Pengaruh Variasi Suhu Tempering Terhadap Kerentanan Stress Corrosion Cracking Pada Material AISI 4340 Menggunakan Metode U-BEND Dan Immersion Test

Zurqoni, Mohammad Nabriz (2026) Pengaruh Variasi Suhu Tempering Terhadap Kerentanan Stress Corrosion Cracking Pada Material AISI 4340 Menggunakan Metode U-BEND Dan Immersion Test. Masters thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Rantai Submerged Scraper Conveyor (SSC) pada Pembangkit Listrik Tenaga Uap (PLTU) beroperasi dalam lingkungan basah, bersuhu tinggi, dan mengandung ion klorida, serta mengalami tegangan tarik statis, sehingga rentan terhadap degradasi material dan kegagalan akibat stress corrosion cracking (SCC). Salah satu upaya mitigasi SCC yang dapat diterapkan adalah perlakuan panas tempering untuk memodifikasi mikrostruktur dan menurunkan tegangan sisa material. Penelitian ini bertujuan untuk menganalisis pengaruh variasi suhu tempering terhadap mikrostruktur, sifat mekanik, laju korosi, dan kerentanan SCC pada baja AISI 4340. Material uji terdiri atas material existing rantai SSC (Material A dan Material B) serta material AISI 4340 baru (Material C). Seluruh spesimen mengalami proses quenching yang dilanjutkan dengan tempering pada suhu 500 °C, 600 °C, dan 700 °C. Pengujian meliputi pengamatan mikrostruktur, uji mikrohardness Vickers, U-bend test untuk pemberian tegangan tarik, serta immersion test dalam larutan NaCl 3,5 wt% selama 336 jam untuk evaluasi perilaku korosi dan potensi SCC. Hasil penelitian menunjukkan bahwa peningkatan suhu tempering menyebabkan terurainya struktur tempered martensite menjadi campuran ferrite dan cementite, disertai dengan pertumbuhan ukuran karbida. Perubahan mikrostruktur tersebut meningkatkan keuletan material namun menurunkan nilai kekerasan. Nilai mikrohardness menurun dari kisaran 463–487 HV pada suhu tempering 500 °C menjadi 322–348 HV pada suhu 700 °C. Laju korosi juga menunjukkan tren penurunan seiring peningkatan suhu tempering, dengan nilai berada pada rentang 0,063–0,179 mm/tahun. Material existing menunjukkan laju korosi yang lebih tinggi dibandingkan material baru pada seluruh variasi suhu tempering. Hingga akhir perendaman 336 jam, terbentuk produk korosi berupa pit dan indikasi awal pit-to-crack tanpa ditemukannya retak yang berkembang. Hal ini menunjukkan bahwa tempering pada suhu tinggi efektif menurunkan laju korosi dan menekan propagasi awal SCC pada baja AISI 4340.
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Submerged Scraper Conveyor (SSC) chains in steam power plants operate in wet, high-temperature environments containing chloride ions and are subject to static tensile stress, making them susceptible to material degradation and failure due to stress corrosion cracking (SCC). One SCC mitigation effort that can be applied is tempering heat treatment, which modifies the microstructure and reduces residual stress in the material. This study aims to analyze the effect of tempering temperature variations on the microstructure, mechanical properties, corrosion rate, and SCC susceptibility of AISI 4340 steel. The test materials consisted of existing SSC chain materials (Materials A and B) and a new AISI 4340 material (Material C). All specimens underwent a quenching process followed by tempering at temperatures of 500 °C, 600 °C, and 700 °C. The tests included microstructure observation, Vickers microhardness testing, U-bend testing for tensile stress, and immersion testing in a 3.5 wt% NaCl solution for 336 hours to evaluate corrosion behavior and SCC potential. The results showed that increasing the tempering temperature caused the decomposition of the tempered martensite structure into a mixture of ferrite and cementite, accompanied by carbide growth. These microstructural changes increased the ductility of the material but decreased its hardness. The microhardness value decreased from a range of 463–487 HV at a tempering temperature of 500 °C to 322–348 HV at a temperature of 700 °C. The corrosion rate also showed a downward trend as the tempering temperature increased, with values ranging from 0.063 to 0.179 mm/year. The existing material showed a higher corrosion rate than the new material across all tempering temperature variations. By the end of the 336-hour immersion, corrosion products in the form of pits and early indications of pit-to-crack were formed without any developing cracks being found. This indicates that high-temperature tempering effectively reduces the corrosion rate and suppresses the initial propagation of SCC in AISI 4340 steel.

Item Type:	Thesis (Masters)
Uncontrolled Keywords:	AISI 4340, tempering, Stress Corrosion Cracking, U-bend Test, Immersion Test, Corrosion Rate
Subjects:	T Technology > TN Mining engineering. Metallurgy > TN690 Metallography. Physical metallurgy
Divisions:	Faculty of Industrial Technology and Systems Engineering (INDSYS) > Mechanical Engineering > 21101-(S2) Master Thesis
Depositing User:	Mohammad Nabriz Zurqoni
Date Deposited:	28 Jan 2026 03:35
Last Modified:	28 Jan 2026 03:35
URI:	http://repository.its.ac.id/id/eprint/130654

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