I am by no means an expert in this area, but I do have a fair amount of experience with the bone and charcoal process. Some observations that I have made are that it is quite possible to get very good colors without actually getting the surface substantially hard. I did this last semester with a piece of 1095 that went in the quench at around 1250 and came out with beautiful colors, but it was soft enough to cut easily with a file. The problem is that if you are not hardening the surface you really aren't performing color case hardening. My research suggests that many older firearms had fairly superficial hardening, but they were still hardened. I have seen the site dealing with the Marlin restorer and find it very interesting, but I don't totally buy into his thoughts that these guns were quenched at these very low temperatures. I have found you can get very vivid colors at a temperature range that still hardens the surface, namely something over the critical temperature. At higher temperatures (over 1500 degrees) the colors start to diminish rapidly. I have never had a problem with warpage on the parts we have done, but if they are critical I make sure to block them appropriately. I cannot really imagine sending a rifle or shotgun action into the quench tank without some thought given to this possibility.
I am also a big fan of tempering the finished parts at 400 degrees for at least one hour following the quench. I think this helps in two ways, one it enhances the colors, and two, if by chance the part was a high carbon alloy it should help to prevent it breaking from excessive brittleness.
Will,
Thank you for your generous offer, but since I do most of my casehardening in a university lab with students I would not be able to work on firearms parts. Hopefully the information that I gather can be used by others in this area however.
Regards,
Alex Johnson
Last edited by Alex Johnson; 09/11/08 06:28 PM.
