Processes for producing peening media, the peening media produced from such processes, and methods of using such media. Particles are provided having surfaces that are formed of or contain a metal that exhibits solubility for oxygen in a metallic phase so as to increase in surface hardness as a result of solid solution strengthening due to oxidizing of the surfaces of the particles. The particles are subjected to a thermal process in an oxygen-containing atmosphere at a process temperature and for a process duration sufficient to oxidize the surfaces of the particles to increase the surface hardness of the particles while not forming an oxide layer that encases the particles.