Erosion of alumina and silicon carbide at low-impact velocities J.G. Chacon-Nava a, * , F.H. Stott b , S.D. de la Torre a , A. Martı ´nez-Villafan ˜e a a Centro de Investigacio ´n en Materiales Avanzados, S.C., Divisio ´n de Deterioro de Materiales, Ave. Miguel de Cervantes 120, Complejo Industrial Chihuahua, 31109 Chihuahua, Chihuahua, Mexico b Corrosion and Protection Centre, University of Manchester Institute of Science and Technology, Sackville Street, M60 IQD, Manchester, UK Received 6 June 2001; accepted 19 October 2001 Abstract The erosion performance of two commercial ceramics, alumina (Al 2 O 3 ) and silicon carbide (SiC), has been studied in a laboratory fluidized-bed (FB) facility in the temperature range from 250 to 560 jC. Tests were carried out in air using angular alumina particles with an average size of 100 Am as erodent material at an impact velocity of 5 m/s. The SiC ceramic revealed a better erosion resistance than Al 2 O 3 , irrespective of temperature. It is assumed that, at testing temperatures, oxidation plays no transcendental role in the extent of damage. Instead, under present conditions, the high hardness value conferred into the ceramics through higher densifications might lead to a better erosion resistance. At temperatures above 250 jC, SEM analysis on the surface of both ceramics disclosed ripple formation, i.e. a plastic deformation process occurring under particle impaction. This was less evident at the lowest testing temperature. Reasons to explain the behavior found are discussed. D 2002 Elsevier Science B.V. All rights reserved. Keywords: Ceramic materials; Erosion behavior; Low-impact velocity; Plastic deformation; Ripples; Fluidized-bed combustors 1. Introduction Ceramic materials have been widely used for a number of industrial processes. Advantages of ceramics, as compared with metals, include good chemical and temperature stability, medium density and high hardness [1]. In general, these properties encourage potential applications such as wear-resistant materials for several engineering designs and situa- tions. For instance, Al 2 O 3 and SiC ceramics have been used for gas turbine parts, sealing bearings, sinter plants, burner barrier dampers, burner scrolls and pulverized coal lines [1–4], just to mention a few. Such applications demand a high erosion resistance from the material being tested. The erosion of materi- als by impact of solid particles is a form of wear process in which the material is removed from a surface by the impingement of hard particles, usually accelerated by a gas flow. Depending upon the process involved, impact velocities are in the range from 20 to 300 m/s. In spite of this, specific working conditions involve impact velocities below 20 m/s. As an exam- ple, components, such as in-bed heat exchangers in fluidized-bed combustors, can suffer particle impact velocities in the range of 1 – 6 m/s [5]. At these velocity conditions, only a few studies involving ceramic ma- terials have been reported [6–9]. Thus, the aim of the present work has been to investigate the performance of the two ceramics described above, exposed in a simulated fluidized-bed environment at low-impact velocity conditions. 0167-577X/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. PII:S0167-577X(01)00659-0 * Corresponding author. www.elsevier.com/locate/matlet August 2002 Materials Letters 55 (2002) 269 – 273