Ravish/hā-yi ̒adadī dar Muhandisī (Sep 2021)
Numerical and Experimental Evaluation of Pitting Corrosion of CUSTOM 450 Stainless Steel Alloy in Chloride Environment
Abstract
Corrosive factors along with mechanical loads on the gas turbine compressor blades, cause phenomena such as pitting corrosion, stress corrosion cracking and corrosion fatigue. Due to erosion of particles in the presence of a corrosive environment, pitting happens on the blade surfaces, which is a source of subsequent cracks. Therefore, it is necessary to get knowledge of its mechanism in order to prevent the phenomena as much as possible. The main purpose of this paper is to investigate the growth of pitting corrosion in CUSTOM 450 stainless steel and to obtain strain values in the growing pits at the maximum bending region. In this regard, a two-point bending specimen was made and subjected to a potentio-static test under the potential of 350 mVSCE in the 3.5 wt% sodium chloride solution. Then the propagated pits were numerically examined. By the digital image correlation method, the local strain was calculated in the pits and a relation was presented to obtain the maximum strain time. Therefore, growth direction of pitting corrosion could be estimated by having maximum strain region. Finally, by simulating the pitting corrosion process of a stress-free sample under the potential of 350 mVSCE in 3.5 wt% sodium chloride solution in COMSOL Multiphysics software, variations in the concentration of ions, electric potential, and corrosion current density were shown in the existing pit. The potential was decreased by moving in-depth and the maximum current density was found at the depth of 18 μm. Thus, without the need of advanced laboratory facilities for surface scanning and analysis, useful information from surface corrosion conditions could be obtained
