Microstructure and high temperature mechanical properties of the new cladding steel of 15Cr-15Ni-Ti-Y

Abstract

• A new cladding 15-15Ti-Y steel with fine and dispersed particles was manufactured via casting. • With 0.25 wt% Y addition, uniform distribution of particles was achieved and the size of e particles was 10–155 nm. • Compared with the conventional 15-15Ti alloy, YS of the new 15-15Ti-Y alloy is 1.8 times at 600 °C. Titanium stabilized austenitic stainless steel of 15Cr-15Ni-Ti (15-15Ti) is a primary choice for fast reactor cladding material due to its high ductility, high oxidation and corrosion resistance. In order to further improve the irradiation resistance and operating temperature, it is necessary to produce the second phase reinforced 15-15Ti steels. In this work, three 50 kg 15-15Ti-Y ingots were prepared by casting method assisted by oxygen carrier and the Y additions were 0, 0.25 wt% and 0.5 wt%, respectively. Microstructure observation indicated the optimal addition of Y was 0.25 wt%. As Y addition reached 0.5 wt%, nonuniform microstructure with streamline distribution of Y-O-bearing particles and TiC appeared. In the 15-15Ti-25Y steel, average size of the Y-O-bearing particles were 10–155 nm and the number density of second particles was 9.40 × 10 20 m −3 . Furthermore, the uniform distribution of these fine particles remarkably improved the strength at high temperatures. Specifically, the yield strength of the 15-15Ti-25Y steel was 1.8 times than that of the Y-free steel at 600 °C.