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Presentation of new developments in welding technology in the form of a master's thesis.

Title: Influence of welding parameters and surface finish on the corrosion resistance of Inconel 625 coatings deposited by the PTA-P process
Author: Thayse Francielle Peralta

Date: March 4, 2026, 3:30 PM
Advisor: Prof. Carlos Enrique Niño Bohórquez, Dr. Eng.
Co-advisor: Prof. Mateus Barancelli Schwedersky, Dr. Eng.

Abstract:

Ni–Cr–Mo alloy-based coatings, such as Inconel 625, are widely used as protective barriers on components exposed to aggressive environments containing chlorides, due to their high corrosion resistance. In this study, Inconel 625 coatings produced by the powder-fed Plasma Transferred Arc (PTA-P) process were evaluated regarding the influence of welding parameters and surface condition on bead geometry, microstructure, and corrosion behavior. The coatings were deposited using different combinations of welding current and speed and analyzed in both as-deposited and ground surface conditions. Geometric dilution ranged approximately from 4.9% to 16.7%, reflecting the balance between welding energy and the amount of material effectively deposited per unit length. The observed microstructures were typical of rapidly solidified Ni–Cr–Mo alloys, featuring dendritic morphology and variations in refinement, fusion continuity, and interdendritic segregation of Nb and Mo as a function of welding conditions. The as-deposited surfaces exhibited geometric irregularities characteristic of the PTA-P process, mainly associated with pass overlap and the presence of partially melted particles. These surface heterogeneities resulted in greater dispersion of the electrochemical response during potentiodynamic polarization tests in a 3.5% NaCl solution. After grinding, a more stable and reproducible electrochemical behavior was observed, with a reduction of approximately two orders of magnitude in the corrosion current density, indicating a decrease in the uniform corrosion rate. The results show that, although welding parameters influence bead geometry and coating microstructure, the surface condition plays a central role in the corrosion kinetics of PTA-P applied Inconel 625 coatings in a chloride medium. Corrosion performance was governed by the interaction between welding parameters, bead geometry, microstructure, and surface finish, without the dominance of a single isolated variable.