Karakterisasi Mikrostruktur Dan Sifat Mekanik Paduan Centrifugally Cast 25Cr-35Ni+Nb Steam Reformer Tube Setelah Beroperasi 130.000 Jam

Salam, Ken Daewood (2026) Karakterisasi Mikrostruktur Dan Sifat Mekanik Paduan Centrifugally Cast 25Cr-35Ni+Nb Steam Reformer Tube Setelah Beroperasi 130.000 Jam. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Industri petrokimia sangat bergantung pada unit steam methane reformer (SMR) untuk memproduksi hidrogen, dengan salah satu komponen utamanya berupa steam reformer tube yang beroperasi pada temperatur tinggi dalam jangka waktu yang lama. Kondisi operasi tersebut menyebabkan evolusi mikrostruktur secara bertahap yang dapat memengaruhi sifat mekanik material serta mengurangi keandalan komponen. Penelitian ini bertujuan mengkarakterisasi mikrostruktur dan sifat mekanik paduan centrifugally cast 25Cr–35Ni+Nb (HP40Nb) pada steam reformer tube setelah beroperasi selama 130.000 jam, serta menganalisis hubungan antara perubahan mikrostruktur dengan degradasi sifat mekaniknya. Berdasarkan hasil termografi, Section A berada pada rentang temperatur operasi 632–720°C, sedangkan Section C berada pada rentang temperatur 720–792°C, sehingga analisis difokuskan pada section tersebut. Karakterisasi mikrostruktur dilakukan menggunakan Scanning Electron Microscopy–Energy Dispersive Spectroscopy (SEM–EDS) untuk mengidentifikasi morfologi karbida dan komposisi fasa, serta analisis fraksi area melalui segmentasi citra SEM dengan perangkat lunak Microstructural Image Processing, Analysis, and Recognition (MIPAR) untuk mengevaluasi distribusi kuantitatif matriks dan karbida. Selanjutnya, pengujian kekerasan, tarik, dan impak dilakukan untuk mengevaluasi perubahan ketahanan terhadap deformasi plastis, kekuatan tarik, dan ketangguhan material. Hasil penelitian menunjukkan bahwa Section C (720–792°C) mengalami evolusi mikrostruktur yang lebih signifikan dibandingkan Section A (632–720°C), ditandai dengan koalesensi karbida, peningkatan fraksi area Cr₂₃C₆ dari 13,55% menjadi 23,41%, peningkatan fraksi area NbC dari 2,43% menjadi 4,97%, serta penurunan fraksi area matriks dari 86,45% menjadi 76,60%. Analisis SEM–EDS juga mengidentifikasi keberadaan fasa G (Ni₁₆Nb₆Si₇) sebagai indikasi transformasi sebagian NbC akibat paparan temperatur tinggi jangka panjang. Perubahan mikrostruktur tersebut berkorelasi dengan penurunan nilai kekerasan dari 166,67 HV0,5 menjadi 161,83 HV0,5 dan kekuatan tarik maksimum dari 469,56 ± 1,04 MPa menjadi 346,94 ± 5,09 MPa, sementara elongasi dan energi impak meningkat. Hasil ini menunjukkan bahwa degradasi sifat mekanik ditentukan oleh peningkatan fraksi area karbida, perubahan morfologi, coarsening, serta transformasi NbC menjadi fasa G yang menurunkan efektivitas mekanisme precipitation strengthening. Oleh karena itu, hasil karakterisasi mikrostruktur dan pengujian sifat mekanik ini dapat dijadikan sebagai acuan data (baseline) dalam mengevaluasi tingkat degradasi material, sehingga memberikan informasi pendukung yang relevan untuk pelaksanaan condition assessment pada komponen steam reformer tube.
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The petrochemical industry relies heavily on steam methane reformer (SMR) units to produce hydrogen, with one of its primary components being the steam reformer tube, which operates at high temperatures for extended periods. These operating conditions cause gradual microstructural evolution that can affect the mechanical properties of the material, reduce creep resistance, and decrease component reliability. This study aims to characterize the microstructure and mechanical properties of a centrifugally cast 25Cr–35Ni+Nb (HP40Nb) alloy in a steam reformer tube after 130,000 hours of operation, and to analyze the relationship between microstructural changes and the degradation of its mechanical properties. Based on thermography results, Section A was within the operating temperature range of 632–720°C, while Section C was within the 720–792°C range; therefore, the analysis focused on these sections. Microstructural characterization was conducted using Scanning Electron Microscopy–Energy Dispersive Spectroscopy (SEM–EDS) to identify carbide morphology and phase composition, along with area fraction analysis via SEM image segmentation using Microstructural Image Processing, Analysis, and Recognition (MIPAR) software to evaluate the quantitative distribution of the matrix and carbides. Furthermore, hardness, tensile, and impact tests were performed to evaluate changes in resistance to plastic deformation, tensile strength, and material toughness. The results showed that Section C (720–792°C) experienced more significant microstructural evolution compared to Section A (632–720°C), characterized by carbide coalescence, an increase in the Cr₂₃C₆ area fraction from 13.55% to 23.41%, an increase in the NbC area fraction from 2.43% to 4.97%, and a decrease in the matrix area fraction from 86.45% to 76.60%. SEM–EDS analysis also identified the presence of the G phase (Ni₁₆Nb₆Si₇), indicating a partial transformation of NbC due to long-term high-temperature exposure. These microstructural changes correlated with a decrease in hardness from 166.67 HV0.5 to 158.67 HV0.5 and maximum tensile strength from 469.56 ± 1.04 MPa to 346.94 ± 5.09 MPa, while elongation and impact energy increased. These results indicate that the degradation of mechanical properties is determined by the increase in carbide area fraction, morphological changes, distribution, coarsening, and the transformation of NbC into the G phase, which reduces the effectiveness of precipitation strengthening and solid solution strengthening mechanisms. Therefore, the results of this microstructural characterization and mechanical testing can serve as baseline data for evaluating the extent of material degradation, providing relevant supplementary information for conducting condition assessments on steam reformer tube components.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Steam reformer tube, karbida, mikrostruktur, fraksi area, sifat mekanik Steam reformer tube, carbide, microstructure, area fraction, mechanical properties.
Subjects:	T Technology > TJ Mechanical engineering and machinery T Technology > TJ Mechanical engineering and machinery > TJ263 Heat exchangers
Divisions:	Faculty of Industrial Technology and Systems Engineering (INDSYS) > Mechanical Engineering > 21201-(S1) Undergraduate Thesis
Depositing User:	Ken Daewood Salam Daewood Salam
Date Deposited:	04 Aug 2026 09:27
Last Modified:	04 Aug 2026 09:27
URI:	http://repository.its.ac.id/id/eprint/143605

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