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Etching method for cobalt chromium L605 alloy

January 30, 2008

I am currently conducting a research about cobalt chromium L605 alloy etching. I have to etch the treated specimens in order to observe the microstructure of the alloy. The etchants should reveal the grains but not harm the compound and/or diffusion layer. I have tried;
1. 30%HCL + 20%H2SO4 + 50%DIwater
2. 40%HCL + 30%H2SO4 + 30%DIwater
3. 45%FeCl3 Solution
4. Pure HCl
and I have heated the specimens (about 80 deg. cel.), heated the etchants, etc. so far. But none of these methods/etchants worked out for me.
Here we want to nano surface layer on our specimen.
Please suggest us which etchant is suitable for CoCr L605 Alloy.

Bhavesh Pastagia
Student - Surat, Gujarat, India

The company that makes your polishing equipment will give you lots of help in this area.
Since I do not know the percentages of this alloy, I can not make a guess. The L for lead ? does not help and might require a fluoride etch like dilute fluoboric acid.

My guess at this time is that you are going to use about 1.5 volts for a few seconds with a dilute acid mixture.

Check your library--ASM has a large book of photomicrographs and procedures.

James Watts
- Navarre, Florida
January 31, 2008

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