THE EFFECT OF IRON ADDITION ON HYDROGEN ABSORPTION TO TITANIUM

摘要

Ti and its alloys have been employed in a lot of applications as structural materials in the chemical and the petroleum industries because of attractive mechanical properties and extremely good corrosion resistance. However there is a problem that absorbing hydrogen sometimes produce titanium hydride and induce embrittlement to Ti. Moreover, it is known that the hydrogen absorption to Ti is promoted when Fe species are contained in Ti substrate or in aqueous solution as an impurity. In this study, the effect of Fe addition on hydrogen absorption to Ti has been investigated. Pure Ti and Ti-1.5 at% Fe alloy (denoted as 1.5Fe) were prepared in a laboratory scale arc-melting furnace. Button-shaped ingot was hot-rolled at 1170 K. Hydrogen was charged to the specimen in an aqueous solution of pH 1 containing 0.6 kmol m~(-3) Cl~- at 353 K. A charging potential varied from -1.65 to -0.85 V_(Ag/AgCl) until a charge density of 10 MC m~(-2). The amount of hydrogen absorbing in the specimen was measured using thermal desorption gas spectroscopy (TDS). Both Ti and 1.5Fe provided two peak temperatures in hydrogen desorption rate depending on temperature of the specimen (TDS profile). The peak rate at higher temperature was constant as the applied potential changed. On the other hand, that at lower temperature increased when the applied potential shifted to positive. The amount of hydrogen absorption in both Ti and 1.5Fe increased, while the rate of hydrogen absorption decreased as the applied potential shifted to positive. There was also seen an increase in the rate of hydrogen adsorption when Fe was added to Ti.