Etching 304ss - x20 1

[deco0404]

Hi guys,

I have a job coming up to take a site replica of 304ss welded to x20(11Cr, 1Mo, 0.25V). I usually use vilella's for x20, p91 etc....and oxalic for 304, but have not come across two together before. Has anyone done this or something similar.

I'm thinking I will probably need to take two replicas, first with Vilella's and secondly with oxalic

any advice would be very welcome

Declan

 

[unclesyd]

Is this from a test coupon or actual weld?

If this is test coupon do you have fume hood available?

 

[deco0404]

it is an actual site weld inside a boiler...no fume hood, but could organise a welders extractor if necessary....

 

[unclesyd]

I'm trying to find a recipe for an etchant based on HCL + ???. I thought I knew where it was but my memory failed me, hopefully someone will jump in with the composition. I think we used HCl + H2O2 or in some cases 1:1;1 Aqua Regia.
You may have to swab each material with a specific etchant such as the ones in your OP. I believe that the weld metal is going to be the tough one to etch.

 

[Guest102023]

If the fusion line is reasonably straight I have done:

1) mask the lower alloy side with regular Scotch tape
2) etch the higher alloy side
3) remove the tape and etch the lower alloy side (the etchant for that will act much more slowly on the higher alloy material

 

[SMF1964]

The two replicas may be the way to go.

Are you electropolishing for the surface prep or mechanical polishing? If you are electropolishing, couldn't you use the electrolyte as your electrolytic etch? I've done it with stainless steel and with nickel-based weldments, but not yet tried it on something like the Cr-Mo-V alloys like P91.

 

[deco0404]

Thanks for your input guys.

As this was a site weld we were polishing mechanically and went with two etches, as it turned out we might have got away with just using vilellas, as this etched the HAZ of the 304 ( which is what we needed to see). We knew it would have no problem with the X20, but were kind of surprised with the results anyway. The vilellas however, didnt etch the 304 outside the weld and heat affected zone & didn't leave any imprint on the weld at all. The oxalic did look after this though.

Declan