Microstructural Analysis of Partially Diluted Zones in Dissimilar Cladding: EBSD Insights on AWS E 309L Alloy via MIG Process in Single- and Double-Layer Depositions on ASTM A36 Steel

The surge in deep and ultra-deep water oil exploration in Brazil, particularly in the pre-salt layer, necessitates the advancement of materials and engineering components to meet sectoral challenges. To enhance the longevity and corrosion resistance of pipelines and structures, welded cladding of stainless alloys onto structural steels has been deployed. However, dissimilar welding often leads to the formation of Partially Diluted Zones (PDZ), marked by discontinuous, high-hardness regions at the interface. This study employs Electron Microscopy via Backscattered Electron Diffraction (EBSD) to characterize these zones, addressing limitations in conventional metallographic techniques. By cladding ASTM A36 steel test plates with AWS E 309L (309L stainless steel) through automated MIG welding, metallurgical-mechanical properties were assessed using Field Emission Scanning Electron Microscopy (FEG-SEM), EBSD, SEM-EDS, and Vickers Microhardness. The Heat-Affected Zone (HAZ) displayed low hardness, while the PDZ exhibited varied morphologies with significant concentrations of iron, chromium, and nickel, accompanied by elevated microhardness and a characteristic martensitic microstructure. In comparison between single and double-layer depositions, the latter substantially reduced hardness in the PDZ and HAZ. This study provides critical insights into the microstructural attributes of welded cladding, offering valuable guidance for optimizing materials in deepwater applications.

Keywords:
309L Stainless Steel; Dissimilar Welding; PDZ; EBSD