Tensile and Fatigue Characteristics on Thermal Aged Welds of Stainless Steels for Heat Exchangers at High Temperature

Purpose: This study aims to determine the most suitable material for heat exchangers by analyzing the tensile and fatigue strengths of different types of stainless steel, i.e., AISI 310S, AISI 316L, and AISI 347 after welding and aging at both room and high temperatures. BRMethods: Tensile and fatigue tests were performed on three types of stainless steel for heat exchangers using samples aged at 800℃ for 1000 hours and samples that were welded and aged at both room temperature and 800℃. The microstructures of the base material and aged samples were observed using an optical microscope and SEM. The fatigue tests were conducted using a stress ratio of 0.1 and a stress constant test; the fracture surface was then observed using SEM.BRResults: Chromium carbides tend to precipitate more in aged stainless steel samples than in the base material. It was found that AISI 316L stainless steel has the best elongation and fatigue strength at room temperature and 800℃.BRConclusion: In terms of aged and welded samples, AISI 316L stainless steel has the highest elongation and endurance limit. In particular, it has the smallest amount of chromium carbide precipitation at 800℃. In conclusion, it is determined to be an excellent heat exchanger material in terms of weldability, formability, and durability.