Influence of Cooling Rate on Hardness and Machinability in Low-Carbon Steel WAAM

Document Type : Original Article

Authors

Mohammad Ebadi Tavallaei ¹

Kiana Arteshyar ²

Mahdi Mazloom Farsibaf ²

Farhad kolahan ²

Sadegh Elhami ²

¹ Mechanical Engineering Department, Ferdowsi University of Mashhad, Mashhad, Razavi Khorasan, Iran.

² Mechanical Engineering Department, Ferdowsi University of Mashhad, Mashhad, Razavi Khorasan, Iran

10.22067/jacsm.2026.93580.1329

Abstract

Wire Arc Additive Manufacturing (WAAM), especially in its Metal Active Gas (MAG) form, has emerged as a promising technique for fabricating large and complex metal components. In this study, walls were built on ST37 steel substrates using ER70S-6 filler wire, with voltage and travel speed varied between 20–22 V and 100–200 mm/min, respectively. Hardness measurements revealed a gradient from 213.5 HV at the edges to 137.4 HV at the center, attributed to differing cooling rates. Rapid edge cooling led to fine-grained microstructures, while slower cooling in the center resulted in coarser grains. Optical microscopy confirmed a hypoeutectoid microstructure of ferrite and pearlite. Despite minor porosity, the produced walls showed a yield strength of 490 MPa—significantly higher than the 400 MPa of the base metal. These findings demonstrate the mechanical effectiveness of the WAAM-MAG process. However, the non-uniform hardness can impact machining performance, making tool selection and parameter optimization essential. Accurate assessment of hardness gradients is crucial for improving post-processing and achieving consistent component quality.

Keywords

Wire Arc Additive Manufacturing

Hardness Distribution

Microstructural and Mechanical Analysis

Low-carbon steel alloy

ER70S-6 wire filler

Subjects

• Design and manufacture

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