Research on the influence of self-healing, organicinorganic sol-gel layers on the corrosion resistance and fatigue of steel in the VHCF range

• Applicant: Dr.-Ing. Marek Smaga
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 465237729

The aim of the project is an analysis and explanation of protection and degradation mechanisms of steel substrates coated with self-healing organic-inorganic sol-gel coatings exposed to corrosive and fatigue load conditions.In the project, the sol–gel method is chosen for protective oxide coating preparation and modification. Synthesis routs will be optimized to obtain active, homogeneous and continuous coatings characterized by different hardness, on 904L and P265GH steel substrates. Proper protocols will be developed to obtain stable thin films doped by Ce(IV) nanoparticles or modified by ZrO2. Modification of the basic organic-inorganic matrix composition by introducing additional components (ZrO2, CeO2, and other Ce(IV) compounds) or by changing the catalyst (amount and/or type) of sol-gel reaction, will contribute to obtained protective, self-healing coatings with enhanced resistance to degradation under mechanical loads. The characterization of mechanical properties of coated samples under static and dynamic loads will be carried out with and without influence of a corrosive impact. FIB-SEM combined system will be used for characterization of initial state of SiO2+steel systems as well as the change of them due to fatigue. Cyclic loading of SiO2+steel systems with and without previously exposure in corrosive environment will performed for microstructural analyses at different observation. Modelling of damage process (initiation and crack propagation) in SiO2+steel system using fractal and movable cellular automata (MCA) methods will be developed. Data for modelling will be obtained from above mentioned investigations as well as from interfacial strength examination, for which own-elaborated measurement stand for thin layers will be prepared. The MCA simulations allow to reproduce heterogeneous microstructure of the proposed samples and model interactions of thin oxide layer with steel. The VHCF tests will be performed at specimens using an ultrasonic fatigue test system, working with a load frequency of 20 kHz in pulse/pause mode. The research should allow to receive information about enhancement of “true endurance limit” low carbon steel P256GH and austenitic stainless steel AISI 904L using thin coatings. Corrosion-fatigue VHCF tests will be performed. In presence of applied stresses, specific environmentally conditioned damage may thus take place in media that are inert when no mechanical stresses are present, due to corrosion-deformation interactions.The microscale and type of analysed compound material (substrate with coating) let us assume complex impact of differ factors. Standard approaches to material behavior description may not be enough in this case. The examples of interface research methods, which can be extended by standard tests, can be stated, that they will help in this project to understand the mechanisms and dependencies of the mechanical properties of the sol-gel oxide/metal interface. 

• DFG Programme: Research Grants
• International Connection: Poland
• Cooperation Partner: Dr.-Ing. Justyna Krzak