Modeling solid-particle erosion of ductile alloys
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I. INTRODUCTION
SOLID-particle erosion is a loss of material during repetitive impacts of solid particles and is one of the primary reasons for fly ash–borne damage of power generation components. A description of the erosion mechanism in terms of the mechanical properties was presented by Bitter.[1] During impact, when the yield strength of the material is locally exceeded, plastic deformation takes place in the vicinity of the impact. After multiple impacts, a plastically deformed surface layer may form near the eroded surface, and, therefore, the yield strength of the material increases due to strain hardening. Upon further deformation, the yield strength at the surface of the material will eventually become equal to its fracture strength, and no further plastic deformation will occur. At this point, the material surface becomes brittle and its fragments may be removed by the subsequent impacts. Some researchers have suggested that, during erosion, material loss from a metal surface occurs when a critical fracture strain is achieved at the surface.[2] A critical fracture strain may be achieved locally after single or multiple impacts by the erodent particles. As material is lost at the attainment of the critical strain, the material below the surface is still plastically yielding. Ball[3] proposed that, in order to design a material to resist erosion, attention must be given to providing a microstructure that, ideally, never accumulates the critical fracture strain under the stress that the impacting particles impose. Therefore, the ability of a material to accommodate impact energy may contribute to its erosion resistance. Many studies have been conducted to determine the effect of mechanical properties, chemical composition, and the microstructure of various materials on their erosion resistance. However, good correlations between these parameters have been obtained only within narrow classes of materials. By determining the effects of mechanical properties on erosion resistance, the microstructure of a given alloy could be B.F. LEVIN is Staff Engineer with A.T. Kearney, Inc., Chicago, IL 60609. K.S. VECCHIO, Associate Professor of Materials Science, is with the Mechanical and Aerospace Engineering Department, University of California, San Diego, La Jolla, CA 92093-0411. J.N. DuPONT, Research Scientist, Energy Research Center, and A.R. MARDER, Professor, Materials Science and Engineering Department, Whitaker Lab, are with Lehigh University, Bethlehem, PA 18015. Manuscript submitted May 14, 1998. METALLURGICAL AND MATERIALS TRANSACTIONS A
optimized to provide the best combination of mechanical properties for erosion protection. Hardness is the most widely used property to correlate with the erosion rates of materials. For pure metals, some correlation between erosion rate and hardness has been shown.[4] However, several other observations have shown that the erosion rate is not dependent on material hardness.[5,6] Hutchings[7] proposed that the effect of hardness on erosion resistance is strongly dependent on t
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