Avaliação do envelhecimento a 475ºC em soldas de tubo aço inoxidável superduplex UNS S32750 por ensaio de dureza

Abstract

The present work has the objective of analyzing the hardness changes in a Weld in the Stainless Steel Super Duplex UNS S32750 welded by the process of tubular wire when subjected to a thermal treatment at 475oC. A study was carried out on samples submitted to welding with energies of 0,5 kJ/mm and 1,0 kJ/mm, later evaluating changes in physical properties in the material, with the main focus on variations in the hardness of materials and phase balance. The samples were divided into four groups, according to the different thermal aging treatments to which they were submitted, in duplicate form: as welded and aged at 475oC for periods of 10, 50 and 100 hours. The results to be presented were obtained from the relationship between Vickers microhardness tests and phase balance, indicating microstructural variations after the welding process. The obtained results showed clearly that the materials exposed to the different times of heat treatment had significant changes in their values of microhardness. Beyond that the different welding energies were shown as a determinant factor for a difference in phase balance, according to measurements by image analysis. It was also observed the difference in the precipitation kinetics between the base and molten zone regions, which presented a higher hardening effect after the treatment.