Influence of yttrium ion-implantation on oxidation kinetics of Co-40Cr alloy and property of oxide/substrate interface

Abstract

The isothermal and cyclic oxidizing kinetics of Co-40Cr alloy and its yttrium ion-implanted samples were studied at 1000°C in air by thermal-gravity analysis (TGA). Scanning electronic microscopy (SEM) was used to examine the Cr₂O₃ oxide film’s morphology after oxidation. Secondary ion mass spectroscopy (SIMS) method was used to examine the binding energy change of chromium caused by yttrium doping. Acoustic emission (AE) method was used in situ to monitor the cracking and spalling of oxide films formed on both samples during oxidizing and subsequent air-cooling stages. It is found that yttrium implantation remarkably reduces the isothermal oxidizing rate of Co-40Cr and improves the anti-cracking and anti-spalling properties of Cr₂O₃ oxide film. The reasons for the improvements are mainly that implanted yttrium reduces the grain size of Cr₂O₃ oxide, increases the high temperature plasticity of oxide film, and remarkably reduces the number and size of Cr₂O₃/Co-40Cr interfacial defects.

Keywords

interface / element binding energy / oxidation / acoustic emission

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