FRICTION AND WEAR BEHAVIOR OF C-4 AL2O3 AL COMPOSITES UNDER DRY SLIDING CONDITIONS/

The wear resistance of MMCs can be improved by increasing the volume f raction of the reinforcing ceramic phase (HRC) by as much as 70%. Amon g the various types of HRC composites, a new Al2O3-Al co-continuous ce ramic/metal composite (referred to as C-4 composite) has been recently produced at The Ohio State University. A new method of preparation, b ased on a displacement reaction between a silica precursor (whose fram e is faithfully reproduced in the composite product) and molten alumin um, allows the production of a MMC where both the Al2O3 and Al phases are continuous and interpenetrating. The aim of the present work was t o investigate the tribological behavior of C-4 Al2O3/Al composites und er dry sliding conditions using a computer-controlled slider-on-cylind er tribometer. The tests were carried out at applied loads in the rang e 5-30 N and sliding speeds in the range 0.3-1.8 m/s, for sliding dist ances up to 10 km. Wear scars and debris were characterized by means o f scanning electron microscopy (SEM), electron probe microanalysis (EP MA), with an EDS analyzer and Xray diffraction (XRD) analysis. Under t he adopted testing conditions, the C4 composites underwent only mild w ear, mainly as a consequence of the high load-bearing capacity of the ceramic phase which enhances wear resistance. The high wear resistance is also related to the nature of the third-body, mainly constituted b y Fe2O3, which is produced by the abrasive action carried out by the h ard ceramic phase on the counterfacing steel. Under the adopted testin g conditions, the transition from mild to severe wear, observed at a c ritical load in conventional MMCs, was never observed in the C4 materi als. Both the continuity between aluminum and alumina, and the increas e in interfacial bonding, played an important role in influencing the wear behavior of the C-4 composites. These aspects led to an improveme nt of wear resistance of the C-4 composites over conventional MMCs, un der the same experimental conditions, and probably shifted the transit ion from mild to severe wear regimes to higher critical loads. (C) 199 8 Elsevier Science S.A All rights reserved.