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Effects of electroplating Silver on the Hardness of Steel

I am a QA Specialist for the Navy, working with Receipt Inspection of components from vendors for use in the submarine fleet. I am having trouble with apparent changes in Hardness to AISI 1005 to 1012 Steel after being Electroplated with Silver. Hardness of the Steel before plating is approximately 54 HRB, as reported by the vendor. After plating with Silver per ASTM B700, .0010 to .0015 thick, Receipt Inspection reports the hardness is anywhere from 56 to 94 HRB. Can you confirm the likelihood that this change in Hardness is caused by the Electroplating process?

Bruce Hilton
Government QAS - Portsmouth, NH USA
November 5, 2009

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No, it would go the other way, unless they are doing a bake cycle at a unusually high temp with a rapid cool down, making it a hardening cycle.

The best guess is that one of the 2 hardness testers is not being operated correctly with an outside chance that one machine is badly out of calibration. With the massive range that you are getting, I will suspect that the problem is at your site.

James Watts
- Navarre, Florida
November 5, 2009

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Sorry, I was a bit misleading in my original post; the range of 56 to 94 HRB represents multiple pieces with this problem, not just one. Calibration is checked before every test.

So you say, if anything, the hardness value of the base material should be LOWER under normal process conditions after silver plating?

Bruce Hilton
Government QAS - Portsmouth, NH, USA
November 9, 2009

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November 9, 2009

Bruce, I assumed that you meant multiple pieces and not on the same piece.
The vendor of the steel certainly is not getting all of the pieces at exactly 54 RB. what range is he getting on the virgin parts?
54 B as I remember is rather soft compared to the C scale , so I have a bit of a problem assuming that it is heat treated (hardened),
The plater should be baking the plated product at something like 375F for 3 - 4 hours. This is on the low end of a tempering cycle and should lower the hardness by a point or two. Also, the silver is very soft and tho it does not affect the hardness much because it is thin, will lower the hardness a bit because it is massively softer.
I still think that there is a problem in the measurement at one of the sites and I would look at your site as the more probable since you are getting such a massive range of results. Not being disrespectful, but there is a lot of difference in taking the hardness of a test block and an improperly supported real world part.

In summary, silver plating and a bake cycle should both reduce the hardness of the part and I cannot fathom a smooth part with a 90% range of readings.

James Watts
- Navarre, Florida