Carbon diffusion in ss laminated blade

SBranson

SBranson

Joined
Oct 29, 2006
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This is my second try at a laminated blade. The first was 416ss and 52100 and didn't have the problems this one is having.

This attempt was 416ss and 1084. The choice was of convenience as had the 1084 in bar stock.. All pieces were 1/8" to start and I forged it down to a little under 1/8".

I HT'ed it and went to grind it and the tip was very soft. I started checking and it very soft at the tip and intermittent along the edge so a quick etch revealed this:

failedkitchenknife_01_zps9728ca89.jpg


So, did the 416 rob the 1084 of carbon or something? Something to do with forging at such high heat?

I'm not sure what's going on here. I thought it might be near the edge and ground the profile down but that didn't help.

Sucks to lose a piece of 416 like that. It's pricey stuff up here.
 
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That may be part of it, plus you may have forged it down too thin and the core is meandering back and forth. I would have thought a thicker core would be a better idea.
One of the stainless clad guys will probably pop in soon.
 
Thanks. I don't think it was a meandering core as I was quite careful and several times ground the edge lightly and did a quick etch to see that it was straight and centered. Plus you can see where the lamination line it. To me the mystery is the blotchiness in the 1084 layer.

To make a kitchen knife then how would you go about this? You want a thin blade..
Is the only option nickel to separate the layers? Or would starting with a steel with a higher carbon content help?
 
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When laminating stainless I have better, more consistent results when I start with thicker stock. I use 1/4" for both steels and I seem to get less of a carbon migration line then when I used thinner stock. I also try to weld at the lowest temp possible.
 
15N20.. good idea... Thanks.

My problem I think might still remain as trying to get down to 1/8" or less for a kitchen knife might be pushing it. Maybe the way I'm doing it with thin nickel sheet?

I ended up grinding this one down to more of a petty size and it will still work..
 
There's some nickel sheet on ebay and I wonder if foil would work or go with something like 0.020" sheet?
 
I have never forge welded anything, so I have no first hand experience. Newbie question: Won't the carbon migrate through the 15N20 anyway? The nickel won't migrate, but the carbon should. Secondly, with such thin stock, could part of the problem be decarb?
 
SBranson said:
15N20.. good idea... Thanks.

My problem I think might still remain as trying to get down to 1/8" or less for a kitchen knife might be pushing it. Maybe the way I'm doing it with thin nickel sheet?

I ended up grinding this one down to more of a petty size and it will still work..
Click to expand...

No prob bro. Ive been a fan of your knives for a while, so glad to help. I think the nickel sheet could work. How are you keeping the oxygen out of the billet? Welding the seams or canister weld?
 
First it's diffuse not migrate.
There isn't the attraction of carbon to nickel as there is to carbon and other elements so there would be some difference in diffusion .However there will be diffusion as seen in carburizing grades of high nickel alloys such as 9310. There won't be the carbides with nickel.
I don't think you can properly keep the layers the same thickness throughout unless you do it with a rolling mill.
 
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