Integritas Material Bilah Turbin Uap Panas Bumi Tingkat Terakhir: Perbandingan Jethete M152 dan Stainless Steel 17-4 PH

Munir, Muhammad Mishbahul (2026) Integritas Material Bilah Turbin Uap Panas Bumi Tingkat Terakhir: Perbandingan Jethete M152 dan Stainless Steel 17-4 PH. Masters thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Bilah turbin uap panas bumi tingkat terakhir beroperasi pada lingkungan yang kompleks berupa uap basah, pengotor korosif, tumbukan droplet, beban sentrifugal, serta eksitasi dinamis. Kondisi tersebut dapat menyebabkan korosi, keausan, erosi, perubahan distribusi massa dan kekakuan, serta pergeseran frekuensi alami yang meningkatkan risiko resonansi. Penelitian ini bertujuan membandingkan integritas material Jethete M152 dan stainless steel 17-4 PH berdasarkan karakteristik komposisi kimia, mikrostruktur, kekerasan, ketahanan korosi, ketahanan aus, dan stabilitas dinamis bilah terhadap peningkatan level erosi. Pendekatan penelitian mengintegrasikan pengujian Optical Emission Spectroscopy, metalografi, Vickers microhardness, korosi elektrokimia dalam larutan 1,5 wt% NaCl, pengujian keausan pin-on-disc, karakterisasi SEM–EDS, pengujian frekuensi alami menggunakan table shaker, dan simulasi modal menggunakan ANSYS. Hasil penelitian menunjukkan bahwa kedua material memiliki mikrostruktur martensitik, tetapi Jethete M152 memperlihatkan susunan lath martensite yang lebih rapat dan seragam. Komposisi kimia baik material Jethete M152 dan Stainless Steel 17-4 PH masih memenuhi standard material masing-masing. Kekerasan rata-rata Jethete M152 mencapai 361,8 HV1, lebih tinggi daripada 17-4 PH sebesar 288,8 HV1. Pada pengujian korosi, Jethete M152 menghasilkan laju korosi lebih rendah daripada Stainless Steel 17-4 PH yaitu sebesar 0,007519 mm/tahun, sedangkan 17-4 PH sebesar 0,039324 mm/tahun. Jethete M152 juga memiliki ketahanan aus lebih baik dengan specific wear rate sebesar 1,419 × 10⁻⁴ mm³/N·m, dibandingkan 17-4 PH sebesar 3,742 × 10⁻⁴ mm³/N·m. Pengamatan SEM menunjukkan mekanisme keausan yang melibatkan groove, deformasi elastis, adhesi, delaminasi, fracture ridge, dan pembentukan produk oksida. Peningkatan level erosi terbukti mengubah frekuensi alami bilah, terutama pada mode yang lebih tinggi. Frekuensi puncak keempat menurun dari 320,84 Hz pada bilah normal menjadi 278,99 Hz pada erosi level 3. Pergeseran tersebut dapat mendekatkan frekuensi alami terhadap harmonik operasi 3X dan 6X sehingga meningkatkan potensi resonansi. Secara keseluruhan, Jethete M152 memberikan keseimbangan integritas material yang lebih baik dibandingkan 17-4 PH
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Last-stage geothermal steam turbine blades operate in a complex environment involving wet steam, corrosive contaminants, droplet impact, centrifugal loading, and dynamic excitation. These conditions may lead to corrosion, wear, erosion, changes in mass and stiffness distribution, and shifts in natural frequencies, thereby increasing the risk of resonance. This study aims to compare the material integrity of Jethete M152 and 17-4 PH stainless steel based on their chemical composition, microstructure, hardness, corrosion resistance, wear resistance, and the dynamic stability of the blade under increasing erosion levels. The research approach integrates Optical Emission Spectroscopy, metallographic examination, Vickers microhardness testing, electrochemical corrosion testing in a 1.5 wt% NaCl solution, pin-on-disc wear testing, SEM–EDS characterization, natural frequency testing using a shaker table, and modal simulation using ANSYS. The results show that both materials exhibit martensitic microstructures; however, Jethete M152 demonstrates a denser and more uniform lath martensite arrangement. The chemical compositions of both Jethete M152 and 17-4 PH stainless steel comply with their respective material standards. The average hardness of Jethete M152 reaches 361.8 HV1, which is higher than that of 17-4 PH at 288.8 HV1. In the corrosion test, Jethete M152 exhibits a lower corrosion rate of 0.007519 mm/year, whereas 17-4 PH records a corrosion rate of 0.039324 mm/year. Jethete M152 also demonstrates superior wear resistance, with a specific wear rate of 1.419 × 10⁻⁴ mm³/N·m, compared with 3.742 × 10⁻⁴ mm³/N·m for 17-4 PH. SEM observations reveal wear mechanisms involving grooves, elastic deformation, adhesion, delamination, fracture ridges, and oxide product formation. Increasing erosion levels were found to alter the blade’s natural frequencies, particularly at higher vibration modes. The fourth peak frequency decreased from 320.84 Hz for the normal blade condition to 278.99 Hz at erosion level 3. This frequency shift may bring the blade’s natural frequency closer to the 3X and 6X operating harmonics, thereby increasing the potential for resonance. Overall, Jethete M152 provides a better balance of material integrity than 17-4 PH stainless steel

Item Type:	Thesis (Masters)
Uncontrolled Keywords:	Bilah turbin panas bumi, Jethete M152, 17-4 PH, integritas material, korosi, pin-on-disc, frekuensi alami, erosi. Geothermal turbine blade, Jethete M152, 17-4 PH, material integrity, corrosion, pin-on-disc, natural frequency, erosion
Subjects:	T Technology > TJ Mechanical engineering and machinery > TJ266 Turbines. Turbomachines (General)
Divisions:	Faculty of Industrial Technology and Systems Engineering (INDSYS) > Mechanical Engineering > 21101-(S2) Master Thesis
Depositing User:	Muhammad Mishbahul Munir
Date Deposited:	05 Aug 2026 03:17
Last Modified:	05 Aug 2026 03:17
URI:	http://repository.its.ac.id/id/eprint/143902

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