Why Powder Metalurgy?

A

Atemporal

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Aug 4, 2012
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What is it about steels like CPM 3V that requires them to be powder formed, as opposed to milled or forged? Is the alloy too strong to work with, or is it brittle at high temperatures? Prone to decarburization? I have never heard of anybody forging this steel and I assume there must be a good reason for it.
 
When you start with powdered ingredients, you have a much better end result steel. Steel which has a better distribution of carbides and such. Produces a higher grade steel than having the conventional mix.
John
 
As John said, the distribution of the components within the steel is better. I've used conventionally made steels where different sections of the blade oxidized while others didn't, these different zones will mean a blade with varying edge holding abilities and also have zones where it's more likely to be weaker. The more thorough mix that powdering the steel prior to sintering results in will avoid these pitfalls. I believe it also minimizes grain growth within the steel that comes with slower cooling times, conventional billets can take days to cool where smaller formed bars cool faster and exhibit the finer grain which is better for blades.

I don't know of any steels that "have" to be powder formed, it's simply beneficial to do so. For example, the powder version of ATS-34, namely RWL-34 is a very notable improvement. It's a great steel either way, it's just better when it starts life as a powder.

As far as not forging them, there I can't help, I'm a stock-removal maker, hopefully a hammer-wielder will weigh in.
Gazza
 
Smaller particles?
That said IMHO, the most underated steel is CPM D2.
I only have 1 example and I recently dressed 2 deer, VERY, VERY IMPRESSED!
Still shave every hair on you arm after those two!
 
Mod 7 said:
Smaller particles?
That said IMHO, the most underated steel is CPM D2.
I only have 1 example and I recently dressed 2 deer, VERY, VERY IMPRESSED!
Still shave every hair on you arm after those two!
Click to expand...

I'll second that on the CPM-D2, it is a great steel.
 
As others have said, it creates a more uniform steel. I don't think it is possible to hammer out a large section of steel from the powder by hand, as production uses very high heat and pressure.

Connor
 
I should comment here - The original term " Powder Metal " was a process where metal powder was compressed in a precision die ,and sintered to bond the particles .You can adjust the density to make anything from filters to prelubricated bearings to close to wrought properties through a double compress an sinter operation .It's still being used . It's the prediciser to MIM [metal ,injection molding ]. But that name has been almost totally replaced by it's use in tool steels and knives.
Today's PM includes the early Crucible Particle Metallurgy and other types found on Europe.
More homogenous, tougher [especially transverse], finer carbide size. Don't confuse carbide size and grain size !! Carbide size comes from the original making of the steel but grain size is determined by HT. The PM methods give us easy to sharpen .stays sharp longer. Ability to easily make alloys that otherwise would be difficult.

Atemporal , it's spelled metallurgy ! High tech, high alloy steel aren't often forged mostly because they are tough .
A good test to see the difference between standard and PM is to make two knives,identical except one in 154CM and the other CPM154.You'll see the difference .
 
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