If the part was very small (under half inch) perhaps... , but I forsee a problem heating the part shaped like a bearing race evenly with induction coils. It would have to be suspended horizontally. (same plane of rotation as the coil). This complicated the release and quench mechanism somewhat.
Also, why use vacuum if you're going to use oil for quenching? Why not just fill it with argon at slight overpressure? This way your tube wouldn't have to be vacuum tight making it a lot simpler. However I doubt a part could be quenched in oil evenly enough to be used as a bearing race as is.
If you have no ability to precision grind it is much easier to plan for hard turning (with cheap Chinese CBN for example) after heat treat, rather then relying on no warpage). Still, a bearing race is a difficult project. I would suggest something else for a start.
Vacuum heat treatment is used not only because vacuum is good at preventing oxidation, but also because it enables use of gas quenching which quenches the parts from all sides at the same time with no need for any movement. If I wanted to experiment with small scale vacuum heat treatment I would do it with gas quenching rather than oil for sure. One could use argon, nitrogen or maybe even carbon dioxide (due to low cost) under pressure for the quench. Instead of using heat exchangers and sending the gas in a loop like they do in big furnaces. One could just expand the pressurised gas into an intermediate chamber to pre cool it and send it through the furnace still at significant overpressure (few bar) to assist venting. And vent the furnace to atmosphere. Now that I think about it, maybe the whole thing could be done without vacuum in the first place if the furnace is small...
Make your tube in a way that you have your inert gas port on bottom end, have an overpressure gate that will blow open and stay open at a certain overpressure (let's say 1.3 bar) on top. Have a large diameter (1in) copper expansion chamber next to your inert gas inlet on the bottom. And have a tiny hole in the chamber on top to allow argon to flow slowly, but have it small enough it doesn't prevent buildup of pressure when lots of gas is introduced.
Put, let's say constant flow of argon at 5l/min through the furnace tube. Do your heating cycle. When ready to quench send your pressurised quenching gas from a high pressure bottle, through a high pressure regulator (there are nitrogen regulators available that can be set up to 50 bar on the low side) through a nozzle into that expansion chamber, the moment the pressure in the tube reaches 1.3 bar the valve on the other end blows open. Your cold gas flow does the quench. Job done.
If I was serious about it I would look for literature on gas quenching first. I would be very surprised if there isn't a lot of research on this.
