Modelling of Short Corrosion Crack Growth of Low-Alloy Steel in a Chemical environment

Abstract

This study aims to develop a theoretical model for short corrosion crack growth rate happen in some of pre-cracked specimens made of three types of low-alloy steel. The selected material is widely used in boiler pipes of electrical power plants. An experimental system was established to simulate the real work conditions, so the specimens subjected to dynamical loading procedure under different chemical environment conditions at different testing temperatures. The results described the behavior of the material under the testing conditions, and showed that the crack growth rate was accelerated due to corrosion contribution, especially at high temperatures, so the classic mechanical crack growth rate under air at room temperature may be neglected as compared with that resulted due to corrosion and temperature interaction. A mathematical model was developed beginning from the superposition model to describe the total crack growth rate of the pre-cracked specimens, depending on many of introduced parameters, such as corrosion density, water chemistry, time of test, crack geometry, loading frequency, stress intensity, velocity of environment liquid motion through the crack walls, and thermal activation energy due to difference in test temperatures. Furthermore, some of important conclusions were outlined.

Keywords: corrosion fatigue crack, crack growth, mathematical model