Session: 03-05 Metals: Dissimilar Materials

Paper Number: 93918

93918 - Effect of Secondary Austenite on Fracture Toughness Properties of Wire Arc Additively Manufactured Duplex Stainless Steels 

Duplex stainless steels (DSS) are among the preferred materials in down- and up-stream oil and gas operations due to their superior corrosion and mechanical properties. The fraction and morphology of secondary austenite in DSS are critical in terms of their corrosion resistance and toughness. Additive manufacturing techniques are emerging into options for the manufacturing of DSS assemblies that are conventionally manufactured using casting and forging. Such conventional material processes have proven procedures that provide proper phase balance in DSS. However, investigating additive manufacturing of DSS is still vital to have a good understanding of the influence of process variables. For this purpose, DSS grade 2209 coupons were fabricated using a wire arc additive manufacturing (WAAM) process with a 6-axis robotic manipulator using wire arc speeds of 7 and 14 (mm/s), an interlayer temperature of 100°C, and shielding gases of industrially pure Argon and Argon with oxygen and nitrogen additions. 

The coupons were then examined by optical and field emission scanning electron microscopy, X-ray diffraction, and electron backscattered diffraction. The fracture toughness properties of materials constitute an important input for damage tolerant design and fitness for service assessments. In this regard, elastic-plastic fracture toughness values of the as-built DSS coupons were determined, as well, and compared to assess the performance of building strategies, such as shielding atmosphere and cooling rates. In the present work, it was observed that the shielding gas composition determined significantly the fraction and morphology of secondary austenite, which is transformed due to successive thermal cycles during wire arc additive manufacturing, rather than the reconstructive transformation process of primary austenite. Post-test analyses revealed that secondary austenite, on the one hand, provided barriers and retarded the crack extension in laboratory air. On the other hand, chromium and molybdenum depletion in the neighborhood of secondary austenite precipitates motivated unstable crack extension under chloride attack.

Presenting Author: Koray Yurtisik Ion Industrial Metallurgy Research and Development Inc.

Presenting Author Biography: After receiving my master’s degree in Metallurgical and Materials Engineering, I worked as a non-destructive inspection engineer and 3rd party surveyor at various industrial manufacturing and construction sites worldwide. Meanwhile I received my International Welding Engineering diploma. Following my contributions in a fitness-for-service engineering assessment of a petrochemical plant as an engineer, I was employed by a leading corporate finance firm as an advisor on oil & gas industry in Turkey. In the following years, as the chief welding engineer at one of Turkey’s top three largest EPC contractors, I was responsible for the welding activities of industrial and civil infrastructures in both its fabrication halls and field sites. Then I was appointed as engineer in charge for the welding coordination of other companies in the group. Simultaneously, I started to give lectures in the welding engineering program at the university. Besides giving lectures, I was assigned to manage R&D and industrial projects at Welding Technology and Non-destructive Testing Research / Application Centre of the university where I completed my PhD studies and received the degree as well. Thanks to number of projects I was involved in, I have had the opportunity to utilize my metallurgical and welding engineering knowledge in the aerospace industry for the last couple of years. I am a founder of Ion Industrial Metallurgy R&D where we develop novel materials and processing technologies for aerospace and power generation industries. Ion IM R&D owns the only independent Nadcap material testing laboratory in Turkey.

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