Studi Pengaruh Weld Discoloration Terhadap Struktur Mikro, Sifat Mekanik & Korosi Pada Material Duplex UNS S32205 Untuk Aplikasi Marine Atmosphere

Lesmana, Dera (2023) Studi Pengaruh Weld Discoloration Terhadap Struktur Mikro, Sifat Mekanik & Korosi Pada Material Duplex UNS S32205 Untuk Aplikasi Marine Atmosphere. Masters thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Tesis ini menyelidiki secara komprehensif dampak weld dicoloration pada mikrostruktur, sifat mekanik, dan ketahanan korosi duplex stainless steel. Penelitian ini berfokus pada pemahaman hubungan antara variasi tingkat oksigen selama proses pengelasan dan pembentukan lapisan oksida termal yang dapat merusak lapisan pasif yang berfungsi sebagai pelindung. Empat parameter oxygen level spesifik dianalisis secara mendalam, yaitu <20 ppm, <90 ppm, <500 ppm, dan <900 ppm. Dengan menggunakan teknik Optical Emission Spectroscopy (OES) dan Scanning Electron Microscope-Energy Dispersive X-Ray (SEM-EDX), penelitian ini menunjukkan bahwa peningkatan oxygen level selama proses pengelasan berkorelasi dengan penurunan jumlah unsur kimia penting pada duplex stainless steel seperti molibdenum dan nitrogen yang disebabkan oleh fenomena transportasi seperti difusi, absorpsi, redeposisi, oksidasi, dan evaporasi. Hal ini berdampak pada pembentukan fase austenit sekunder yang memiliki sifat inferior dibandingkan dengan fase austenit primer pada duplex stainless steel. Selanjutnya, analisis ferit menunjukkan bahwa peningkatan tingkat oksigen dan heat input selama proses pengelasan menghasilkan jumlah ferit yang lebih tinggi. Namun, hasil pengujian kekerasan menunjukkan bahwa tidak ada perubahan yang signifikan pada sifat mekanik DSS. Dalam hal ketahanan korosi, pengujian korosi pitting menggunakan metode ASTM G48 method A selama 72 jam menunjukkan bahwa terjadi peningkatan laju korosi akibat adanya oksida termal pada permukaan DSS. Selain itu, pengujian potentiodinamik juga dilakukan untuk mempelajari parameter korosi seperti potensial korosi (Ecorr), potensial pitting (Epit), dan arus korosi (Icorr) guna mempelajari efek weld discoloration pada DSS dalam lingkungan marine atmosphere.
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This thesis provides a comprehensive investigation into the impact of weld discoloration on the microstructure, mechanical properties, and corrosion resistance of duplex stainless steel (DSS). The study focuses on understanding the relationship between variations in oxygen levels during the welding process and the formation of thermal oxide layers that can potentially damage the passive layer, which serves as a protective barrier. Four specific oxygen level parameters were analyzed in depth: <20 ppm, <90 ppm, <500 ppm, and <900 ppm. Utilizing techniques such as Optical Emission Spectroscopy (OES) and Scanning Electron Microscope-Energy Dispersive X-Ray (SEM-EDX), the research revealed that an increase in oxygen levels during the welding process correlates with a decrease in the amount of crucial chemical elements in duplex stainless steel, such as molybdenum and nitrogen. This decrease is attributed to transportation phenomena such as diffusion, absorption, redeposition, oxidation, and evaporation. This, in turn, affects the formation of secondary austenitic phases, which exhibit inferior properties compared to primary austenitic phases in duplex stainless steel. Furthermore, ferrite analysis indicated that an increase in oxygen levels and heat input during the welding process results in a higher amount of ferrite. However, hardness testing showed that there were no significant changes in the mechanical properties of DSS. In terms of corrosion resistance, pitting corrosion testing using the ASTM G48 method A over a period of 72 hours demonstrated that there was an increase in the rate of corrosion due to the presence of thermal oxides on the surface of DSS. Additionally, potentiodynamic testing was conducted to study corrosion parameters such as corrosion potential (Ecorr), pitting potential (Epit), and corrosion current (Icorr) to understand the effects of weld discoloration on DSS in a marine atmosphere environment.

Item Type:	Thesis (Masters)
Uncontrolled Keywords:	duplex stainless steel, weld discoloration, oxygen level, korosi
Subjects:	T Technology > TS Manufactures > TS227 Welding.
Divisions:	Faculty of Industrial Technology and Systems Engineering (INDSYS) > Material & Metallurgical Engineering > 27101-(S2) Master Thesis
Depositing User:	Dera Lesmana
Date Deposited:	09 Jan 2024 01:15
Last Modified:	09 Jan 2024 01:15
URI:	http://repository.its.ac.id/id/eprint/105411

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