Strange etching

[lyuv]

I"m trying to find steel to make damascus. Got my hands on a band saw blade and some O1, and I figured I"ll etch them to see it the band saw indeed stays shiny.

Took sample from each and covered 3/4 with tape. Into ferric chloride for 10 minutes, Removed 1/3 of the tape and repeat 2 more times.

So the sample has 4 sections - one exposed 30 minutes, one 20 min, 10 min and none,

STRANGE results:

1. On both steels there in no difference between exposure length (the slight differance in the picture is just lighting angle).

2. The band saw (bottom sample) got DARKER than the O1.

Any thoughts? insights?

BTW, For whatever reason, I failed to forge weld them.

[ThomasPowers]

I'm assuming you cleaned the test pieces just like you would for a blade?

Remember there is no world wide law mandating what alloy a manufacturer must use for their bandsaw blades.  I'd try several different ones from different sources.

Also with fresh pieces try a hot vinegar and salt etch.  Or HCl etch.

[Jclonts82]

First spend a few minutes sanding/polishing up the test steels. I find a nice fine sanding can give you more reliable results, usually at least 400 grit (about 40-45 mesh, or about 40 micron, whatever your local abrasives are measured in) then a rinse/paper towel with acetone to clean it of any oils, fingerprints included. After that dries I etch. What acid, and concentration, are you using for an etch?

[rhitee93]

In addition to the above responses, I'll throw out that steels will etch differently after heat treating.  I only use 15N20 and 1095, but before heat treating, the 15N20 tends to etch darker than the 1095.  After heat treating it will be the opposite with the 15N20 looking bright and the 1095 going dark.

[ThomasPowers]

Ferric Chloride diluted 50:50 or more (25 FC solution: 75 H2).  

Hot household vinegar saturated with  NaCl.

[lyuv]

HI all. Thanks for your thoughts.

The samples where deeply sanded. Not sure about the grit, but coarser than 400. However, after sanding they where handled with gloves and cleaned with alcohol. Also between immersions. So no oily contamination.

The feric chlorid was used as bought. No info on the label, but the seller claimed it's 40%. I"m not sure the concentration is the issue here, since it did etch. But it reached a limit within only minuts. This is the weird thing.

Interesting to learn about hardening influencing etching. The bandsaw sample was hardened, so it's probably nothing like 15n20.