Characterizing Oxide Inclusions in Welded Lean Duplex Stainless Steels and Their Influence on Impact Toughness

Area of Science:

• Materials Science
• Metallurgy
• Welding Engineering

Background:

• Newly developed 2101 lean duplex stainless steel is susceptible to oxide inclusions in welded zones.
• These oxide inclusions can potentially affect the mechanical properties, specifically impact toughness, of the welded metal.

Purpose of the Study:

• To assess the correlation between oxide inclusions and mechanical impact toughness in flux-cored arc welded 2101 lean duplex stainless steel.
• To characterize the nature and composition of oxide inclusions present in the welded metal.

Main Methods:

• Flux-cored arc welding (E2209T1-1 filler metal) was used to create welded metal zones.
• Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) were employed for detailed investigation.

Main Results:

• Spherical oxide inclusions, rich in titanium, silicon, and manganese, were identified within the ferrite matrix, near intragranular austenite.
• The observed oxides included amorphous Ti- and Si-rich oxides, MnO (cubic), and TiO2 (orthorhombic/tetragonal).
• No strong correlation was found between the type of oxide inclusions and the absorbed energy (impact toughness).

Conclusions:

• The presence of various oxide inclusions in the welded metal did not significantly impair mechanical impact toughness.
• No crack initiation was observed originating from these oxide inclusions, suggesting they do not act as critical flaws.