Avaliação da resistência à corrosão de revestimento à base de inconel 625 utilizando os processos de soldagem MIG e plasma pó.

Abstract

The corrosion failures are the main cause of leakage in oil industry. Because of this new materials with higher corrosion resistance have been researched. One of the alternatives more used, for its low cost, is the application of coating by welding process. This work aimed first to find the better welding parameters to obtain the more adequate weld bead geometry, mainly the dilution, using a factorial statistical experimental design on two levels, and following to determinate its corrosion resistance using two welding process. Automatized Plasma Transferred Arc- Powder (PTA-P) and Metal Inert Gas (MIG) were used. The AWS ER NiCrMo-3Ni alloy, knowing as Inconel 625, in powder form with grain size 63 µm and in wire with 1,2 mm diameter were used as filler metals. API 5L X70 steel plate, used in pipeline for oil and gas transportation was used as base metal. The corrosion resistance was evaluated using linear potentiodynamic polarization and electrochemical impedance spectroscopy analysis. The Fe percents and microhardness test in weld bead surface were also done. The results showed that the weld bead hardness and its penetration and dilution obtained by PTA-P process were lower than those obtained by GMAW process. The coating obtained by PTA-P process also presented better corrosion resistance.