Materials Science and Engineering A239 – 240 (1997) 899 – 906 Abrasive wear of intermetallic-based alloys and composites J.A. Hawk *, D.E. Alman US Department of Energy, Albany Research Center, 1450 Queen Ae, SW, Albany OR 97321, USA Abstract In this study, the abrasive wear behavior of Fe 3 Al, TiAl, Ti 3 Al, Al 3 Ti, NiAl, Ni 3 Al and MoSi 2 , and composites based on these compounds, were assessed and compared to the behavior of selected metals, alloys and ceramics. Under the wear conditions used for these tests, the softer intermetallic compounds (e.g. TiAl and Fe 3 Al) behaved in a manner similar to the metals and alloys, whereas, the harder intermetallic compound (i.e. MoSi 2 ) behaved more like a ceramic. The influence of Al atomic fraction, superlattice structure and ternary alloying additions on the wear behavior of Fe 3 Al was investigated. Controlling the Al content and third element additions affected wear resistance more than superlattice structure. Composite strengthening was also explored as a method for improving wear resistance. The addition of hard second phase particles (i.e. TiB 2 to NiAl and SiC to MoSi 2 ) was also very effective improving wear resistance. Surprisingly, the addition of softer Nb particles did not significantly degrade the wear resistance of a MoSi 2 matrix, even at Nb additions of 40%. © 1997 Elsevier Science S.A. Keywords: Wear behavior; Abrasion; Intermetallic alloys; Intermetallic composites 1. Introduction Alloys, multiphase materials and composites are the key to technological advancement [1,2]. Modern materi- als are now being designed to provide the properties required for a particular application, either through microstructural control or by the use of composite concepts [3 – 6]. A particularly desirable class of ‘ad- vanced materials’ is the intermetallic compound [7]. The ordered structure inherent in many intermetallic alloys possesses several attractive properties, among them strength, stiffness and environmental resistance [8 – 10]. In addition, the long-range ordered superlattice reduces dislocation mobility, and at high temperatures, diffu- sional processes [11 – 13]. The inability of dislocations to easily move through the lattice results in low ambient temperature fracture-related properties, including ten- sile ductility and fracture toughness. These two at- tributes are critically important to engineers designing for structural applications, where ductility is needed for a material to function in the traditional sense. However, in wear related applications, loads are compressive in nature, therefore tensile ductility is not as critical a mechanical property parameter as hardness, strength, and work hardening ability. Consequently, intermetal- lics and intermetallic composites with hard particle reinforcements are also attractive for wear applications in severe, i.e. chemically aggressive, environments. Multiphase materials and composites are often used in situations where abrasive wear resistance is impor- tant. These materials typically consist of a matrix con- taining one to several reinforcing phases, usually in the form of particles, whiskers, fibers or fabric weaves. In the majority of cases, the reinforcing phase possesses a higher hardness, strength, or elastic modulus than the matrix, although it has been shown that the fracture toughness of brittle matrix composites with a ductile reinforcement can be increased, thereby improving the wear resistance of the composite [14,15]. Ideally, a composite combines the best of the individual compo- nent properties and suppresses the worst [16]. Thus, a material with relatively poor wear resistance can be improved with the addition of a suitable reinforcing phase. As previously mentioned, intermetallic compounds possess many attributes necessary for wear resistance – high strength, high elastic modulus, and good environ- mental stability. Because of their good environmental stability, these materials may find tribological uses in aggressive environments at elevated temperatures. Fur- thermore, the strength, hardness and fracture toughness of intermetallic compounds can be improved by * Corresponding author. 0921-5093/97/$17.00 © 1997 Elsevier Science S.A. All rights reserved. PII S09 21- 5093(97)0068 1- 3