Abstract Overlay welding with stainless steels has gained attention in several sectors of industry by increasing the mechanical and electrochemical properties of surfaces, in order to obtain them using lower cost substrates. However, the control of welding parameters can become complex due to the multiple control variables, being of interest to obtain deposits with greater productivity. In this context, the objective of this paper is to analyze the effect of the heat input on weld overlays of austenitic stainless steel 316L-Si obtained by the GMAW process, to determine the best welding conditions. For this, a Design of Experiments was implemented to analyze the response variables, which include heat input, reinforcement, width, dilution and hardness of the weld metal. The models were considered significant, presenting R2>0.9 for all responses, based on a 95% confidence limit. Surface graphs indicated influence of welding speed or/and voltage for all responses, in addition to the results demonstrating optimal parameters for overlays such as high ratio between reinforcement and width (0.631), and low dilution values (8.81%). The microstructural analysis indicated the presence of residual γ-austenite and δ-ferrite in all samples, and also the formation of peninsulas and islands, added to defects such as voids, for some weld deposits.

Abstract Aluminum alloys of 7xxx series have excellent characteristics and mechanical properties, being widely used in primary aircraft structures. However, the welding of these alloys by conventional arc welding processes results in an excessive mechanical resistance degradation and increasing in residual stress level. In this context, Friction Stir Welding (FSW) process has received attention in recent years mainly because it does not reach the materials melting point during the process. This work aims to evaluate the influence of the tool rotation and welding speed on microstructure and mechanical properties of AA 7075-T651 aluminum alloy welded joints by FSW process. Therefore, four welded joints obtained with different welding and tool rotation speed were subjected to tensile and microhardness tests. The microstructures of the welded joints were evaluated through analysis by optical microscopy and Scanning Electron Microscopy (SEM). The retreating side of the welded joints showed a higher occurrence of microstructural welding defects. Welded joints with yield strength (YS) 50% higher than those of base metal and with ultimate tensile strength up to 380 MPa were achieved.