Mechanical Properties and Adhesion of Oxide Films Formed on Pure Titanium at High Temperature Corrosive Environments

Abstract

The oxide films formed on metallic surfaces at high temperature corrosive environments often act as diffusive barriers of oxygen to protect the metal from corrosion. However, damage to metallic materials is possibly accelerated by mechanical fractures and spalling of the oxide films, caused by such as collisions of fly ash and thermal stresses of the oxide films. Investigations on mechanical properties and adhesion of oxide films formed on metal surfaces at high temperature corrosive environments lead to estimating the life time of materials and to searching high temperature corrosion prevention techniques. Both high temperature corrosion and round particle impact tests were performed on pure titanium coupon specimens. Both a particle impact method and an exfoliation/fracture model of oxide films were very useful to examine elastic modulus, fracture stresses and strains, and adhesive stresses of oxide films formed on pure titanium at high temperature environments. The spalling of the titanium oxide films was experimentally reproduced by the temperature decrement calculated by the elastic modulus and the adhesive stress obtained in this study, and by the thermal expansion coefficients of titanium and titanium oxide. These mechanical properties obtained in this study were, therefore, proved to be valid.