AEB-L rusting

[Ryan Duran Geiger]

Hey, everyone.

I did some forged AEB-L stainless steel gyutos and petties recently, but the kurouchi finish on them is rusting, which didn't happen with any of my previous attempts.

Is it just an issue with forging stainless? Or did I mess up something along the way?

https://imgur.com/BUjLesS

Any input would be greatly appreciated.

Thank you,
Ryan.

 

[Stacy E. Apelt - Bladesmith]

How were they HTed?

Most likely that is caused by decarburized metal in the kurouchi that does not get ground away in finishing. This is basically a plain iron surface, and will rust easily.

 

[Ryan Duran Geiger]

How were they HTed?

Most likely that is caused by decarburized metal in the kurouchi that does not get ground away in finishing. This is basically a plain iron surface, and will rust easily.

Ahh, that was my worry. Guess it's time to go regrind them.


Clayed with Nuclayer no scale 2000.

Equalized at 1560 for 15 minutes, ramped up to 1950 afap and held for 15 minutes. Quenched in parks 50, followed by a plate clamp.

Dry ice and alcohol bath, followed by X2 temper at 300F, which put them right at 63hrc.

Thank you,
Ryan.

 

[samuraistuart]

While the Nuclayer no scale might be rated for 2000°F, I don't think Daniel (I think that's the maker's name) meant for it to be used on stainless, just carbon steel. I'll put it to you this way, when I started HTing stainless, I used ATP-641 anti scale/decarb compound that is rated for 2300°F. It works really well on carbon steel, but there is a significant layer of decarb when using ATP on stainless. I would seriously consider using the SS foil. Once I switched to SS foil, the decarb issue went away. The closer in temperature you get to the max rating of compound the less effective it seems to be. Just my 2 pesos.

 

[Alex Topfer]

Most likely that is caused by decarburized metal in the kurouchi that does not get ground away in finishing. This is basically a plain iron surface, and will rust easily.

I thought the corrosion protection was due to free chromium in the steel? so why does removing the carbon allow it to rust, or does de-carb also remove the chromium?

 

[Stacy E. Apelt - Bladesmith]

The thin layer of decarb probably has little or no chromium in it. It is low carbon to no carbon steel ( iron).


Additional info:
Decarburized steel will not etch like carbon steel does, either. It will show up as a gray surface. This is especially an issue with damascus blades. The decarb has to be ground away to expose the layers of damascus below it.

 

[JTknives]

I highly recommend removing the soak at 1560 and just pop the blade in at austenite temp. I’m not quite sure why people do this as it’s normally only used for large items like punches and dies that have a rust of cracking if heated to fast. I could see running an annealing cycle on the AEBL to get the structure back down to what you want befor heat treating but ditch the pre soak.