Effect of Post-Weld Treatment on the Microstructure and Mechanical Properties of Austempered FeNiCr Steel Welded Joint

¹ Department of Metallurgical and Materials Engineering, University of Indonesia, Depok, Indonesia
² Research Centre for Metallurgy, National Research, and Innovation Agency, Tangerang Selatan, Indonesia

^* Corresponding author: winarto@metal.ui.ac.id

Abstract

This study investigated isothermally treated FeNiCr structural steel welded joints. The base metal contains various phases which are dominated by a mixture of bainite and martensite. Joining this steel can be challenging since it has high carbon equivalent values and high hardness. Shielded metal arc welding (SMAW) with austenitic stainless-steel electrodes is used to avoid cold cracking. After the welding process, the samples were subjected to three various post-weld temperatures: 425°C, 475°C, and 525°C. From the tensile test results, the tensile strength of welded joint shows an increase as the temperatures increase. The highest value is reached for a joint sample which treated at 525°C, with a tensile strength of 680 MPa. Conversely, the highest elongation is obtained by the 425°C post-treated sample, which is 14%. The microstructure in the weld metal (WM) area shows a formation of δ-ferrite, whereas the HAZ and BM areas show the presence of bainite and martensite tempered phases with various plate densities, plate size, and plate shapes depending on its post-treatment temperatures, which then affect the value of the hardness.