Dear Collegaues
Could you recommend the best stop-off paint for low pressure carburising when used in excess.
I did try Acheson stop-off C4&HT which is commonly used for gas
carburizing, I tried Condursal 0091 and LUISO W44. Most of our
components are stopped-off in 95%, so carburising area is very small.
Excess of stop-off paint creates a lot of carbides in microstructure.
I did several trials using diffrent acetylene levels and I can not have
any influence on this. Any recommendations, what to do to improve our
processes? Is it down to correct stop-off or shall we try to optimize our
process?

Just a few thoughts since no one else has replied. Have you tried the “No-Carb Green” product from Heatbath/Park Metallurgical (www.heatbath.com)? Although I don’t have any personal experience with it, it is advertised as being good for vacuum carburizing. Another thought is that if you have very small areas to carburize and large areas to protect, perhaps you should leave stock on the rest of the part and machine it off after carburizing. Good luck.