Source: VAC AERO International, Inc.
Part discoloration after vacuum heat treating? What can heat treaters do to prevent this? In this best of the web, Q&A-style article, witness the heat treating industry gather around to exchange ideas and find a solution to the problem. Part position, backfill gas level, contaminated quench gas, or an air leak could all be to blame in this Technical Tuesday.
Dan Herring weighs in on the issue as well. To read The Heat Treat Doctor's® diagnosis, click the link below. Learn how the color and position of the discoloration give clues as to the source of the problem.
An excerpt:
"So, what else could be happening? Let The Doctor add a few thoughts to the discussion. First, the fact that the discoloration (staining) is brown in coloration suggests that the oxide is forming on the part surface during cooling when the temperature is in the range of (approximate) 245ºC – 270ºC (475ºF – 520ºF). This is supported by the fact that the oxidation does not occur “during natural cooling” (which we assume to mean cooling under vacuum). Second, the fact that the discoloration is more evident at the bottom of the load suggests the phenomenon is (gas exposure) time dependent, that is, the longer the parts take to cool through the critical range, the greater the chance for discoloration."
Read more: Discolored Work in a Vacuum Furnace – The Heat Treat Community Answers the Clarion Call
Find heat treating products and services when you search on Heat Treat Buyers Guide.com
