Microstructure characterization of the weld cladding of clad steel plate A516 GR.70 - AISI 904L by electroslag strip cladding using Inconel 625 strip

This work investigates the effect of welding on microstructure and microhardness of the clad plate of ASTM A516 steel Grade 70 coated with AISI 904L steel, used in the manufacture of oil separator vessels. The plates were welded with a V-groove butt joint by gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), and submerged arc welding (SAW) employing mild steel filler wires. The joint back was then cladded with electroslag strip cladding using a single pass of Inconel 625 alloy. Microstructural characterization by optical microscopy reveals predominantly dendritic microstructures and hot cracks at the A516/904L and 904L/IN625 interfaces, with sensitization occurring at the A516/904L interface. Characterization by scanning electron microscopy and X-ray energy dispersive spectroscopy indicates a strong dispersion of deleterious phases identified as laves, sigma, and the NbC in the vicinity of the partially diluted zones, harmful to properties such as toughness and corrosion resistance. The A516/904L interface presented microhardness regions with values around 400 HV in partially diluted zones, equivalent to martensitic structures, usually associated with stress concentration and reduced fracture strength of the welded joint.