Efeito da energia de soldagem na microestrutura e resistencia à corrosão do aço inoxidável superduplex UNS S32750 pelo processo TIG

Abstract

The superduplex stainless steel (SDSS) combine good mechanical properties and corrosion resistance, having a wide field of application in the petrochemical industry. Usually, the repairs of the equipment are made by welding, so the selection of parameters it is important. It is extremely important to obtain adequate ferrite content in the weld metal, and the variation of the welding energy can directly influence the microstructure and corrosion resistance. Therefore, this study aimed to evaluate the effects from the variation of welding parameters on the characteristics of SDSS UNS S32750. The rate phase was evaluated by relating this effect to the corrosion resistance. Welding in plates are made by GTAW autogenous process on 3 levels (5, 10, 18 kJ/cm), varying the current and welding speed so as to obtain 5 conditions and the possibility to analyze the response variables with this parameters alone. The microstructure analysis was carried out by optical microscopy and ferrite content was quantified by using two techniques: ferritoscope and imaging quantification. The test of critical temperature for pitting are made for analyses the corrosion resistance. It was concluded that the addition of energy by varying the welding speed resulted in an increase in ferrite content and a decrease of the critical pitting temperature, which are observed in the ferritic phase.