Andoko, Poppy Puspitasari, Femiana Gapsari
Two-step austempering treatment has been carried out by heating FCD at an austenitising temperature of 900 °C for 60 minutes, then FCD has been quenched in 50% NaNO3 + 50% KNO3 salt solution at an austempering temperature of 260 °C with 5 minutes and 15 minutes holding time, finally, the FCD has been reheated for 60 minutes. It has caused an improved tensile strength with increasing holding time at 260 °C. The treatment with 15-minute holding time generated the highest tensile strength of 621.65 N/mm2, while the one with 5-minute holding time has yielded the lowest one of 548.15 N/mm2. The microstructure of material held for 5 minutes has consisted of an austenite matrix with a small amount of coarse-grained acicular ferrite matrix, whereas the treatment with 15 minute holding time has resulted in a drop in the amount of austenite matrix and an increase in the amount of fine-grained acicular ferrite matrix. A rise in the amount and fineness of acicular ferrite matrix has brought improved tensile strength and ductility. The material subjected to the treatment with 15 minute holding time had the greatest ductility of 12%. The raw material and the material with 5 minute holding time had brittle fracture since their fracture surface has been flat and occurred by cleavage. © 2019 Praise Worthy Prize S.r.l.-All rights reserved.
Department of Mechanical Engineering, Faculty of Engineering, State University of Malang, Semarang st. 5, Malang, 65145, East Java, Indonesia; Department of Mechanical Engineering, Faculty of Engineering, Brawijaya University, Veteran, Malang, 65145, East Java, Indonesia
