e-ISSN 2231-8542
ISSN 1511-3701

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Effects of Two Cycle Heat Treatment on the Microstructure and Hardness of Ductile Iron

Mohd Faizul Idham, Bulan Abdullah and Khalissah Muhammad Yusof

Pertanika Journal of Tropical Agricultural Science, Volume 25, Issue S, March 2017

Keywords: Ductile iron, hardness, heat treatment, microhardness

Published on: 05 Dec 2017

Austempering is one of the trendiest heat treatment processes to promote the strength and toughness of ductile iron. However, such practice is complex because it involves using aqueous solutions as quenchant (salt bath solution). This study was conducted to analyse the heat treatment of the combination processes of annealing-austenitising and evaluate the correlation between microstructure constituent and hardness of the ductile iron. Ductile iron samples in form of double cylinder was produced by conventional CO2 sand casting method. The new heat treatment process was started by annealed at 873 K for 1.8 ks before being oil quenched. Subsequently, the samples were austenitised at austenitising temperatures 1123 K, 1173 K and 1223 K for 3.6 ks respectively before being immediately oil quenched to room temperature. A series of microstructure analysis tests, including optical microscopy and X-ray diffraction (XRD) was applied. Vickers microhardness tester was used to measure the hardness for each microstructure constituent. The results showed that ductile iron matrix transforms to martensitic during heat treatment of annealing-austenitising combination processes, which in turn contributes to increasing microhardness of martensite and the bulk hardness of ductile iron

ISSN 1511-3701

e-ISSN 2231-8542

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