W2 with a hamon showing strange marks

Barry Clodfelter

Barry Clodfelter

Joined
May 29, 2007
Messages
571
I have been working on a camp knife forged from W2 and hardened with clay to create a Hamon. I took the blade to a very clean 800 grit finish the first time before the etch and the lines in the first pic showed up. Thinking that I may have just missed them the first time I went back and started at 400 grit and went up to 1200 and the lines are not there before etching. I took the knife outside in the daylight and used an optivisor and the lines are not there. Any ideas what these could be? I don't use a lot of W2 and have never seen anything like these before.

Capture1.jpg


The knife is in three pieces and just stuck together for this pic.
20191130_122304-scaled.jpg
 
It's an unfortunate occurrence with W2. I don't know what it is, or why it happens, but I've had it and many others have as well. It *really* looks like errant scratches so it's easy for people to dismiss, but it's not.

It seems to only appear in the pearlite of a hamon, and only when etched, which leads me to believe there is something going on that chemically reacts to the acid differently than the surrounding material, but I have no idea what.

Just another reason I quit using W2.
 
Thanks kuraki that makes some sense and also makes me a little afraid to use the chuck of DH III W2 I have been saving.

I have never seen that on a hamon in 1095 so maybe I will just make hamons on 1095 and fully harden the rest of the W2 I have.
 
That is curious... If they aren't scratches or burnished metal, why are they repeated on the ricasso and plunge, in perpendicular directions? I'd like to see Don Hanson III Don Hanson III 's comments as well.
 
I just knocked off the oxides from the etch at 800 grit and they are gone. This is how it looked before the last 2 etches. That is as clear as my phone would do so close up.

20191206_134837-scaled.jpg
 
How much did you sand off prior to HT and after? Could it be that those etch "ghost marks" are decarb from the "valleys" of the previous scratches? Am I explaining that right?

I only say this from experience with "forged close to finish" blades. Even after grinding what I thought to be deep enough, I've seen hammer marks rise from the dead.
 
@Rick Marchand interesting thought! I am not sure how much was ground off before or after HT. I forged and HT the blade in January and am just getting around to finishing it. I did surface grind it before hand sanding but I really didn't pay much attention just got thru the decarb to clean steel across the length.

@Josh Rider man I am saving my only tiny piece of the good W2!! This is just plain ole Aldo's W2. LOL!
 
Nice work Barry. I don't have an answer but I'm paying close attention to what the conclusion turns out to be. I have a box of DHlll rounds that I have been saving until I'm good enough. :)
 
I've be fighting this for years, but it doesn't happen on every blade. Ghost scratches. It happens in the grinding stage after heat treating. The grit from grinding is affecting the steel right at the bottom of the scratch, work hardening maybe? If you keep etching and hand sanding they will go away, but that's a pain!

My son Kyle makes more W2 knives than I do and he's never had this problem, ever. I am heavy handed when grinding and quick, he is more light handed and takes much longer to grind a blade.

So heavy grinding pressure on a hard platen seem the be the cause.

I never see this with a W2 blade hollow ground on a rubber wheel, just flat ground on a hard platen.
 
That's an interesting idea. Work hardening at the surface. I also grind hard and fast. It would certainly explain why they look so similar to grinding scratches.
 
Don Hanson III said:
I've be fighting this for years, but it doesn't happen on every blade. Ghost scratches. It happens in the grinding stage after heat treating. The grit from grinding is affecting the steel right at the bottom of the scratch, work hardening maybe? If you keep etching and hand sanding they will go away, but that's a pain!
Click to expand...

Thanks Don!! I like calling them ghost scratches. My daughter is fascinated by ghosts and she got a kick out that! I agree it is a pain and after going back to 220 yet again they still showed up. I gave up and just finished it with out the etch. The hamon is still there but not developed. I just couldn't let this one go out with what looked like scratches on it. Still need to clean up the rest of the epoxy squeeze out but this is how it turned out.

20191209_181612-scaled.jpg
 
Nice knife! :thumbsup::thumbsup::thumbsup:
I also think those ghost scratches might be caused by work hardening or otherwise damage/modification of the underneath steel's crystal structure due to low grit grinding in the early shaping steps. Those are features i believe can pop up through etching.
There you find an interesting view on a micro scale of this behaviour:
https://scienceofsharp.com/page/2/
 
Don Hanson III said:
Very Nice looking knife Barry!
Click to expand...

Thank you Don!

stezann said:
Nice knife! :thumbsup::thumbsup::thumbsup:
I also think those ghost scratches might be caused by work hardening or otherwise damage/modification of the underneath steel's crystal structure due to low grit grinding in the early shaping steps. Those are features i believe can pop up through etching.
There you find an interesting view on a micro scale of this behaviour:
https://scienceofsharp.com/page/2/
Click to expand...

Very interesting article stezann, thank you. It explains a lot more of how grit interacts with the surface at a level we cannot see. Had to read it twice and then bookmarked so I can go back.
 
I asked Kevin Cashen about this about 5 years ago. I remember posting it on Bladeforums, and seem to remember it being related to stress in the microstructure in the steel, like Don mentioned. I thought it was pre heat treat, but I will try to find the post. It was related to course grits, not finer grits too, iirc.
 
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