17-7 SS discoloration

[Aubryann]

hello everyone.

I have surgical parts that are 17-7 SS (.050 thick)annealed that were heat treated per RH 950 to RC 45 min, but they were not heat treated in a vacuum atmosphere as directed so they are discolored. Our in-house cleaning methods will not work. Is a bright dip a good recommendation? and if not please advise other recommendations...thanks for your help.

Aubry

 

[TVP]

The problem with acid cleaning is the potential for hydrogen embrittlement. Acids that are modified to contain an inhibitor can be used if the immersion time is kept to a minimum. Some standards specify the immersion time to be 5 minutes maximum. The following document from SurTec has some good information on the subject, including some specific inhibited acid cleaners that they offer:

http://www.surtec.com/TB/TB08E.pdf

 

[Compositepro]

Electropolishing is commonly used for SS and I expect it would work for you.

 

[unclesyd]

There is some valuable inforamtion on the cleaning of 17/7 SS on the AK Steel site. Cleaning prior to hardening is of the upmost importance. Ive seen more than one piece of PH SS with someone's finger print.

In the section about using HNO3/HF the following statement is very important as a means to shorten the process.
"Removal of loosened scale may be facilitated by the use of high-pressure water or steam spray." This has to be done before the parts dry down.

We make a lot of PH SS parts every year and our procedure for processing after machining is Vapor degrease, harden, and acid pickle with HNO3/HF. The immersion time we use is around 10-15 seconds and use a steam spray to knock the loosened scale off. After we throughly rinse in pure water and dry down.

Look at the 17/7 Data Bulliten

http://www.aksteel.com/markets_products/stainless_precipitation.aspx

 

[mfgenggear]

how about a light bead blast, or aluminum oxide blast of it's bad