Cold working/peening powdered/sintered metal blades?

[kayakingsteve]

Sorry if this question has been asked and answered a thousand times, but I can't seem to find an answer anywhere:

Can you peen/thin a sintered blade edge face? I know this would depend on a lot of things, like hardness and alloy in general?

I'm used to doing a little peening and cold working of scythe blades but have no idea the hardnesses and physics involved with sintered metal in production knives now? My instinct is telling me sintered metal wouldn't have true ductility since it's actually a compressed/porous structure (please don't yell at me, this is my rudimentary understanding)

any good guides out there? answers?

 

[mete]

"sintered" means heating to bond particles together. Proper words have changed definitions . If you are talking about modern powder metal blades you actually have a homogenous material .The earlier definitions is a collection of particles and the amount of bonding between the particles can vary a large amount ! The less the bonding the more brittle the material. A double sinter + pressing operation will gives a structure very close to wrought material and that could be peened easily. The lesser bonded types would break before much peening occurred !
Modern "powder metal " like the CPM types can be peened but the process may not give you properties you want. Your scythe might be .40 % carbon and like the earlier bronze swords were often peened on the edges to thin ["sharpen" ] and harden the edge ! Reduction of area was about 10% max. Modern sintered steels get their hardness through alloying and HT !
Changing definitions certainly annoys me , having done considerable work with the original PM !

 

[kayakingsteve]

"sintered" means heating to bond particles together. Proper words have changed definitions . If you are talking about modern powder metal blades you actually have a homogenous material .The earlier definitions is a
... ... Changing definitions certainly annoys me , having done considerable work with the original PM !

Thanks for the reply! I'm a bit confused by the changing techniques and and terminology. I am wary of any of the powdered metal based blades but am probably just being a Luddite. I'm most worried about toughness and the ability of a blade to take abuse. I can deal with less corrosion resistance and less edge holding in exchange for knowing it will not be too brittle. Any good torture-test comparisons of powdered metal knives versus traditional alloys?

Thanks and sorry for any mis-use of neo-terminology.

 

[mete]

Modern PM steels are inherently tougher ,especially in the transverse direction ! Easy to sharpen, holds it's edge better and that's why the higher price.

 

[chiral.grolim]

Like mete said, you shouldn't need to peen a PM blade, then again a scythe in PM steel would be a surprise and probably very expensive! Typical scythe blades these days are 1080 steel or the like (basic 0.8% carbon with almost no carbide content) and tempered back to 47 Rc.

Part of the joy of PM steels is that they allow for a much higher carbide fraction or at least higher vanadium content to improve abrasive wear resistance without compromising toughness (as would be the case with ingot steels). These processes would not be of much value in 1080 steel and such low hardness.