The dissimilar metal welds in the most of the reactors are connections between low alloy steel parts and stainless steel piping. There is a high possibility of primary water stress corrosion cracking (PWSCC) damage attributed to residual stress caused by the difference in material properties in the dissimilar metal weld joints. A number of accidents such as leakage of radioactive coolant due to PWSCC have been reported around the world, posing a great threat to nuclear safety. The objective of this study is to develop a technology that can fundamentally remove dissimilar metal welds by replacing the existing dissimilar metal parts with the functionally graded material (FGM) manufactured by metal 3D printing consisting of low alloy steel and austenitic stainless steel. A powder production, mixing ratio calculation, and metal 3D printing were performed to fabricate the low alloy steel-stainless steel FGM, and microstructure analysis, mechanical properties, and coefficient of thermal expansion (CTE) measurement of the FGM were performed. As a result, it is observed that CTE tended to increase as the austenite content increased in FGM. The gradual change of coefficient of thermal expansion in a FGM showed that the additive manufacturing using 3D printing was effective for preventing an abrupt change in thermal expansion properties throughout their layers.

Celem nr 1 artykułu jest odnotowanie i teoretyczne wyjaśnienie trzech kluczowych faktów dotyczących wzrostu gospodarczego w skali globalnej w ostatnich dwóch wiekach. Te fakty to gwałtowne przyśpieszenie wzrostu gospodarczego w niewielkiej części gospodarki światowej około 2 wieki temu, duża stabilność trendu tego wzrostu w tej części w okresie tych dwóch wieków oraz silne zróżnicowanie tempa wzrostu w tym okresie w krajach słabo rozwiniętych. Celem numer 2 jest sformułowanie w świetle tych wyjaśnień prognozy wzrostu gospodarczego, też w skali globalnej, w najbliższych dwóch wiekach.