You may try Tool-Flo in Houston. They do various different coatings on coustomer supplied parts. Another place to try is Body-Kote in the DFW metroplex. I know of a place or two that does "Hard-Kote" which is a boron coating, on oilfield parts. It will change your heat treat because if the heat generated during the hot spray process. And far as I know, it can't be re-heat treated once applied.