The safety and longevity of small modular reactors are affected by reactor pressure vessels,which are complex integral components made of SA508 Gr.3 low-alloy steel.In this study,the impacts of heat accumulation on th...The safety and longevity of small modular reactors are affected by reactor pressure vessels,which are complex integral components made of SA508 Gr.3 low-alloy steel.In this study,the impacts of heat accumulation on the microstructural and mechanical characteristics(tensile properties and Charpy V-notched impact energy)of SA508 Gr.3 steel fabricated using laser powder-directed energy deposition were investigated.Rectangular samples were prepared using long raster and short raster scanning strate-gies for changing heat buildup,and the mechanical tests were conducted depending on build direction.The time-temperature profile measured at a fixed point in the long raster sample showed a lower max-imum temperature and a higher cooling rate,indicating lower heat accumulation compared to that of the short raster sample.In each build direction,the yield strength of the long raster sample was 45.8%-60.5%higher and its ductile-brittle transition temperature was 76.8-103.8℃ lower than that of the short raster sample.Additionally,compared to conventionally made samples and without requiring heat treat-ment,the long raster sample exhibited over a 45%increase in yield strength and a 22.7℃ reduction in the ductile-brittle transition temperature.The superior combination in long raster samples is induced by smaller effective grain size,smaller cementite,and a higher pre-existing dislocation density.The re-sults emphasize the importance of controlling heat accumulation throughout the additive manufacturing process and provide valuable insights into the use of additive manufacturing for manufacturing reactor pressure vessels in the nuclear industry.展开更多
基金supported by the National Research Foundation of the Ministry of Science and ICT(MSIT)of the Republic of Korea(grant No.2022M3H4A1A02076759)also supported financially by the Korea Atomic Energy Research Institute R&D program(Con-tract No.524590-24).
文摘The safety and longevity of small modular reactors are affected by reactor pressure vessels,which are complex integral components made of SA508 Gr.3 low-alloy steel.In this study,the impacts of heat accumulation on the microstructural and mechanical characteristics(tensile properties and Charpy V-notched impact energy)of SA508 Gr.3 steel fabricated using laser powder-directed energy deposition were investigated.Rectangular samples were prepared using long raster and short raster scanning strate-gies for changing heat buildup,and the mechanical tests were conducted depending on build direction.The time-temperature profile measured at a fixed point in the long raster sample showed a lower max-imum temperature and a higher cooling rate,indicating lower heat accumulation compared to that of the short raster sample.In each build direction,the yield strength of the long raster sample was 45.8%-60.5%higher and its ductile-brittle transition temperature was 76.8-103.8℃ lower than that of the short raster sample.Additionally,compared to conventionally made samples and without requiring heat treat-ment,the long raster sample exhibited over a 45%increase in yield strength and a 22.7℃ reduction in the ductile-brittle transition temperature.The superior combination in long raster samples is induced by smaller effective grain size,smaller cementite,and a higher pre-existing dislocation density.The re-sults emphasize the importance of controlling heat accumulation throughout the additive manufacturing process and provide valuable insights into the use of additive manufacturing for manufacturing reactor pressure vessels in the nuclear industry.
