Development of a Portable Device for Thermoelectrical Power Measurement—Application to the Inspection of Duplex Stainless Steel Components

Some cast components of the primary loop of French Pressurized Water Reactors are made of cast duplex stainless steels. The mechanical characteristics of these components, working in the temperature range from 285°C to 325°C, may be altered by thermal aging : the hardness of the materials increases whereas its toughness decreases with aging time and temperature. The metallurgical explanation of this phenomena is the unmixing of the ferritic Fe-Cr-Ni solid solution by spinodal decomposition and the precipitation of intermetallic G-phase particles rich in nickel and silicium [1]

Microstructural evolution of α or β quenched zirconium alloys during isothermal agings, between 20 °C and 750 °C

In Zircaloy and zirconium alloys, after quench from the upper limit of the α domain a small quantity of iron, chromium or nickel remains in solid solution and then precipitates during further isothermal aging. This precipitation is studied between 450°C and 600°C, using thermoelectric power (TEP) and resistivity measurements. It is shown that precipitation kinetic is strongly reduced by the presence of oxygen and tin. After quench from the β domain (1030°C) five stages of evolution are detected by TEP measurements in Zircaloy-4, the more important being : - a low temperature evolution (<400°C) attributed to local atomic rearrangements - the precipitation of iron and chromium initially dissolved. The amplitude of TEP variation shows that β quench do not permit to allow larger amount of iron and chromium in solution tha for α quench - the recrystallization of the initial martensitic structure

Development of a Portable Device for Thermoelectrical Power Measurement—Application to the Inspection of Duplex Stainless Steel Components

Some cast components of the primary loop of French Pressurized Water Reactors are made of cast duplex stainless steels. The mechanical characteristics of these components, working in the temperature range from 285°C to 325°C, may be altered by thermal aging : the hardness of the materials increases whereas its toughness decreases with aging time and temperature. The metallurgical explanation of this phenomena is the unmixing of the ferritic Fe-Cr-Ni solid solution by spinodal decomposition and the precipitation of intermetallic G-phase particles rich in nickel and silicium [1].</p