Structural characterization and electrochemical Corrosion of Spray-Formed boron modified superduplex stainless steel

• Grant number: 18/19968-9
• Support type: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): November 01, 2018
• Effective date (End): October 31, 2019
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Physical Metallurgy
• Principal researcher: Guilherme Zepon
• Grantee: Ricardo Mimo Halak
• Home Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated research grant: 13/05987-8 - Processing and characterization of amorphous, metastable and nano-structured metallic alloys, AP.TEM

Abstract

High wear and corrosion resistance are basic requirements for materials used in severe conditions such as those encountered in the petrochemical industry. Super duplex stainless steels are possible candidates to be considered in such applications because of their interesting combination of mechanical properties and excellent corrosion resistance. Super duplex stainless steels, when modified with additions of boron, may exhibit a corrosion-resistant matrix reinforced with wear-resistant borides. The spray forming process is an interesting route to produce stainless steels containing boron, favoring the formation of a dense, refined and homogeneous microstructure. Recently, it has been shown that that spray-formed boron-modified super duplex stainless steels modified have excellent wear resistance. However, the corrosion resistance of these steels has not yet been evaluated. The purpose of this research project is to characterize the microstructure and evaluate the corrosion resistance by electrochemical methods of a boron-modified super duplex stainless steel produced by spray forming. An alloy with composition in which the borides are formed at the end of the solidification in a eutectic-type reaction, and that forms a matrix with balanced fractions of ferrite and austenite, will be evaluated. The microstructure will be characterized by optical microscopy, X-ray diffraction and scanning electron microscopy. Potentiodynamic polarization tests followed by inspection of the attacked surface will be used to evaluate the corrosion resistance of the alloys to pitting. At the end of the work, it is expected to confirm that (I) the addition of boron induced the formation of dispersed hard borides in a duplex stainless matrix, and (II) whether the resulting microstructure has high corrosion resistance in environments rich in chloride ions.