Avaliação da influência do processo e dos parâmetros de soldagem sobre a resistência à corrosão de revestimentos de aços inoxidáveis AWS e 308-L T1 aplicados em aços ASTM A36.

Abstract

This study aimed to evaluate the influence of parameters and welding processes variation on the geometric characteristics, microstructure, microhardness, residual stress levels and corrosion resistance of AWS E308L - T1 weld overlays. It was used a factorial experimental design at two levels to evaluate the influence of control factors over the width (L), reinforcement (r) and dilution D (%), varying the reference voltage (U), feed rate (Va) and welding speed (Vs). Was used for determination of residual stresses the X-ray diffraction technique, with a Cr-kα anode, with 10 steps. The metallurgical characterization of weld overlays was done by Vickers microhardness tests and optical micrographs. The specimens were tested for corrosion resistance by linear polarization technique in a solution of NaCl (0.1 M). The welds were performed in the flat position by SAW and FCAW processes with shielding gas (70-30 mixture of CO2 and Ar). The weld overlays applied by FCAW process presented lower dilution and larger widths than those applied by the SAW process. The average deposition efficiency of both processes was 86%. The microhardness values in FCAW process were smaller than those weld overlays applied by SAW process, as well as a smaller number of occurrences of partially diluted zones. The level of residual stress were compressive in their entirety , being the residual stress field of weld overlays applied by FCAW process less compressive than those observed in the SAW process. This resulted in low corrosion resistance of the weld overlays applied by FCAW process. Therefore, the levels of residual stresses were a decisive factor in the corrosion resistance behavior of these welds overlays.