Austenitic stainless steels affected by sulfides and carbides: surface recovery by LASER remelting

• Grant number: 23/07379-7
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree
• Start date: September 01, 2023
• End date: February 29, 2024
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Physical Metallurgy
• Principal Investigator: Guilherme Yuuki Koga
• Grantee: Ana Larissa Soares Cruz
• Supervisor: Roche Virginie
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Institution abroad: Université Grenoble Alpes (UGA), France
• Associated to the scholarship: 22/08457-9 - Austenitic stainless steels imparied by sulfides and carbides: Surface recovery by LASER remelting, BP.MS

Abstract

Austenitic stainless steels, especially AISI 304 and 316L, are recognized for their high mechanical strength, toughness, and corrosion resistance in various applications. Sensitization in AISI 304 and the presence of manganese sulfide (MnS) in AISI 316L are the main causes of susceptibility to intergranular and pitting corrosion, respectively. Sensitized steels and steels with high concentration of MnS require costly treatment processes to recover corrosion resistance. Since electrochemical corrosion is a process initiated on the surface, laser surface remelting (LSR) can be a fast and effective method for carbide dissolution and MnS evaporation, given the process characteristics: high energy density, and high heating and cooling rates. This work has as objective the recovery by LSR of sensitized steels and steels compromised by MnS. Heat treatments will be applied with the aid of thermodynamic calculations, inducing sensitization in AISI 304. A 316L with appreciable MnS will be considered as starting material for MnS surface removal. The steels as received, after heat treatment (for AISI 304) and remelted with LASER with different energy densities, will be chemically and microstructurally characterized by scanning electron microscopy. In addition, their susceptibility to intergranular corrosion (ASTM A262, Practice A), degree of sensitization (ISO 12732) and resistance to pitting corrosion will be evaluated, the latter investigated by cyclic potentiodynamic polarization (ASTM G61) in 0.6 M NaCl solution. The passive films developed in 0.6M NaCl for the different processing conditions will be evaluated by electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy (XPS). The aim is to correlate the thermal cycle induced by LSR with: dissolution and prevention of chromium carbide reprecipitation and MnS vaporization. By the end, we expect to verify the effectiveness of LSR as a surface engineering technology for the recovery of austenitic stainless steels compromised by sulfides and carbides. (AU)