HIGH TEMPERATURE OXIDATION PROCESS AFFECTED BY SHOT-PEENING: APPLICATION TO PURE ZR AND TI

An evaluation of the shot-peening effects on the oxidation rate of Zr and Ti between 350 degrees C and 650 degrees C for 100h is presented. It is shown that the oxidation rate can substantially be decreased by shot-peening at high temperatures (T > 500 degrees C) while at lower temperatures the effect is opposite. An investigation of the various factors that can play a role on the oxidation behaviour was realized in order to separate their influence. It was shown that the pollution of the surface that can eventually occur during the shot-peening process is not responsible for the oxidation rate decrease. It was proposed that, at temperatures giving mainly a bulk diffusion of the O2- ions within the metal volume, the slowing of the oxidation rate could be explained by the mechanical stress.