Exfoliation and Fracture Behavior of Oxide Films Formed on Titanium and Its Alloy in High Temperature Environments

Abstract

It is very difficult to obtain mechanical properties of oxide films formed on a material in high temperature environments despite its importance of estimating material degradation caused by such as thermal stress. Corrosion/oxidation tests were conducted for pure titanium and titanium alloy in high temperature corrosive environments of wet air and water vapor with hydrogen chloride at temperatures from 673 K to 973 K to look into basic behavior of degradation and the growth of titanium oxide films. It was found that oxide films were usually formed on the specimen surface and the growth was accelerated by the corrosiveness of the environment. In order to examine mechanical properties and exfoliation of corrosion products or oxide films formed on titanium and its alloy, tests of single particle impact on the specimen surface with a glass bead were performed in high temperature corrosive environments. The piling-up surfaces around impact craters were formed and plastically strained. The oxide film formed on the metal surface was detached in a wide range of the circumference and fractured a little far from the rim of the crater. Then fracture and exfoliation stress of the oxide film were estimated by the calculation of impact energy and fractured and detached areas. It was found that both the fracture and exfoliation stress of the oxide films were different depending on the corrosive environment and chemical composition of titanium alloy.

Evaluation of Mechanical Properties for Chromium Carbide Coatings at High Temperature

“…It is difficult to investigate the foregoing properties under high-temperature circumstances because of the difficulties in setting up measurement systems in a high-temperature environment. Apart from the mechanical properties of coating materials, the adhesive and mechanical properties of protective oxides and coating films formed on substrate metals have been investigated [6,7] at high temperatures, using impact from a spherical particle. Dynamic hardness and crack generation were investigated by the same impact method and analyses [8].…”

Dynamic Mechanical Properties of Oxide Films Formed on Metallic Surfaces as Measured Using a Tribological Approach at High Temperature

“…For the present study, we used an impact method to measure the dynamic mechanical properties of oxide films formed on the surfaces of mild steel, titanium, and its alloy [10,11], as examples of practical plant component materials. In this paper, we compare and discuss the mechanical and adhesive properties of oxide films on various metallic materials in high-temperature corrosive environments, elucidating the validity of the impact method experimentally.…”