International Journal of Iron & Steel Society of Iran

International Journal of Iron & Steel Society of Iran

Microstructural and Mechanical Properties of a Medium-Silicon Low-Alloy Steel under Quenching and Partitioning Heat Treatment: A Comparative Study with Step Quenching Process

Document Type : Research Paper

Authors
A. Khajesarvi
S. S. Ghasemi Banadkouki
Department of Mining and Metallurgical Engineering, Yazd University, Yazd, Iran
10.22034/ijissi.2026.2070586.1328
Abstract
This study aims to investigate the mechanical behavior of a medium-silicon lowalloy steel subjected to quenching and partitioning (QP) heat treatment and to compare it with that of step quenching (SQ). Microstructural observations were carried out using field-emission scanning electron microscopy (FE-SEM) with electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Furthermore, mechanical tests including hardness, tensile, and impact tests, as well as phase analysis by X-ray diffraction (XRD), were employed. The results revealed that the product of ultimate tensile strength and total elongation, a reliable criterion for evaluating advanced high-strength steels, increased from 2.4 to 10.2GPa·% in QP samples at 280°C, compared with SQ samples at 720°C. The improvement in the mechanical properties of QP specimens is attributed to a micro-composite microstructure containing carbide-free tempered martensite (CFTM), fresh martensite (FM), carbide-free bainite (CFB), and retained austenite (RA). This differs from the ferrite–martensite dual-phase microstructures of SQ specimens. Moreover, the Charpy impact energy of SQ specimens was 3.5J, while the QP specimens exhibited the highest impact energy absorption with 5.5J.
Keywords
Medium-Silicon Low-Alloy Steel
Quenching and Partitioning (QP)
Step Quenching (SQ)
Mechanical Properties
Subjects
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