Analysis of Component Depth Profiles at the Interface of Ti6242 Alloy and SiC, SiN Coatings after High Temperature Oxidation in Air

Abstract

We have analyzed the interfacial elemental depth profile evolution after high temperature isothermal oxidation of SixCy and SixNy protective coatings deposited by dynamic ion mixing on a Ti6242 alloy (Ti-6Al-2Sn-4Zr-2Mo). Isothermal oxidation tests have been carried out at 600°C during 100 hours in air. We have observed a non-monotonic depth distribution of zirconium in GDOES and SIMS depth profiles after oxidation of SiC/Ti6242 and SiN/Ti6242 and we propose a kinetic model based on rate equations for analyzing the results. It is shown by modeling that a non-monotonic depth profile of zirconium occurs because zirconium from the Ti6242 alloy forms a zirconium oxide compound. As a result, the atomic concentration of zirconium decreases at the interface which induces a diffusion flux of zirconium from the bulk to the interface. This process leads to the increase of the total amount of zirconium at the film interface and thus formation of a non-monotonic depth profile.