etchant for Cr-Mn (austenitic) stainless steel 1

[zedomonte]

Hi. I'm working with a Cr-Mn (austenitic) stainless steel and I would like to know your opinions on witch etchant to use on this material. Any help is welcome.Thank you.

 

[NickE]

I think it really depends on what you need the contrast for. I've used Viella's with some sucess on 17-7, others listed by my LECO Metallography reference are:

102 -- Concentrated NH4OH Electrolytic 30-60sec@6V -- Attacks only carbides.

89 -- 10mL HNO3 + 10mL Acetic Acid + 15mL HCL + 2-5drops glycerine. -- general structure.

There are a bunch listed also that chnge with regards to chemistry of the steel (300, 200, etc...)

 

[TVP]

Buehler and Struers both have a considerable amount of information available on their websites. Glyceregia is probably the most commonly used/recommended etchant for austenitic stainless steels.

 

[zedomonte]

This is the steel's composition.

C (%)0.037
Cr (%)18.02
Ni (%)3.72
Mo (%)0.02
Mn (%)0.13
Si (%)6.9
P(%)0.35
S (%)0.003
N (%)0.157

 

[EdStainless]

Is that a typo? 7% Si??? Shouldn't it be 7% Mn?

I would use electrolytic Oxalic acid. We do a lot of high Mn grades and it works fine.

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http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[NickE]

for the 200 series steels (Fe+ 16-25Cr+ 3-6Ni+ 5-10Mn)
there are four etchants listed.

#'s 103,104,98 -- Delineates sigma phase and ferrite welds of dissimilar metals

#86 for chemical polish & etch.

for general structure of Stainless in general there are 10 etchants.

#'s 13b, 89, 87, 88, 83a, 80, 94, 95, 91, 101.

for carbides and sensitization there are two: #'s 13a,102.

The common named etchants are:
104-Frank's
98 -Murakami's
87 -Glyceregia
80 -Vilella's
94 -Green Contrast & Kalling's 2
95 -Kalling's 1
101-Chrome regia

Leaving:

13 -- 10g oxalic acid, 100ml H2O
     -- Electrolytic at 6V
        a) 10-15sec
        b) 1min
83 -- 10g CrO3, 100ml H2O
     -- Electrolytic at 6V
        a) 5 to 60sec -- attacks carbides
88 -- 10ml HNO3, 20ml HCl, 30ml H2O
     -- CAUTION can give off NO2 gas, discard solution
        before it becomes orange. USE FUME HOOD.
        Stronger reaction than Glyceregia.
91 -- 5ml HNO3, 5ml HCl, 1g picric acid, 200ml methanol or ethanol (95%)
     -- Same as 1:1 misture of 80(Viella's) & 74(5%HNO3&Methanol)
103-- 20mlHNO3, 4mlHCl, 20ml methanol(99%)
     -- Immerse 10-60 sec

WARNING -- I AM NOT RESPOSIBLE FOR WHAT YOU ARE DOING, THESE CHEMICALS CAN POSE A SERIOUS THREAT TO LIFE AND HEALTH AND REQUIRE SPECIFIC PRECAUTIONS. PICRIC ACID POSES AN EXPLOSION HAZARD.





Nick
I love materials science!

 

[Maui]

I echo Nick's warnings at the bottom of the previous thread. Picric acid, when not in solution, can present a serious explosion hazard. Oxalic acid etching releases poisonous fumes. Please consult the appropriate MSDS sheets before working with any of the above etchants. When used improperly they can pose a serious threat to your (or someone else's) health.

Maui