Assessment of resistance to hydrogen embrittlement of cryorolled AISI 317L austenitic stainless steel and after austenite reversion: microstructure and mechanical properties

• Grant number: 24/20140-6
• Support Opportunities: Regular Research Grants
• Start date: July 01, 2025
• End date: June 30, 2028
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Physical Metallurgy
• Principal Investigator: Hugo Ricardo Zschommler Sandim
• Grantee: Hugo Ricardo Zschommler Sandim
• Host Institution: Escola de Engenharia de Lorena (EEL). Universidade de São Paulo (USP). Lorena , SP, Brazil

Abstract

This project aims to study the behavior of 317L steel rolled at 77 K and after austenite reversion against hydrogen. The ongoing energy transition and the development of an economy based on hydrogen require a reassessment of the mechanical behavior of traditional materials, but with optimized microstructures, tolerant to this gas. The deformation microstructure is quite complex, consisting of alpha-prime-martensite as the main constituent (volume fraction of 0.70), stacking faults, nanotwins and untransformed austenite. This huge range of microstructural defects offers different types of trapping sites for hydrogen atoms and promotes a reduction in the diffusion coefficient down to values on the order of 10-16 m2/s at room temperature. During heating to 700oC, the reversion of alpha-prime-martensite into austenite is almost completed, as well as the reduction in the dislocation density and other planar defects. Microstructural characterization will be complemented with Transmission Kikuchi Diffraction (TKD) mappings coupled to spherical indexing to characterize the cryorolled steel and samples annealed in the range of 600-700oC to evaluate microstructural refinement after reversion. Tensile tests in miniaturized specimens will be carried out on deformed samples and under various hydrogen charging conditions. Thermal desorption spectroscopy (TDS) will be carried out on samples saturated with hydrogen to determine the activation energies associated with different hydrogen trapping sites. Hydrogen permeation measurements up to 700oC will be carried out to determine the diffusion coefficient in representative samples. (AU)