Effects of Hydrogen Embrittlement on the Mechanical Behavior of Additively Manufactured High-Entropy Alloy Cr45Co27,5Ni27,5

• Grant number: 25/04644-7
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: August 01, 2025
• End date: July 31, 2027
• Field of knowledge: Engineering - Materials and Metallurgical Engineering
• Principal Investigator: Claudemiro Bolfarini
• Grantee: Thiago Roberto Felisardo Cavalcante
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated research grant: 22/02770-7 - Integrated Computational Materials Engineering ICME: applied to modeling, production, characterization and testing high entropy alloys, AP.PNGP.PI

Abstract

Hydrogen embrittlement (HE) represents a significant challenge regarding the structural integrity of metallic alloys used in engineering applications, such as aeronautical and automotive industries, especially when processed through additive manufacturing (AM). Due to its versatility and considerable potential, AM has attracted remarkable interest from the international scientific community, particularly in processing high-entropy alloys (HEAs), owing to its unique capability to produce near-net-shape geometrically complex parts, characterized by highly localized melting and solidification conditions that result in non-equilibrium microstructures with mechanical properties potentially superior to those obtained through conventional routes. Various HEA systems have been successfully processed via AM, including CrMnFeCoNi, CrFeCoNi, AlCoCrFeNi, and AlCoCrFeNiTi0.5, as well as variants with compositional gradients and laminated structures. This research aims to evaluate the HE susceptibility of high-entropy alloy Cr45Co27,5Ni27,5 when fabricated by powder bed fusion with laser beam (PBF-LB), examining how AM-specific microstructural characteristics such as residual stresses, porosity, segregation and anisotropy influence hydrogen absorption and diffusion. The project will involve electrochemical hydrogen charging, mechanical testing (tensile, slow strain rate test and fracture toughness) and microstructural analysis through scanning electron microscopy, electron backscatter diffraction and transmission electron microscopy and X-ray diffraction, as well as atom probe tomography and thermal desorption spectroscopy techniques, evaluating the effects of PBF-LB processing parameters, hydrogenation and heat treatments on HE mitigation. The results are expected to contribute significantly to the selection and processing of high-entropy metallic alloys through AM, ensuring their structural integrity in hydrogen-rich environments. From a scientific point of view, it should be emphasized that the intrinsic structure of high entropy alloys represents a unique environment for the study of hydrogen embrittlement of metallic alloys because the mechanisms of hydrogen diffusion and effect must be totally unique in these alloys, which can reveal or add a lot of knowledge to this phenomenon, which is still poorly understood for steels and titanium alloys. This knowledge might, eventually, be transferred to other metallic systems. (AU)