etchant, CRES, welds 1

[dho]

1) The best etchant formula to reveal the weld penetration of 304 stainless steel ?
2) After etching, will the HAZ show up too which confuses the reading for penetration ?
3) The underlining etching mechanics?
thanks.

 

[CoryPad]

1. Without more details, this is not an easy question. Electroetching with 10 % oxalic acid, Kalling's, Beraha's, Ralph's, and others are all possibilities.
2. Weld metal/fusion zone should be distinct from HAZ after etching.
3. Different mechanisms are present for different etchants. Anodic dissolution of grain boundaries, sulfide film formation, and others are present.

 

[metengr]

(1)If this work is being done in a metallurgical lab, the best etchant is 10% oxalic acid, electrolytic.

(2)The HAZ will exhibit some networking of carbides along grain boundaries.

(3) read here

https://www.cartech.com/news.aspx?id=578

or

http://vacaero.com/information-reso...of-phases-in-stainless-steels-by-etching.html

 

[gtaw]

Thanks metengr!

Best regards - Al

 

[EdStainless]

Carbides will only be present if you have high enough carbon and the cooling rate is slow enough.
A light electrolytic etch in 10% oxalic acid will work well, don't over etch.
Most etchants rely on differential attack rates for various phases/orientation/compositions.

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P.E. Metallurgy, Plymouth Tube