P. Dodn IA. Hawk/ Wew 203-204(1997 )26y--177 ( cpay 136 54 by the respective manufacturers 100谥mA0 Ss am SiC AHO,+ Q7(09) (Table 2). For the monolithic aluminas, 99.8% AL-O, is asistant than is the 99.5% Al O, uter all study. In fact, with its high hardness and conditions tested. This large varia re toughness, al-o,+SiC is by far the m the two high purity 学 which, with its abrasive wearenvi- in alumina ceramics [25-291), although the difference in 3. 4. Microstrmcrurad response to the wear environment he wear surfaces immediately following ar rate for all SiC abrasive give hw址物邮9场AQ时的邮如可自的此址A again result of this study is the and examples of wear su dbmm减pire and dela of i hand, the addition of Sic whiskers leads to a dramane particles can penetrate more deeply into the surface of theC.P. Do&m. JA. Hawk/ Wear203-204 (1997) 267- 277 Young’s modulus (GPa)’ Hardners (GPa) Sifl.-A 310 15.6 5.4 SiIN.-A + SiC. 335 19.0 6.4 S&N,-B 303 15.0 5.5 Si,N,-B + SiC, 335 16.5 5.4 99.8% ~~0~ 400 19.3 3.4 99.5% Ai@> 386 15.2 3.9 AlzO, + SiC. 395 23.8 4.6 ’ Dntn provided by the rcspcaive manufactums. TPble 3 Abrasive war rawa for ceramics and ceramic composites (66.7 N nomnl load; 16.0 m sliding distance) 100 pm SIC 58 pm Sic 37pmsiC SisN.-A 0.9 (1.8) 9.1 (19.1) 6.6 (13.9) 2.5 (5.2) Si,N,-A + SiC, 1.0 (2.2) 9.9 (20.8) 6.8 (142) 1.8 (3.9) Z&N.-B 1.7 (3.7) 12.4 (26.1) 8.8 (18.6) 2.9 (6.2) Si3N.-B + SiC, 1.9 (4.0) 14.0 (Z9.4) 9.6 (20.2) 3.4 (7.1) 99.8% Al,o, 1.5 (3.2) 8.6 (18.0) 5.9 (i2.4) 2.1 (4.5) 99.5% Al,o, 6.4 (13.4) 23.6 (49.7) 22.1 (46.6) 5.3 (11.2) Al,O,+SiC_ 0.7 (0.9) 4.8(101) 3.3 (6.9) 0.9 (1.8) (Table 2). For the monolithic aluminas, 99.8% A&O, is much more V.VP -&ant than is the !XW& A!$, urder all conditions tested. This large variation in abrasive wearbehav￾ior between the two high purity ahuninas is most likely the result of the difference in grain size and grain s&distribution between the two materials (a smaller grain size and narrower grain sizedistribution is known to enhance wear performance in alumina ceramics [ 25-291). although the difference in grain boundary microstructure also plays a contributing role by influencing the residual stress state of Ihe ceramic [ 6,301. A comparison of the top performing silicon nitride (S&N.- A) with the top performing alumina (99.8% A&O,), shows that the alumina, with the higher ha&e88 but lower fracture tOughIh?SS, possesses a lower wear rate for all SIC abrasive environments. Against the softer aluminabrasive, however, Si,N4-A has a 75% lower wear rate than the 99.8% A1203. thanks to its higher fracture toughness. Perhaps the most interesting result of this study is the observation that tbe addition of 15 vol.% SE whiskers to a silicon nitride matrix either does not affect the abrasive wear behavior of the bulk material, or degrades it slightly in some instances (Figs. 2 and 3). This cccur8 in spite of the fact that the addition of SiC whiskers increases the hardness of both Si,N,materials and increases the fracture toughness of S&N,- A. The only exception to this rule is in the SisN,-A ceramics tested against 400-grit Sic, where the composite outperforms the monolith In the alumina-based ceramics, on the other hand, the addition of Sic whiskers leads to a dramatic improvement io the abrasive wear resistance under all test conditions of this study. III fact, with it8 high ha&e88 and respectable fracture toughness, A&O, + Sii is by far the most wear resistant material examined in thii study. This is in stark contrast to the 99.5% A1203 which, with it8 low hardness and propensity for fracture in all abrasive wearenvi￾ronments. is clearly the worst performer. 3.4. Microstructural response to the wear environment In addition to the measured response to various abrasive wear environmenta listed in Tablea 3 and 4. examination of the wear sorf8ces immediately following the wear tests can give clues to the influence of micro8hucture and whisker reinforcement on the wear behavior of a ceramic material. A8 an example, micrograph of the wear surface8 following abra￾sion against tbe h8rder U&grit SE are provided in Pig. 4, and examples of wear surfaces produced by tests against tbe softer HO-grit Al,Os arc given in Fig. 5. Comparison of tbe micrograpbs in Figs. 4 and 5 clearly indicate varhtions in the microstructural response ofthedifferentccram&totheabra￾sive wear environments. For the A-silicon nitride materials, the principal re8ponse to the Sic wear en vironment [Fig. 4(a) and (b)] is plastic deformation, although fmcture at wear groove peripheries and delamination within the grooves is also rexlily rppraent Because of its relatively lower hardness. tbe Sii abrasive particles can penetrate more deeply into the surfa~x of the