Effect of SMAW manufacturing process in high-cycle fatigue of AISI 304 base metal using AISI 308L filler metal

The shielded metal arc welding (SMAW) process is commonly used in many applications due to its high versatility in the manufacturing of industrial parts, components and assemblies. This paper is about the effect SMAW process on the high-cycle fatigue of austenitic stainless steel AISI 304 using AISI 308L filler metal. Two different parameters (factors) of the manufacturing process were evaluated: type of electrode coating and heat input in the welding process. Three different electrode coating were compared: E308L-15, E308L-16 and E318L-16 Premium. Additionally, three different heat inputs levels were used in the welding process for each electrode covering (“low”, “medium” and “high”). For this welding application, cold rolled plates 300 mm length, 76.2 mm wide, 6.4 mm thick of AISI/SAE 304 were used as base material, making up V-groove type joints on them. After welding, microstructure characterization using optical and scanning electron microscopy; chemical analysis composition; HRB hardness test; tensile test and ferrite number (FN) of the welded joints were evaluated. Fatigue tests were conducted in the INSTRON 8872 machine. To analyze the fatigue results, Quantitative Analysis Accelerated Life Testing was used, wherewith Smax-N graphs were plotted among all the experimental factors (as a factorial experiment). It was found that solidification of weld shows dendrite growth with both ventricular and lathy morphologies. The E308L-15 electrode deposits have better resistance to high cycle axial fatigue than the other electrode deposits. Furthermore, we found that the high-cycle fatigue resistance of the deposits is enhanced at lower heat inputs of welding process and greater FN. Material failures were localized among the weld deposit, through the dendrite orientation on microstructure that also led the growth of the crack.