A CFD model was developed to predict with accuracy the local electrochemical performance in an operating solid oxide fuel cell. A particular focus was given on the study of performance limitations and degradation sources caused by the design of the fuel cell, by the choice of materials and components, or by improper operating points. The model is used to understand typical degradation effects observed on stacks tested in collaboration with HTCeramix - SOFCpower. The model is able to predict several degradation effects caused by the use of compressive seal materials with remaining open porosity. Diffusion across seals is modeled, as well as the resulting parasitic combustion of air and fuel. The risk of local redox-cycling for the anode supported cell is evaluated locally, as well as an eventual local reduction of the cathode layers. The cracking of electrolyte caused by redox cycles is modeled locally, with increasing gas leakage at each cycle, allowing to model the cumulative effect of successive critical operating points. The results are compared with experiments, showing an overall good agreement.