Etchant 1

[cjgrass]

I need to etch API 5L X65 pipe that is lined with Inconell Clad 825 that has been GTAW/FCAW welded with ERNiCrMo3 filler material for Vickers Hardness and CVN testing of the weld metal and fusion line. Any suggestions?
Thanks.

 

[EdStainless]

Just about anything will etch the steel and not touch the high alloy materials, this will make the fusion lines easy to identify. Start with 10% Nital.

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[redpicker]

2% to 5% nital (2% to 5% nitric acid in methanol or ethanol). Like Ed said, it isn't going to touch the higher alloy material.

rp

 

[cjgrass]

Thanks guys, yes I use nital frequently for carbon steel in the 5 - 10% range. I also need to see the fusion line of the clad lining in the root area of the welded joint that is clad to clad the specification requires hardness readings to be withing 0.25mm of the fusion line. The weld joint is .750" of the X65 and .125" of clad to clad at the root. Is there anything that will etch both materials and still leave the sample suitable for macrographs after the hardness survey.

 

[metengr]

Try electrolytic 10% oxalic acid etch.

 

[metengr]

I would send the weld coupon to a local metallurgical lab and have them etch it for you.

 

[EdStainless]

The 825 is barely a stainless steel, it will still tint in nital (use ethanol).
The Ni based filler should have enough higher resistance to be identifiable.
In the lab I would use electrolytic etch, lots of options but probably something stronger than oxalic.

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