Investigation of Long and Short Term Irradiation Hardening of P91 and P92 Ferritic/Martensitic Steels

Abstract

The aim of the study was to determine the effect of proton irradiation at room temperature on ferritic/martensitic P91 and P92 steels, in particular on their hardness. In addition, SRIM programme was used to identify the proton penetration depth. The study has found that the hardness of the unirradiated P92 steel is higher than that of unirradiated P91 steel, since P92 steel contains tungsten, which produces higher level of solid solution hardening. P91 and P92 steel samples were irradiated using 1.9-MeV protons to the fluence of 1.3510 17 ion/cm 2 . It was found that Vickers hardness test values increased for both P91 and P92 steels at 0.2 kg loads. For high proton irradiation (long irradiation period) the fluence was 1.10110 18 ion/cm 2 (about ten times higher than at the low proton irradiation). With growth of irradiation fluence, the number of displacements per atom (dpa) went up from 0.043 dpa (for low irradiation) to 0.18 dpa (for high irradiation) and the hardness of steels that were under investigation increased. P91 and P92 steel samples after long irradiation were heat treated for one hour at 700 o C in a vacuum furnace. The study identified that while the chemical composition of P91 and P92 steel were almost identical, irradiated P92 steel requires twice the heat treatment to reduce its hardness to a basic value, as compared with P91 steel samples.Целью данного исследования было определение влияния облучения протонами при комнатной температуре на ферритномартенситные стали Р91 и Р92, в частности, на их твёрдость. Кроме того, для изучения глубины внедрения протонов в стали была использована вычислительная программа SRIM. Обнаружено, что необлучённая сталь Р92 твёрже, чем необлучённая сталь Р91. Сталь Р92 содержит вольфрам, который способствует упрочнению твёрдых растворов. Образцы сталей Р91 и Р92 были кратковременно облучены протонами энергией 1,9 МэВ до флюенса 1,35·10 17 ион/см 2 . Под нагрузкой 200 г их твёрдость по Виккерсу увеличилась. Затем аналогичные образцы были подвергнуты приблизительно в 10 раз более длительному облучению до флюенса 1,101·10 18 ион/см 2 . С увеличением продолжительности облучения увеличилось число смещений на атом с 0,043 до 0,18 млн -1 и увеличилась твёрдость образцов. После более длительного облучения образцы исследуемых сталей были подвергнуты термообработке -помещены на один час в вакуумную печь при температуре 700 ºС. Исследование показало, что, хотя химический состав исследованных сталей почти идентичен, термообработка облучённой стали Р92 для снижения её твёрдости до исходного уровня требует вдвое большего времени, чем термообработка образцов стали Р91.Ключевые слова: программа SRIM, сканирующий электронный микроскоп, смещение на атом, сталь Р91, сталь Р92.

The Use of the Stopping and Range of Ions in Matter Code for Calculation of Damage in Three Different Types of Steel

“…It provides a pressure boundary in which the core is contained and performs as an essential safety barrier between fission products from the core and the surroundings. It also supports the core and all its components and directs coolant flow [1][2][3]. It is generally formed from tempered and quenched ferritic/bainitic steel that has good toughness.…”

Monte Carlo calculation of absorbed dose under MeV proton irradiation

“…This is because the crosssection values would change as the proton through the specimen losing energy. This is the advantage of a computer simulation as now the heavy computations can be easily processed [26][27][28][29][30][31][32]. In this work, simulation was carried out to predict radioactivity.…”

A molecular dynamics calculation to cascade damage processes

“…It is used to calculate radiation damage calculation method exposure unit known as displacement per atom (dpa). Thus, dpa has been used as a standard measure for computing proton-neutron induced radiation damage production from different radiation sources [11][12][13][14][15]. Molecular dynamics simulation of processes in metals have been studied by many research groups including temperature dependence of the processes of cascade damage [16][17][18].…”