Stress Assisted Corrosion of Water-wall Tubes in Waste Heat Boiler- Failure Analysis

摘要

Stress-Assisted Corrosion (SAC) can cause failures in the waterside tubes of carbon steel boilers. SAC is defined as the attack at locations where applied and/or residual stresses are imparted to the metal. This paper presents a failure investigation of waste heat boiler carbon steel tubes at one of the Saudi Basic Industries Corporation (SABIC) affiliates. The tubes were obtained from an evaporator section in the waste heat boiler for investigation. Metallographic examinations were performed on the removed tube to evaluate the microstructure of the tube material. Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) was used to study the cracks morphology and the chemical compositions along the cracks. Finite element was used to evaluate the stresses on the tubes. Mechanical properties of the tube materials were evaluated as well. The results of the conducted analyses confirmed the failure of waste-heat boiler tubes was related to SAC.