Mechanical Properties and Microstructure of TIG and ATIG Welded 316L Austenitic Stainless Steel with Multi-Components Flux Optimization Using Mixing Design Method and Particle Swarm Optimization (PSO).

Abdeljlil Chihaoui Hedhibi,Hussein Alrobei,Abousoufiane Ouis,Rachid Djoudjou,Mohamed M Z Ahmed,Kamel Touileb

doi:10.3390/ma14237139

Abstract

In this study, the effects of pseudo-ternary oxides on mechanical properties and microstructure of 316L stainless steel tungsten inert gas (TIG) and activating tungsten inert gas (ATIG) welded joints were investigated. The novelty in this work is introducing a metaheuristic technique called the particle swarm optimization (PSO) method to develop a mathematical model of the ultimate tensile strength (UTS) in terms of proportions of oxides flux. A constrained optimization algorithm available in Matlab 2020 optimization toolbox is used to find the optimal percentages of the selected powders that provide the maximum UTS. The study indicates that the optimal composition of flux was: 32% Cr2O3, 43% ZrO2, 8% Si2O, and 17% CaF2. The UTS was 571 MPa for conventional TIG weld and rose to 600 MPa for the optimal ATIG flux. The obtained result of hardness for the optimal ATIG was 176 HV against 175 HV for conventional TIG weld. The energy absorbed in the weld zone during the impact test was 267 J/cm2 for the optimal ATIG weld and slightly higher than that of conventional TIG weld 256 J/cm2. Fracture surface examined by scanning electron microscope (SEM) shows ductile fracture for ATIG weld with small and multiple dimples in comparison for TIG weld. Moreover, the depth of optimized flux is greater than that of TIG weld by two times. The ratio D/W was improved by 3.13 times. Energy dispersive spectroscopy (EDS) analysis shows traces of the sulfur element in the TIG weld zone.

Highlights

Austenitic stainless steels are the most common stainless steel
Tungsten Inert Gas (TIG) welding is a widespread process in industries, but a limited thickness can be joined in a single pass with this process
Is 565 MPa, which was obtained for the sample welded with ZrO2 flux, followed by the sample welded with Cr2 O3 flux with 559 MPa and, by the sample welded with TiO2 flux with 542 MPa

Summary

Introduction

Austenitic stainless steels are the most common stainless steel. They are used in many fields as oil, shipbuilding, machinery, and marine applications. They are characterized by good strength, high toughness, and excellent corrosion resistance. Fusion welding is the most popular method to join workpieces in many industrial applications. Tungsten Inert Gas (TIG) welding is a widespread process in industries, but a limited thickness can be joined in a single pass with this process. Materials thickness greater than 3 mm requires multiple passes to achieve full penetration weld; the productivity of the process is reduced. The activated tungsten inert gas (ATIG) technic is a variant of

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Conclusion