The susceptibility to corrosion of Inconel 718 weldments after double aging heat treatment was studied by the use of potentiodynamic tests. Plates of 3 mm thick were homogenized at 1080 °C during 1 hour and air cooled, then subjected to a solution process at 980 °C during 1 hour and air cooled. The double aging heat treatment was; (1) aging at 720 °C during 8h and oven cooled at 55 °C/h, and (2) aging at 620 °C during 8h and air cooled at room temperature. After heat treatment, the plates were welded by using gas tungsten arc welding process with low and high heat input. The base metal (BM) and the weldments were analyzed by optical microscopy (OM), scanning electron microscopy (SEM) and X-Ray diffraction (XRD). The potentiodynamic tests were carried out in a 3.5% NaCl for the welded samples. The results show that, as the heat input increases, the corrosion rate increases in the weldments. This behavior can be attributed to the microsegregation of Nb and Mo, resulting in a Fe dilution into the weld pool.

The microstructural evolution of the nickel-base superalloy Inconel 718 after exposition at 750°C for different holding times (10 min–1,000 h) was characterized and correlated with the Eddy current (EC) technique. The results showed that electrical conductivity increases with aging time. This behavior was associated with the precipitation and coarsening of the metastable γ″ phase and its transformation into the detrimental δ phase after 100 h. EC nondestructive evaluation was correlated with X-ray diffraction patterns in terms of the precipitation and growth of secondary carbides that were observed in the scanning electron microscope. Vickers microhardness values were also in agreement with microstructural changes and EC measurements, as the maximum hardened condition can be associated with the precipitation of secondary phases before the transformation of the γ″ phase into the δ phase.

Ferritic stainless steels are widely used in transportation industry due to their exceptional performance regarding mechanical and corrosion properties. However, after a welding process, joints feature the sensitizing phenomenon because of the heat exchange from the torch affecting mechanical properties and corrosion resistance. This work describes the behavior firstly of mechanical properties of weld joints of ferritic stainless steel as base material without and with filler material (AISI 308L) by gas tungsten arc welding (GTAW). Operating parameters such as arc voltage, welding currrent, welding speed, feed speed, shielding gas flow were evaluated. Secondly, samples of weld joints were coated by flame spraying of composite particles in order to reduce the weight loss induced by corrosion in a salt spray (fog) apparatus. Changes induced from GTAW on the heat affected zone and Thermal Spraying on corrosion resistance, were monitored by optical and scanning electron microscopy, microhardness and longitudinal tensile testing. Results show that GTAW helps to control the size and the microstructure of heat affected zone improving simultaneously the mechanical properties. Meanwhile, welded joints covered by composite coatings feature a lower damage provided that the ceramic phase has been homogeneously dispersed.

Por medio del estudio por elemento finito se obtuvieron las isotermas generadas por el proceso de soldadura en la aleación de aluminio 6061-T6 empleando el programa ANSYS (plataforma APDL). Aunado a este estudio se aplicó un modelo matemático (para placa delgada) que rige el comportamiento de una fuente de calor en movimiento. Los resultados analíticos y por simulación numérica mostraron que el ancho máximo de la isoterma al cual ocurre el mayor sobre envejecimiento fue aproximadamente 10 mm a partir del centro del cordón de soldadura, sin embargo, de manera general los resultados analíticos no presentaron una correlación aceptable con los simulados.