Mechanisms of Erosion/Corrosion of Metals and Their Oxide Scales

摘要

The presence of small particles of coal and char in moving reactive gases at elevated temperatures in coal gasifiers creates a hostile environment that has caused surface degradation of metallic components in pilot plant operations. The objective of the work reported herein is to provide some insight into the basic mechanisms of degradation that occur when a small particle impacts on a bare metal surface or on one that contains a thin oxide scale. It is hoped that understanding how material is removed from the surface will provide the basis for selecting operating conditions and developing more resistant materials that will result in less materials degradation. The work to date indicates that significant differences in erosion behavior do occur as the result of different elevated temperature corrosion conditions forming different scale and interface compositions and morphologies. Generally the differences were relatively minor. However, under conditions of combined erosion-corrosion, these differences could become important. Even though the scales were thin and on ductile matrices, their erosion behavior variation with impingment angle was that of a brittle rather than a ductile material. The use of erosion tests to study the adherence of various scales has some merit. However interpretation of some of the smaller differences could be difficult. (ERA citation 06:015206)