WEAR Influence of whisker reinforcement on the abrasive wear behavior of silicon nitride- and alumina-based composites CP.Do总an,JA.Hawk Albany Research Ceater Deparment d Energy Ahu. OR 97521054 behavior is atunbuted to the r Keyword: Composites: Abrasve wear Amund, MIcowucTure nction of the ha ecton [9- ng crack. Thus, while the long- crack toughness of the bul whisker t en noted that ine have addressed the relative perfo forced behavior of several silicon nitride. and al mina-based ceramic materials by companing ue microst c043-1648/97/SI7 00c 1997 Elsevier SclenceS A. All righes resendELSEVIER WEAR Wear 203-204 ( 1997) 267-277 Influence of whisker reinforcement on the abrasive wear behavior of silicon nitride- and alumina-based composites C.P. Dogan, J.A. Hawk Albany Research Cenrrr. Deportmmr of Energy Albany. OR 97321. USA The abrasive wear of brittle materials, while not a tme property of materials, is generally modeled as an inverse limction of both the bulk hardness and frashue toughness. According to these models. an increase in the hardness and/or fmcture tott@ of a material will thereforr enhance its wear resistance. In ceramic mat&Is, the addition of whisker reinforcement is a pmven method ofe&ancing long-crack fmcmm toughness via such mechanisms as crack bridging attd wbiskerdcbondittg. However, less is known about bow wbiskerreinforcementingtzmes the properties that arc dependent upon the shott-ctack oughttess. such as abrasive wear. The results of this study indicate th8t while the addition of randomly oriented SE whiskers can dramatically improve the abrasive wear resistance of an abmdna-based ceramic. the arkiition of Sic reinforcement to silicon nitride ceramics does not always result in improved wear resistance. This wtriation in the intluence of whisker ninforcetnent on wear behavior is attributed to the residual stress state created in the composites as a result of the addition of the second phase whiskers. Keywordc Composites; Abrasive wear. Silicon nitride; Alumina; Micmsmxture 1. lntroductioa Because of the complexity of wear processes, a detailed understanding of how ceramic materials react in trihological environments continues to elude both materials and design engineers. For the abrasive wear of brittle materials. mathe￾matical models generally express volume wear as an inverse function of the hardness and the fracture toughness of the material [ 1,2]. However, these. models fail to adequately describe the abrasive wear behavior of most advanced ceramic materials in at least one important way: they assume that bulk hardness and fracture toughness measurements are sufficient to describe the deformation and fracturecharacter￾istics of the test material in an abrasive wear environment. A number of studies on a wide variety of ceramic materials have indicated that this is not the case [3-S]. In particular, it has been noted that in ceramic materials which exhibit increasing fracture toughness with increasing crack length (called R￾curve or T-curve behavior), such as alumina and zirconia ceramics and many ceramic-based composites, the measured bulk fracture toughness may not describe the fracture tougb￾ness of the ceramic at the micmstructural scale where abrasive wearmechanismsareactive [6-g]. Ceramic-reinforced ceramic composites represent one of the best developments so far in the race to produce tough, yet 0043.1648/97/$17.OO Q1997 Elsevier Science .%A AU tights reserved PllSOO43.1648(96)07348-6 mechanically reliable, ceramic materials for advanced sttttc￾turalapplications,andp~cular)yforapplicationsatelevated temperatures. Over the course of the last decade, much research has gone into the tmderstandhtg of precisely how the addition of reinforcement phases can intloence the strength and toughness of the bulk ceramic material. For whisker-reinforced ceramic materials, enhanced toughness can occur through any one. or several, of the followhtgmech￾anisms: whisker &bonding, whii pullout, crack bridging. and/or crack deflection [S-14]. However, in almost eveq case, :arge-scaie toughening requires that these mechanisms be activated over some distance behind the tip of a propagat￾ing crack. Thus, while the long-crack toughness of the bulk material may be enhanced by the pmsence of the whisker reinforcement, the short-crack toughness of the bulk material may remain ttnchanged, or even ba degraded, by the preaenca of these whiskers. Studies of how the preseneo of whisker reinforcement influences the ttibological pmpetties of ceramic materials are largely absent, although sevaral studies have addressed the nlative performance of whiia-rein￾forced ceramic matrix composites in sling and abrasive wear environments [45.15-111. In thii study. we begin to examine how randomly oriented SE whiskers ittflucnce the abrasive wear behavior of several silicon nitride- and aht￾mina-based ceramic materials by comparing the micmsbuc-