked the Bohler Uddeholm video. It is really nice to hear their name pronounced properly with an umlaut .... "Buulah" not "Bowler". :thumbsup::thumbsup::)
 
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Stacy E. Apelt - Bladesmith said:
Good write-up.

I liked the Bohler Uddeholm video. It is really nice to hear their name pronounced properly with an umlaut .... "Buulah" not "Bowler". :thumbsup::thumbsup::)
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I was talking to an Austrian metallurgist who works for the parent company Voestalpine and she had no idea what I was talking about with my pronunciation of Bohler. Until I spent 3 minutes explaining which company I was talking about and then she pronounced it correctly. :)
 
kuraki said:
Man. If this really gets out my business is gonna suffer. "3V is MiM junk!" :eek:
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That would require a pretty significant misunderstanding of the two processes. Though there have been things that are more dissimilar that people have confused.
 
kuraki said:
Making the powder is essentially shot casting? Hah, neat. How do they control the granule size? Is it just a matter of flow:atomization?
Click to expand...
seems each company has a "proprietary" process, some use vacuum, some inert gas, some both. granule size is by sifting once it is done.
 
great read and glad to know "first gen vs 3rd gen" is all about screen size not as much tec. was cool seeing Carpenter and the newly bought timkin plants worked when i got the foundry tours
 
I am not a very smart guy, but the explanation doesnt make sense to me. The carbides get large and stable when the steel is in liquid form, and then rapid cooling produces smaller dendrites which indicates less segregation (paraphrasing from the article). So i guess this means rapid cooling busts up the carbides? I would expect a near instant solidification to lock the carbides in place. If a granule size after atomization is one the order of a few um, then i can see the carbides fracturing into smaller chunks, each of which is a "granule". If the granule size after atomization is on the order of a few 10um, then i just dont understand how the process works.
 
The carbides don’t form until atomization. The temperature is too high prior to that for the carbides to form in the liquid.
 
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