ures, hardness, fracture toughness and wear behavior of both ies and ceramic composites of this study were identically the reinforced and unreinforced materials. 2 Experimental particle sizes of 37, 58 an Three commercially available, SiC-whisker reinforced tests the The htst pair of sitcom nitnoe-base matrix. Because no similarly processed monolithic alumina 99.5% Al,on of constant was calculated according to the equation [221 In these equations, Am was the mass loss of the test specimen secondary clectron imaging mode. Sample preparation for normal load(N)on the specimen; and e pre by coating with a Au-Pd alloy to prevent charging in the wear rate or the wear constar st results of greater than +5.5% attributed to real differences in the wear behavior of the materials. easurements were taken for each material, with the results rements were made for each 99.8% A1-O, can be found in simulate abrasion bonded by a continuous crystalline ver, it is important to recognize that during this test the boundary phase. The composition sample was contimuallyexposed to fresh abrasive. Tbecetam- boundary phas end upon the additives and impurities268 C.P. Do&m. J.A. Hawk/ Wear 203-204 (1997) 267-277 mres, hardness, fracture toughness and wear behavior of both the reinforced and unreinforced materials. 2. Experimental Three commercially available, Sic-whisker reinforced composite materials were selected for this study, along with several chemically similar but unreinforced matix materials for comparison. The first pair of silicon nitride-based mate￾rials, S&N,-A and S&N,-A + SIC,, were processed in an identical manner, except for the addition of 15 vol.% SIC whiskers to the composite material. The second series of silimn _..L...C nrAA^-5ised Y ceramics, S&N.-B and S&N.,-B +SiC,, were processed somewhat differently than the hrst, in order to produce a different matrix microstructure; the composite material also contained i5 vol.% SE whiskers. For the alu￾mina-based materials, the composite, A120~+SiC,,., con￾sisted of 34 vol.% SE whiskers in a high-purity alumina matrix. Because no similarly processed monolithic alumina was available, two high purity ahuninas-a 99.8% AlzO, of relatively high hardness, and a 99.5% A1203 of intermediate hardness-were selected for comparison with tbe composite. Microstructural characterization of these materials was accomplished primarily by transmission electron microscopy (TEM), in combination with chemical analysis by X-ray energy dispersive spectroscopy (XBDS). Analysis of the materials’ microstructural response to the various abrasive wear tests was by scanning electron microscopy (SBM) in secondary electron imaging mode. Sample preparation for TBM analysis followed traditional ceramographic tech￾niques, including ion milling to electron transparency. Sam￾ple preparation for SEM analysis was limited to ultrasonic removal of the wear debris from the wear surfaces, followed by coating with u Au-Pd alloy to prevent charging in the microscope Hardness and fracture toughness were measured for each material on surfaces mechanically polished to a 1 km dia￾mond 8nish. Vickers hardness was determined under a load of 1 kg, with a dwell time of 15 s. Ten separate hardness measurements were taken for each material, with the results averaged. Fracture toughness was measured utilizing the indentation technique described by Anstis et al. [ 191 with the indenting load varied between 10 and 20 kg. depending on what was required to develop a well-defined crack pattern with a measured crack length that was at least three times the diagonal diameter. A minimum of five fracture toughness me‘asurements were made for each material and the results averaged. Material response to two-body abrasive wear was meas￾ured utilizing a pin abrasion test designed at me Albany Research Center to simulate abrasion mat occurs during crushing and grinding operations. This test is described in detail elsewhere [ 201, and will not be discussed here-; how￾ever, it is important to recognize that during this test the sample was continually exposed to fresh abrasive. Theceram- 3. Results 3.1. Microstructure Micrographs illustrating the general microstructural fea￾tures of the three composite materials, and &he monolithic 99.8% A&O,, can be found in Fig. 1, and an outline of the microstructural characteristics of all of the ceramics exam￾ined in this study can be. found in Table I. With the exception of the 99.8% Al,O,, all ceramics and ceramic composites are liquid-phase sintered materials in which the matrix grams are bonded by a continuous crystalline and/or amorphous grain boundary phase. The composition and nature of these gram boundary phases depend upon the additives and impurities