High ductility – Good strength stainless steel alloys at the elevated temperature for nuclear reactors core

Abstract

Reactors materials are the backbone of reactor life extending and making it safer. Accordingly, unabated research continues for the improvement of nuclear reactor materials, especially the reactor core materials. Hence, in the present article, two developed tungsten/molybdenum stainless steel grades MoW1 (0.843 wt% of Mo and 1.801 wt% of W) and MoW2 (0.251 wt% of Mo and 2.433 wt% of W) were produced. AISI316 standard stainless steel was used as a base material. Microstructural features of the produced alloys were investigated using Schaeffler diagram, optical microscopy, SEM-EDS, and X-ray diffraction. The mechanical properties of the produced alloys were studied at room temperature RT and elevated temperatures of 300 and 500 °C. W addition by 1.801 wt% at the expense of Mo (MoW1 steel) strengthened yield strength YS and ultimate tensile strength UTS by 42.344% and 32.022% at room temperature compared to the standard stainless steel AISI316, while a high affinity was found between YS and UTS results for steel containing 2.433 wt% of W (MoW2) and the AISI316. On the other hand, the elongation El% of MoW1 decreased by 20.861% and MoW2 by 17.219% compared to the AISI316. At 300 and 500 °C, the MoW1 stainless steel alloy has higher YS (by 4.865% and 7.865%) and UTS (by 17.580% and 41.077%) than AISI316. While, MoW2 has slightly lower YS (by 7.568% and 3.371%) and higher UTS (by 10.046% and 36.261%) than AISI316. Both of MoW1 and MoW2 has much higher El% than AISI316 at both 300 and 500 °C. As a comparison between the developed stainless steel alloys MoW1 and MoW2 for both 300 and 500 °C, MoW1 gave better YS (by 13.450% and 11.628%), UTS (by 6.8465% and 3.534%), and El% (18.3024% and 18.037%) results than MoW2. Accordingly, depending on the distinctive mechanical properties of the developed MoW1 stainless steel alloy at 300 and 500 °C, it is a strong candidate as an appropriate material for high-temperature conditions of the nuclear reactors core.