Andrew: Your question is a tough one in the context of a discussion forum. However, as a wild guess, Elgiloy includes 20% Cr, sufficient to naturally form a chromium oxide film, given sufficient oxygen potential. Perhaps a thicker oxide is forming on the machined surfaces due to heat buildup from the machining process. Hope this helps! David Hendrix The Hendrix Group Inc.

Dave, Below is our annealing process: (1) Vacuum < 5 microns Hg. (2) Warm up from 1000F to 2130 F in less than 40 minutes. (3) Hold in range from 2130F to 2160F for 6 - 8 minutes. (4) Quench in Argon gas from 2130F to 1000F in less than 6 minutes. (5) Quench in Argon gas from 1000F to 400F in less than 10 minutes. We run 2500 parts at a time in one dedicated oven (each part is about the size of a quarter and .060" thk.) Our contamination issue only happens about 3-4 times a year yet when it does appear, a whole lot of 4k to 6k parts have to go through an expensive chrome-etch rework process to clean up. Again, the contamination is only in the conventional machined areas. We wire EDM a feature on this coin after our annealing process and this feature has never had any chrome-oxide contamination on it. This kind-of explains why the focus of my investigation has been on our annealing process and a possible outgassing or heat scale forming on the elgiloy material. Thanks for your help/suggestions, Andrew Waldow RBA-500 Manufacturing Engineer Defense & Space Electrical Systems - Redmond Phone: (425) 242-2598 Fax: 425-885-8115 andrew.waldow@honeywell.com