Effect of zirconium ion implantation on the viscoplastic behavior of thermally grown chromia scales on NiCr alloy

Well-controlled amounts of zirconium, ranging from 10¹⁵ to 10¹⁶ ions·cm⁻², were introduced into a NiCr model alloy by ion implantation. The implanted samples were oxidized in air at 1000°C for 3 hours to form a stable oxide scale. Subsequently, the samples underwent successive thermal jumps of 100°C toward lower temperatures, inducing additional compressive stress within the oxide. In situ synchrotron X-ray diffraction was employed to monitor stress relaxation during consecutive 3-hour ε)isothermal plateau. Modeling of the experimental data using the classical Norton viscoplastic model confirmed that stress relaxation in the oxide scale was governed by diffusion creep mechanisms.