I was intrigued by your question, so I did a Google search on "cryogenic treatment of metals". It wouldn't be fair to you or the authors to try to summarize the various articles. One consistent thought that I did find was that the greatest advantage is in reducing wear, hardly the issue with CV joints. Another statement that stood out was that the process is of the most value when done before grinding and polishing.

I would suggest that you spend a couple of hours searching and reading.

Jim Paget
88 YJ with a few changes

www.rrr4x4.com