Quenchant dengan konduktivitas termal tinggi dapat meningkatkan lajupendinginan, sehingga didapat hasil perlakuan panas dengan sifat mekanis yang lebihbaik. Salah satu cara meningkatkan konduktivitas termal adalah dengan membuatnanofluida. Pada penelitian ini, digunakan nanopartikel berupa Multi-walled CarbonNanotubes (MWCNT) as-received. Nanofluida berbasis CNT disintesis menggunakanmetode dua tahap. CNT dengan konsentrasi sebesar 0,1%, 0,3%, dan 0,5%didispersikan pada fluida dasar berupa air distilasi. Untuk meningkatkan stabilitasnanofluida, ditambahkan surfaktan Sodium Dodecyl Benzene Sulphonate (SDBS)sebanyak 3%, 5%, dan 7% serta dilakukan ultrasonikasi selama 15 menit. Nanofluidatersebut digunakan sebagai quenchant dengan lama imersi 4 menit untuk prosesperlakuan panas baja S45C dengan temperatur austenisasi sebesar 900˚C. Hasilpenelitian menunjukkan bahwa konduktivitas termal nanofluida meningkat seiringdengan penambahan konsentrasi CNT, kecuali pada sampel tanpa penambahansurfaktan. Seiring penambahan surfaktan, konduktivitas termal meningkat hinggamencapai kadar optimum dan kemudian menurun, kecuali pada sampel denganpenambahan surfaktan sebanyak 3%. Nilai kekerasan baja S45C hasil quenching tidakdipengaruhi secara linear oleh konduktivitas termal quenchant.
Quenchant with high thermal conductivity could increase the cooling rate;hence heat treatment results with better mechanical properties are obtained. Onemethod to increase the thermal conductivity is by creating nanofluids. In this study,Multi-walled Carbon Nanotubes (MWCNT) as-received were used as nanoparticles.The CNT-based nanofluids were synthesized using the two-step method. CNTs withconcentrations of 0.1%, 0.3%, and 0.5% were dispersed to the base fluid, distilledwater. To increase the stability of the nanofluids, Sodium Dodecyl Benzene Sulphonate(SDBS) surfactants as much as 3%, 5%, and 7% were added; further, ultrasonicationwas carried out for 15 minutes. The nanofluids were used as quenchants with animmersion time of 4 minutes for the heat treatment process of S45C steel with anaustenitizing temperature of 900˚C. The results showed that the thermal conductivity ofnanofluids increased with the addition of CNT concentration, except for sampleswithout the addition of surfactants. On the other side, as more surfactants were added,the thermal conductivity increased until it reached the optimum level and thendecreased, except for samples with 3% surfactant. The hardness values of quenchedS45C steels are not linearly affected by the thermal conductivity of the quenchants. |
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