Pattern Welded Steel, Elements and Etching

[David Wesner]

Hi Guys and Gals

I have a couple questions regarding the finished appearance of the many different materials we use to make our pattern welded steel.

I've been making knives for a several years and just recently picked up a press.
The past 4 months have found me focusing mainly on sound forge welding technique along with basic pattern development.
Until now I've been using Aldo's 1084 and 15N20 exclusively. I use a diluted solution (~ 6-1) of distilled water and ferric chloride as my etchant.

Now I would like to make a bit of bolster/guard/furniture stock, so I picked up some nickel from Kelly C.

I understand the nickel in the 15N20, when etched, is what shows as the bright lines. The monel nickel 200, I'm told, will show even brighter than 15N20 after etching.

Using 1084 as a baseline in regards to shade of grey/black ......

Question # 1 : What does carbon content in a material component do to the finish etched color shade ? More carbon = darker shade ? More carbon = lighter shade ?
Just to be clear, what can I expect to etch darker, 1095 or 1084 ?
To go to extremes, what could I expect from 1018 (obviously not blade stock) when etched, in comparison to 1084 ? Much lighter gray, or much darker black ?

Question # 2 : What other elements, besides nickel, have a noticeable and more or less, "predictable" affect and what would that affect be ? Brighter,darker ?? FWIW, I completely understand that finishing technique can have an appreciable affect on the finished color shade appearance. In other words, I'm aware I can scrub or sand a majority of the deep black oxides off of an etched 1084/15N20 blade. However, I think we can agree, after etching and finishing there is still a noticeable degree of difference from one material to the next.

Thanks for any help and tips you can help me with in regards to my questions. I really, really appreciate it :thumbup1:



:42:

 

[EdCaffreyMS]

Question # 1 : What does carbon content in a material component do to the finish etched color shade ? More carbon = darker shade ? More carbon = lighter shade ?
Just to be clear, what can I expect to etch darker, 1095 or 1084 ?
To go to extremes, what could I expect from 1018 (obviously not blade stock) when etched, in comparison to 1084 ? Much lighter gray, or much darker black ?

Most of the Plain Carbon steels are going to come out of the etch looking optically the same as far as dark/light shades. You MIGHT see some minor differences when comparing opposite ends of the scale where carbon content is concerned, but it will not be majorly different.
What will create a noticeable difference in how these steels appear after etching, is whether they have been heat treated/hardened prior to etching. Again it will not be an "earth shattering" difference, but it will be optically noticeable.

Question # 2 : What other elements, besides nickel, have a noticeable and more or less, "predictable" affect and what would that affect be ? Brighter,darker ?? FWIW, I completely understand that finishing technique can have an appreciable affect on the finished color shade appearance. In other words, I'm aware I can scrub or sand a majority of the deep black oxides off of an etched 1084/15N20 blade. However, I think we can agree, after etching and finishing there is still a noticeable degree of difference from one material to the next.

About the only other element that I am aware of that will effect how the etched finish of a particular steel will appear is Chromium...it will have a parallel to that of nickel, but to a lesser degree, and over a more narrow band. When Chromium and some other elements such as Vanadium and/or Moly are contained in the alloy, it will also produce different optical effects in the etched product.

The most reliable, predictable, and effective means of creating contrast is varying degrees of nickel within an alloy.

Another direction that you can take to effect the end appearance is something such as a coating like "baking lacquers". Such as this:

Here's an example of what 416SS over a 1084 core looks like fresh out of the etch:

Even with the 12-14% Cr in 416, it still etches, but produces a "frosty" appearance.

 

[Doug Lester]

I have had discussions on contrast caused by differing carbon content in damascus billets with some metallurgists on this and other sites. The consensus was that by the time you finish the multiple forge weldings it takes to creat the billet the carbon content, due to it's migration within the billet, will be homogenous throughout. If you end up with any contrast it will be caused by the alloying elements in the steels used. With the 10XX series that will be the difference in the manganese levels which diffuse very much more slowly than carbon in steel.

I did ask why then does cable damascus show watering when the composition of the steel in the wires is exaclty the same and was basically told that it was still under study.

Doug Lester

 

[Stew]

I've been lead to believe that manganese levels play a big part on colour as well.

Gotta say Ed, that stainless / carbon san mai is a beauty!

 

[David Wesner]

Thanks a lot Ed and Doug.

I've heard and/or read the same in regards to carbon levels evening out after only a few folds. I don't know why it didn't occur to me that would probably make most plain carbon steels etch pretty much the same.

Sounds like the answer I'm looking for can only come from experimenting, practice and just doing it.

It's funny, I bet like you guys, that's how most of the answers to my knifemaking questions have come to me over the years

Thanks again guys !

 

[David Wesner]

Thanks Stew. I'll make a note of that.

And yes, ditto that !

I meant to mention what awesome looking blades those were Ed !

 

[EdCaffreyMS]

You guys are correct on the Mn content....the reason I didn't mention that is because the majority of the steels we us when creating Damascus or other forge welded combinations have a relatively narrow range of Mn. If you did find a steel with higher than average Mn content, there will be "side effects" that may force you to change your process(es), which more times than not will force you to choose one of those "trade offs" that I'm always talking about.

Doug: The watering effect that you see in cable comes from the decarb at the weld lines....the guy who does my spectrographing answered that one for me a number of years ago. (I wanted to know the answer to that question too).