I cryo treated a set of "Super Duty" brake rotors I used on a 1999 Crown Victoria.
This was my daily driver. One of the clipers failed pretty early, around 25,000 miles, causing some issues, warpage to the disc, and basically burning down that wheels brake set up.
I shotgunned the whole system to prevent any further troubles.
I purchased brand new Raybestos brand "Super Duty" drilled and slotted rotors all around and had them treated.
I was skeptical but figured this would be a good test because I had a 1992 Crown Vic with the same brake set up that had regular issues with the brakes, warping discs, wearing out quickly, troublesome pads...lots of irritating little stuff.
The rotors were checked for trueness prior to the cryo treatment and then again after, and surprisingly only one rotor needed a very slight adjustment. The others were still true.
I installed the rotors and some performance pads and that Crown Vic would brake like crazy, with no fade, no pedal modulation, very little noise, and no trouble for the life of the discs.
I rand two are three sets of pads through that brake set up while not having to do anything to the rotors....They were checked, but nother needed to be done.
Eventually though, rust took its toll. The rear discs went first because the internal brake drum style emergency brakes are prone to giving troubles.
Then, about three years later the front discs went due to rust also.
At the time of treatment I did paint the discs with high temp paint to mitigate rust, but Minnesota winter salt eventually ruins everything made of metal.
In the end I thought the treatments did provide a longer life to the discs.
By the way, I initially chose to try this based on a friend who vintage races a Shelby GT350.
He used to go through two full sets of discs and drums per race season.
After cryo treatment of the drums and discs he would get three or four seasons out of one set.
It was mentioned above, and is worth repeating.
Cryo treatment to metals does change the grain structure and can help with stability, wear, and ultimate strength....but it will not make crappy metal into good metal.