The fractography and mechanical behaviour of fatigue crack propagation in the heat-affected zone (HAZ) of AISI 4140 steel welded using the shielded metal arc process was analysed. Different austenitic grain size was obtained by normalizing performed at 1200 °C for 5 and 10 hours after welding. Three point bending fatigue tests on pre-cracked specimens along the HAZ revealed that coarse grains promoted an increase in fatigue crack growth rate, hence causing a reduction in both fracture toughness and critical crack length, and a transgranular brittle final fracture with an area fraction of dimple zones connecting cleavage facets. A fractographic analysis proved that as the normalizing time increased the crack length decreased. The increase in the river patterns on the fatigue crack propagation in zone II was also evidenced and final brittle fracture because of transgranular quasicleavage was observed. Larger grains induced a deterioration of the fatigue resistance of the HAZ.

The corrosion behavior of gas metal arc welding (GMAW) regions has been studied using potentiodynamic polarization and polarization resistance (LPR) techniques. Experiments were conducted in hydrogen sulfide (H2S)-containing brine and in H2S-free brine. Welds were made on API 5L X52 steel. Due to differences in their microstructure, chemical composition and residual stress level, weld regions exhibited different responses under H2S corrosion. Base metal exhibited the highest corrosion rate (CR) and the most cathodic corrosion potential.

Se estudió el comportamiento ante la corrosión de las regiones de soldadura de un cordón realizado por arco metálico con gas (GMAW) sobre un acero grado API X52 mediante las técnicas de polarización potenciodinámica y resistencia a la polarización (LPR). Los experimentos se realizaron utilizando salmuera con 300 ppm de ácido sulfhídrico (H2S) y salmuera libre de H2S como electrolitos. Debido a las diferencias en su microestructura, composición química y el nivel de esfuerzos residuales, las regiones de soldadura mostraron diferentes respuestas a la corrosión por H2S. El metal base exhibió la velocidad de corrosión (CR) más alta y el potencial de corrosión más catódico.