Preferential electrochemical etching of the metal grains or grain boundaries
Preferential electrochemical etching of the metal grains or grain boundaries
(OP)
We are using a cyanide based electrochemical etching process to etch tapered tips on a precious metal alloy wire and have discovered that each material lot behaves differently with the same etch process. These material lots will preferentially etch the grains in one lot and varying levels of the grain boundaries in the next lots. We have etched these material lots in the same batch and have achieved the same grain boundary etch results. I have found out that that the lots we have purchased are from the same pour but were heat treated at different times. We have analyzed the exact hardness of the lots and found that the degree to which the grain boundaries is etched does not follow the hardness of the material. What material properties would cause the preferential etching of the grain boundary to varying levels or the preferential etching of the grains? The EDX that we had performed showed no differences in composition but that testing is qualitative anyway.





RE: Preferential electrochemical etching of the metal grains or grain boundaries
RE: Preferential electrochemical etching of the metal grains or grain boundaries
Maui
RE: Preferential electrochemical etching of the metal grains or grain boundaries
Maui
RE: Preferential electrochemical etching of the metal grains or grain boundaries
"Even,if you are a minority of one, truth is the truth."
Mahatma Gandhi.
RE: Preferential electrochemical etching of the metal grains or grain boundaries
Arunmrao- We sometimes etch the grains alone and some times the grain boundaries even though the same process is used. Could the grains sometimes have more free energy?
RE: Preferential electrochemical etching of the metal grains or grain boundaries
Maui
RE: Preferential electrochemical etching of the metal grains or grain boundaries
Which test would you recommend to use for the grain boundaries?
RE: Preferential electrochemical etching of the metal grains or grain boundaries
Maui
RE: Preferential electrochemical etching of the metal grains or grain boundaries
The variation could also be related to the grain orientation. Some directions will be attacked faster than others. You may need to look at grain size (by metallography) and orientation also (this would be XRD work).
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P.E. Metallurgy, Plymouth Tube
RE: Preferential electrochemical etching of the metal grains or grain boundaries
EdStainless- My current plan was metallography and XRD unless Maui states that a different test is required based on the composition.
RE: Preferential electrochemical etching of the metal grains or grain boundaries
Maui
RE: Preferential electrochemical etching of the metal grains or grain boundaries
RE: Preferential electrochemical etching of the metal grains or grain boundaries
You might also want to try re-heat treating some deliberately too hot and too cold just to see what variations you can generate.
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P.E. Metallurgy, Plymouth Tube
RE: Preferential electrochemical etching of the metal grains or grain boundaries
Edstainless- I will let our lab know.
RE: Preferential electrochemical etching of the metal grains or grain boundaries
Maui
RE: Preferential electrochemical etching of the metal grains or grain boundaries
Maui
RE: Preferential electrochemical etching of the metal grains or grain boundaries
RE: Preferential electrochemical etching of the metal grains or grain boundaries
I would still focus on segregation and secondary phases.
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P.E. Metallurgy, Plymouth Tube
RE: Preferential electrochemical etching of the metal grains or grain boundaries