Powder Metallurgy (PM)Problems

[boshwhere]

Hi,

I am working on PM produced basic 12 Cr steels, and facing many problems related to mechanical properties.

one of the problems is there are many intermetallic particles and some of them are quite big around 2 micron in size. and in facture surfaces after tensile tests there are thousands of them can be visible. those particles effecting in a negative way i think. causing secondary particles related void formation or wetting problems etc. what do you think ?

and the other problem is elongation two very close composition samples both has some dispersions but different sized, the only difference is size of dispersions one with 0.9 micrn the other one with 50nm. smaller sized one showing very small elongation around %6 while the other one is around %12 even small but good when compared to the first one. what can be the reason do you think ?? theoretically small particle one performs better elongation and better mechanical properties but there is something wrong in this case. distribution might be the reason but how ?

Regards

 

[cloa]

How are you doing the powder metallurgy?

http://www.mpif.org/IntroPM/process.asp?linkid=2

To achieve what percentage density?

 

[EdStainless]

What are the intermeallics? Nitrides, oxides, carbonitrides?
Is there any Al or Ti in the alloy?

Sounds like either you powder is 'dirty' or your sinter/anneal cycle isn't reaching the correct time/temp/cleanliness.

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Plymouth Tube

 

[boshwhere]

it is hot isostatic pressed without any secondary processing after that, heat treatment at 650C for 2 hrs after oil quenching

intermetallics are some oxides and some sulfides i think, i did just EDX and showing mainly Mn-S and Si-0 , neither Ti and Al in the alloy.