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Is stress relief baking necessary after machine grinding of hard chrome plating on high nickel alloys?

Hello, I work at a depot level organization involved in the refurbishment and overhaul of aircraft parts. I run into situations where the same part may be steel, stainless, or very high nickel content. When a hard chrome surface needs replating, and finish grind, what is the risk of grinding stress damage? How do these metals rank in susceptibility? Last, which is more risk important, type of metal or hardness? Do you know of stress relief standards for these alloys?
Thanks for any advice.

Gary Harper
product specialist - San Antonio, Texas, US
October 19, 2010

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Since you work for an overhaul facility, you must follow the overhaul manual to the letter to certify the repair. All OEM's have a standard practices manual that includes plating procedures or makes reference to some plating specification.

Your substrate metal and its hardness will call for a minimum of post plate bake. Some parts require a preplate stress relief cycle and some parts also require steel shot that includes an Alman strip for quality control before plate.

Have your supervisor get you the required manuals or verify that the process sheets are correct for each part/material.

I find it hard to believe that some irate ex employee has not reported your firm to the FAA. Have you asked all of the correct questions about your training?

James Watts
- Navarre, Florida
October 20, 2010

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Thank you, but that's not what I'm after. In a recent response (letter 1747) there was a reference "...present aircraft standards and AMS2406" and the comment made was ..."Chromium plate, ...heat treat...final grind, heat treat 1 hr at 190c to relieve grinding stress," I couldn't find that post plate, finish grind standard in 2406L or AMS2460. Am I missing something?
The other part of my question reflects the lack of information covering non-(less?)ferrous alloys and the effects of post plate processes.
Thanks,

Gary Harper
- San Antonio, Texas
October 21, 2010