Etching trouble

G

grizzled gizzard

Joined
Aug 31, 2010
Messages
726
I forge 52100, differentially harden it, and then etch with PCB Etchant from Radio Shack.

The problem is the shiny, mottled portion, upper center part of blade. It should be light gray, like the area around it.

Looking at it under 60x, I can see that what is shining. It looks like little, very shiny, round balls. Could be carbides?

Does this look familiar to anyone?


053_zps62cb1241-1_zpsc4659a4c.jpg



Thank you for any thoughts.
 
IF I had to guess, I would say "De-Carb".

Try grinding/sanding a tad bit more, then re-etch.

Robert
 
I've tried re-grinding, with an A10 Trizact. Doesn't help. It is not any kind of contamination.

Wet sanding with 600-800 grit paper and etchant does work somewhat, but I'm trying to find the cause.

Thought someone else would have figured this out before.
 
grizzled gizzard said:
I've tried re-grinding, with an A10 Trizact. Doesn't help. It is not any kind of contamination.

Wet sanding with 600-800 grit paper and etchant does work somewhat, but I'm trying to find the cause.

Thought someone else would have figured this out before.
Click to expand...

Well Hoss,

An A-10 Trizact is probably somewhere around 1500 Grit. You say that 600-800 grit helps somewhat.

If you are looking for a magic answer, you ain't gonna find it here.

Do yourself a favor and drop down to at least a 100 Trizact, then go through the finer grits.......... Re-etch, and I think you will see a difference.

grizzled gizzard said:
Thought someone else would have figured this out before.
Click to expand...

Maybe they have figured it out before and are only trying to help. Or better yet, pay no attention to what I just said.

Robert
 
Grizz,
There are several possibilities. The most likely is that you are seeing artifacts of scale forged into the blade, or decarb from the hardening. Sand with a 120 grit Blue Zirconia or 100A Trizac belt and it will probably go away.

The other thing you mentioned is that the blade was "Differentially Hardened". If you truly mean that ( and not "differentially tempered"), then the upper part will etch at a completely different color than the edge, as pearlite etches different than martensite. If there are spots or stripes of martensite floating on the surface of the pearlite, they will etch differently,too.
Carbide banding/pooling is a possibility, depending on what the HT was like, but I doubt that is what you are seeing.

Sand it back at 120 grit and then back up to 400 and re-etch. Let us know what the result is.
 
Thank you very much, Gentlemen.

I'm very sorry to have dismissed your suggestion, Robert. Totally my bad. I didn't think.

I will finish grind a couple more, going through a progression.

I understand now that de-carb from hardening can go deeper than I thought.

Again, my apologies, Robert, and Thank You, Stacy.

I'll try not to be a stubborn ass anymore.
 
No apologies necessary Grizz. Due to my age, I have earned the right to be a bit "Crotchety" at times, and can seem to come across a tad "gruff". Why, there ain't a mean bone in my body.......... The mean ones were all broken over the years. :)

Work on that (suspected) de-carb and let us know how it comes out.

Robert
 
Can't thank you guys enough, you were 100% correct!

I did exactly as you said, and I got exactly what I was hoping for.

Thank you so, so much!

Succcess001_zps96ada6d3.jpg
 
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