Analysis of the Creep Mechanism of Low-Alloy Steel in Terms of Plastic Deformation

As the proportion of renewable energy sources within the energy grid increases, boiler operations increasingly rely on managing disparities in energy supply. This condition substantially curtails their operational lifespan due to frequent switching cycles. Materials exposed to prolonged stress at high temperatures in harsh environments gradually degrade and eventually fail catastrophically. Thus, understanding processes like creep is essential for accurately evaluating the condition of operational components under new operational standards in power plants. In this regard, this paper introduces an innovative methodological framework for analyzing the creep mechanism, focusing on the plastic deformation of a crucial pipeline segment, specifically an elbow composed of 14MoV6-3 steel, both before and after extensive usage periods (164,000 and 302,000 h). The study explored the development of microstrain from the material's surface employing the electron backscattered diffraction method. This analysis assessed how operational durations influence dislocation structural changes, as examined by synchrotron radiation techniques, across a material depth from 0 to 1.5 mm. Based on these observations, the extent of deformation over time was demonstrated. Furthermore, the evolution of precipitation processes was investigated through transmission electron microscopy. These tests allowed to obtain and compare information on the dislocation structure of the tested steel after service in creep conditions, of small and large volumes of material.