Agradecimentos: The authors are grateful to Conselho Nacional de Desenvolvimento Cientifico e Tecnológico (CNPq) - process number 142260/2016-9, FEM/UNICAMP for the facilities (SEM Zeiss EVO-MA15) and SULZER BRASIL SA for supplying the ASTM A890/A890M grade 6A steel. This research was supported by LNNano - Brazilian Nanotechnology National Laboratory, CNPEM/MCTIC, proposals: No. 18519 and No. 19209, for the use of DRX-P (X-ray diffractometer PANalytical X'Pert PRO MRD XL System), SEM and the durometer model Future-Tech FV 800 Ver menos

During welding of the superduplex stainless steels are exposed to thermal cycles, allowing precipitation of deleterious phases as well as unbalance as the ferrite and austenite phases. This work analyzed the microstructural changes taking place on a plate ASTM A890/A890M - grade 6A steel submitted to arc welding one welding of pass conducted on a flat surface using coated electrode Zeron®100, in the as welded and post-welded heat treatment conditions. Microstructural characterization in the regions base metal, heat affected zone, and fusion zone were conducted by optical microscopy, scanning electron microscopy and X-ray diffraction. The post-weld heat treatment in the fusion zone changed the ferrite/austenite volumetric fraction from 59/41 to 52/48. Cr, Mo and Ni distributions in the fusion zone were altered after the post-weld heat treatment, with the concentration ratio ferrite/ austenite being around 1.0; 1.1 and 0.9 to 1.1; 1.4 and 0.7, respectively. In addition, hardness reduced from 300 to 270 HV0.3 at the fusion zone Ver menos