Microstructural Evolution, Ferrite Content, and Grain Size Study in the Coalescence of High Nitrogen Austenitic Stainless Steel Thick Plates Using Cold Metal Transfer Welding Process

• Published in: Journal of materials engineering and performance 2024-05, Vol.33 (9), p.4422-4434
• Main Authors: Koli, Yashwant, Roy, Jayanta Ghosh, Yuvaraj, N., Vipin, Vedabouriswaran, G.
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Corrosion and Coatings; Engineering Design; Materials Science; Quality Control; Reliability; Safety and Risk; Technical Article; Tribology
• ISSN: 1059-9495; 1544-1024
• DOI: 10.1007/s11665-023-08247-z

Nickel-free high nitrogen stainless steel (HNS) is having great demand in cryogenic industries, biomedical instruments and various medical implants and stents. This is also being used in electronic industries and defense like armored battlefield vehicles. In this paper, efforts have been put to prepare butt welded 5 mm thickness HNS by spattering free highly efficient cold metal transfer (CMT) process using multi-pass welding to study the material characterization, microstructural evolution, ferrite content and furthermore residual stresses. The addition of nitrogen is found to be economical with better mechanical results. Results show that nitrogen plays a significant role in enhancing mechanical properties. Low heat input welding effectively welds HNS with substantial tensile strength. Due to the development of martensite, the higher heat input welded sample (710.40 J/mm) has the maximum tensile strength, microhardness, joint efficiency, and compressive residual stress with the lowest ductility. Due to heat accumulation between multiple passes and high ferrite concentration at the center of the weld bead, the microhardness value of the weld bead is decreased. Grain size is 36.49 µm at the junction of weld bead (WB) and heat-affected zone (HAZ), 31.87 µm at HAZ, 23.74 µm at junction of HAZ and base metal (BM), and 15.61 m at BM, with microhardness of 317.76, 336.72, 347.28, and 362.05 HV, respectively. Grain size evolution from base metal to weld bead shows a significant impact on the mechanical properties.