Pengaruh Variasi Konsentrasi Polymer Quenchant PAG Terhadap Kekerasan Dan Kedalaman Pengerasan Baja AISI L6

Gaviota, Alvito Kafi (2026) Pengaruh Variasi Konsentrasi Polymer Quenchant PAG Terhadap Kekerasan Dan Kedalaman Pengerasan Baja AISI L6. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Pengendalian laju pendinginan (cooling rate) pada proses perlakuan panas baja AISI L6 sangat krusial untuk mengoptimalkan sifat mekanis dan mencegah cacat material. Penelitian ini bertujuan untuk mengetahui pengaruh variasi konsentrasi polymer quenchant Polyalkylene Glycol (PAG) terhadap distribusi kekerasan dari tepi menuju titik pusat penampang, serta pengaruhnya terhadap kedalaman pengerasan. Proses quenching memanfaatkan prinsip inverse solubility PAG, di mana larutan akan membentuk lapisan selimut polimer (vapor blanket) saat bersentuhan dengan baja bersuhu tinggi. Hasil pengujian menunjukkan bahwa lapisan polimer ini memberikan efek penundaan pendinginan (delayed quenching) yang menggeser kurva Continuous Cooling Transformation (CCT) baja AISI L6 memotong zona transformasi menengah.Akibatnya, fasa mikro yang mendominasi adalah bainit dengan nilai kekerasan 600 HVN, berbeda dengan pendinginan air murni yang menghasilkan fresh martensite. Analisis kedalaman pengerasan mengungkap terjadinya fenomena inverse hardening, di mana kekerasan bagian inti material justru lebih tinggi dibandingkan area tepinya. Anomali ini terjadi karena area permukaan terisolasi lebih lama oleh selimut polimer, sementara bagian inti yang mengalami akumulasi pelepasan panas laten (latent heat) mendapatkan percepatan pendinginan secara mendadak saat selimut di permukaan terkoyak oleh arus agitasi. Berdasarkan variasi konsentrasi, penggunaan PAG 5% menghasilkan lapisan yang terlalu tipis sehingga memicu thermal shock yang mengunci kisi kristal dan menyisakan fasa lunak Austenit Sisa (Retained Austenite) di permukaan. Sebaliknya, konsentrasi PAG 15% membentuk insulator tebal layaknya oli yang menurunkan nilai kekerasan secara drastis ke rentang 31.93 – 52.49 HRC akibat pendinginan yang terlampau lambat. Disimpulkan bahwa konsentrasi PAG 10% dengan sistem agitasi merupakan parameter paling optimal untuk mengekstraksi panas secara seimbang, mencegah thermal shock, dan menghasilkan struktur bainitik dengan distribusi kekerasan yang paling homogen dari tepi hingga ke inti material. ====================================================================================================================================
Controlling the cooling rate in the heat treatment process of AISI L6 steel is highly crucial to optimize mechanical properties and prevent material defects. This study aims to investigate the effect of concentration variations of Polyalkylene Glycol (PAG) polymer quenchant on the hardness distribution from the edge to the center of the cross-section, as well as its effect on the depth of hardening. The quenching process utilizes the inverse solubility principle of PAG, where the solution forms a protective polymer film (vapor blanket) upon contact with the high-temperature steel. The experimental results indicate that this polymer layer provides a delayed quenching effect, which shifts the continuous cooling transformation (CCT) curve of the AISI L6 steel to intersect the intermediate transformation zone. Consequently, the dominant microstructural phase obtained is bainite with a hardness value of approximately 600 HVN, in contrast to pure water quenching which yields fresh martensite. Hardenability analysis revealed the occurrence of an inverse hardening phenomenon, where the hardness at the core of the material is higher than that at its surface edge. This anomaly occurs because the surface area is insulated longer by the polymer film, while the core area undergoing accumulated latent heat release experiences a sudden cooling acceleration when the surface polymer blanket is abruptly ruptured by agitation currents. Based on concentration variations, the 5% PAG solution produces an excessively thin polymer layer, triggering thermal shock that locks the crystal lattice and leaves a soft retained austenite phase at the surface. Conversely, the 15% PAG concentration forms a thick, oil-like insulating layer, drastically reducing the hardness value to a range of 31.93 – 52.49 HRC due to an excessively slow cooling rate. It is concluded that a 10% PAG concentration combined with an agitation system is the most optimal parameter to achieve balanced heat extraction, prevent thermal shock, and produce a bainitic structure with the most homogeneous hardness distribution from the edge to the core of the material

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Baja AISI L6, Quenching, Polymer Quenchant, Polyalkylene Glycol (PAG), Kekerasan, Struktur Mikro, Inverse Hardening, AISI L6, Quenching, Polymer Quenchant, Polyalkylene Glycol (PAG), Hardness Distribution, , Microstructure, Inverse Hardening
Subjects:	Q Science T Technology > TN Mining engineering. Metallurgy > TN752.I5 Steel--Heat treatment T Technology > TN Mining engineering. Metallurgy > TN752.Q4 Metals--Quenching
Divisions:	Faculty of Industrial Technology and Systems Engineering (INDSYS) > Mechanical Engineering > 21201-(S1) Undergraduate Thesis
Depositing User:	Alvito Kafi Gaviota
Date Deposited:	04 Aug 2026 07:43
Last Modified:	04 Aug 2026 07:43
URI:	http://repository.its.ac.id/id/eprint/143543

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