Microstructure characteristic of TIG and laser welding of Super Duplex Stainless Steel

By: Thoria Sharef , Maryem Morghem , Nuri Bhieh

Authority of Natural Sciences and Technology Research – Welding Center – Libya

Issue: Vol 21 |First Issue | 2015

article language: English

Abstract:

This study focuses on the behavior of super duplex stainless steel (EN 1.4410, UNS S32750) subjected to laser beam welding and activated Tungsten Inert Gas (TIG) welding using silica powder flux. The study aimed to evaluate the effect of these welding techniques on the microstructure and hardness of weld joints of 3mm thick plates. The results revealed that both techniques play an important role in obtaining satisfactory mechanical properties. Using nitrogen as a shielding gas with argon in laser welding resulted in an improved microstructure of the weld metal compared to TIG welding, leading to a change in the standard ratios of ferrite and austenite phases in the weld metal and heat-affected zone (HAZ). In laser welding, the very high cooling rates resulted in an improper ferrite/austenite balance due to decreased austenite content and subsequently increased ferrite content compared to the base metal. Hardness measurements showed an increase in the hardness of the HAZ for both processes, with slightly higher hardness in the case of laser welding.