Investigasi Mekanisme Pembentukan Fase Sigma Pada Kegagalan Pengelasan Super Duplex Stainless Steel UNS S32750 Dengan Pendekatan Root Cause Analysis

Warman, Mulya (2023) Investigasi Mekanisme Pembentukan Fase Sigma Pada Kegagalan Pengelasan Super Duplex Stainless Steel UNS S32750 Dengan Pendekatan Root Cause Analysis. Masters thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Super duplex stainless steel (SDSS) memiliki ketahanan korosi yang sangat baik hingga 20 tahun di lingkungan korosif. Namun, proses pengelasan dengan parameter yang tidak terkontrol rentan terbentuknya fase sigma yang menyebabkan umur layanannya berkurang. Sehingga studi pengaruh parameter pengelasan sangat penting untuk menentukan root cause terbentuknya fase sigma. Pada studi ini, material UNS S32750 telah diteliti variabel pengelasan yang meliputi proses plasma cutting pada preparasi bevel, root gap, heat input, suhu inter-pass dan overlap stop/start terhadap terbentuknya fase sigma. Pengujian material menggunakan optical emission spectrometry (OES). Uji makro untuk mengamati penampang cross-section. Struktur mikro dianalisis secara metalografi dengan perbesaran 400x dengan mikroskop optik dilanjutkan karakterisasi scanning electron microscope (SEM) dan emission dispersive spectroscopy (EDS). Efek variabel pengelasan diuji korosi menggunakan metode ASTM G48 dan ASTM G5 dan hardness ditentukan dengan microhardness Vickers. Hasil penelitian menunjukan preparasi bevel, material yang digunakan serta penerapan heat input dan suhu inter-pass tidak menunjukkan adanya fase sigma. Sedangkan nilai hardness menunjukkan lebih tinggi pada lokasi HAZ karena struktur butiran yang lebih halus. Kemudian root gap menyempit dan titik stop/start ditemukan memiliki fase sigma dan korosi pitting.
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Super duplex stainless steel (SDSS) has excellent corrosion resistance for up to 20 years in corrosive environments. However, a welding process with uncontrolled parameters is susceptible to a sigma phase, which leads to a reduction in its service life. So, the study of the effect of welding parameters is very critical to determine the root cause of the sigma phase formation. In this study, UNS S32750 material examined welding variables which included the plasma cutting process in the preparation of the bevel, root gap, heat input, inter-pass temperature, and stop/start overlap for the formation of the sigma phase. Material testing using optical emission spectrometry (OES). To observe cross-sections, perform a macro test. The microstructure was analyzed metallographically at 400x magnification with an optical microscope followed by scanning electron microscopy (SEM) and dispersive emission spectroscopy (EDS) characterization. The welding effect was tested for corrosion by ASTM G48 and ASTM G5 methods and the hardness was determined by Vickers microhardness. The results showed that the preparation of the bevel, the material employed, and the application of heat input and inter-pass temperature did not show any sigma phase. Meanwhile, the hardness value is higher at the HAZ location because of the finer grain structure. Then the root gap narrowed and the stop/start point had a sigma phase and pitting corrosion.

Item Type:	Thesis (Masters)
Uncontrolled Keywords:	Fase sigma, root gap, super duplex stainless steels, struktur mikro, root cause analysis Sigma phase, root gap, super duplex stainless steels, microstructure, root cause analysis
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:	Mulya Warman
Date Deposited:	03 Aug 2023 05:28
Last Modified:	03 Aug 2023 05:28
URI:	http://repository.its.ac.id/id/eprint/102002

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