Fe-Based Filler Material Forming Austenite-Covered Packet Lath Martensite for Gas Tungsten Arc Welding of 9% Ni Steel

초록

Fe-based filler material with a composition of Fe-20Ni-5Co-2.5Mn-0.2C is developed for welding 9% Ni steel. To ensure high weldability through compositional similarity, the composition of the Fe-based filler material is designed based on that of 9% Ni steel. The filler material has elements such as Ni, Mn, Co, and C to enhance its compatibility with the 9% Ni steel. The Fe-based filler material is designed to control the martensite formation temperature, resulting in the appearance of the martensite-austenite dual phase during rapid cooling. The weld joint shows a distinct microstructure characterized by the presence of austenite-covered packet lath martensite. The mechanical properties of the weld joint are investigated via Vickers harness and tensile tests at 25 and -163 degrees C. In comparison to 9% Ni steel, the weld joint prepared using the Fe-based filler material exhibits yield and tensile strengths that are approximate to 5.5% higher. Additionally, the tensile fracture of the specimen occurs exclusively within the base metal, without any involvement of the weld metal or heat-affected zone. Further, the fracture surface is observed. In the findings of this study, the applicability of the Fe-based filler material for welding 9% Ni steel is demonstrated. Herein, a novel Fe-based filler for welding 9% Ni steel is presented. The weld joint using the Fe-based filler material forms a unique microstructure with austenite-covered lath martensite. The results demonstrate over a 5.5% improvement in yield and tensile strengths for welds using the Fe-based material compared to 9% Ni steel.image (c) 2023 WILEY-VCH GmbH

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