Microstructure and wear properties of AlSi-Al<SUB align=right>2O<SUB align=right>3 and AlSi-SiC-Al<SUB align=right>2O<SUB align=right>3 interpenetrating composites produce

Abstract

Reactive metal penetration (RMP) has been used to produce interpenetrating phase composite (IPC) materiaReactive metal penetration (RMP) has been used to produce interpenetrating phase composite (IPC) materials. These materials differ from classical metal matrix composite (MMC) structures (i.e. a discrete reinforcement within a continuous matrix) in that their microstructure consists of co–continuous or interpenetrated metal and ceramic phases. Two types of IPC materials were produced the first was an Al2O3 (70 vol.%)–AlSi20 (30 vol.%) composite; the second was constituted by SiC particles (~50 vol.%) dispersed in an interpenetrating Al2O3 (32 vol.%)–AlSi20 (18 vol.%) matrix. These composites have been targeted to wear applications and for this reason their tribological behaviour has been studied. The friction and wear tests were carried out under dry sliding conditions against steel (a surface ardened AISI 1040) and ceramic (an Al2O3–TiO2 coating plasma–sprayed onto an AISI 9840 steel) countermaterials, at various applied loads and sliding speeds. The wear resistance of these new composites has been also compared with that of conventional particulate reinforced aluminium metal matrix composites. In the case of dry sliding against steel, both IPC materials showed a mild wear regime, with also negligible wear of the counterface; the coefficients of friction ranged from 0.6 to 0.8 (the lower values being measured at the highest sliding speed). The worn surfaces were always covered by an iron–oxide transfer layer, which formation was clearly due to the abrasive action of the ceramic phases against the steel countermaterial. The presence of this layer reduced the wear damage of both counterfacing surfaces. The IPC materials, moreover, exhibited a greater wear resistance respect to the conventional aluminium MMCs, due to both the high volume fraction of the ceramic phases and to the good interfacial bonding between the interpenetrating phases. Substantially different was, instead, the tribological behaviour of the studied composites against the ceramic coated countermaterial. Severe wear both of the IPC materials and of the countermaterial was observed, in almost all the investigated testing conditions, with coefficients of friction around 0.45. Wear mainly occurred by brittle fracture of the ceramic phases and, once the ceramic phases were fractured, the relatively low fracture toughness of the composite negatively affects their wear resistance.ls. These materials differ from classical metal matrix composite (MMC) structures (i.e. a discrete reinforce– ment within a continuous matrix) in that their microstructure consists of co– continuous or interpenetrated metal and ceramic phases. Two types of IPC materials were produced the first was an Al2O3 (70 vol.%)–AlSi20 (30 vol.%) composite; the second was constituted by SiC particles (50 vol.%) dispersed in an interpenetrating Al2O3 (32 vol.%)–AlSi20 (18 vol.%) matrix. These composites have been targeted to wear applications and for this reason their tribological behaviour has been studied. The friction and wear tests were carried out under dry sliding conditions against steel (a surface ardened AISI 1040) and ceramic (an Al2O3–TiO2 coating plasma–sprayed onto an AISI 9840 steel) countermaterials, at various applied loads and sliding speeds. The wear resistance of these new composites has been also compared with that of conventional particulate reinforced aluminium metal matrix composites. In the case of dry sliding against steel, both IPC materials showed a mild wear regime, with also negligible wear of the counterface; the coefficients of friction ranged from 0.6 to 0.8 (the lower values being measured at the highest sliding speed). The worn surfaces were always covered by an iron–oxide transfer layer, which formation was clearly due to the abrasive action of the ceramic phases against the steel countermaterial. The presence of this layer reduced the wear damage of both counterfacing surfaces. The IPC materials, moreover, exhibited a greater wear resistance respect to the conventional aluminium MMCs, due to both the high volume fraction of the ceramic phases and to the good interfacial bonding between the interpene– trating phases. Substantially different was, instead, the tribological behaviour of the studied composites against the ceramic coated countermaterial. Severe wear both of the IPC materials and of the countermaterial was observed, in almost all the investigated testing conditions, with coefficients of friction around 0.45. Wear mainly occurred by brittle fracture of the ceramic phases and, once the ceramic phases were fractured, the relatively low fracture toughness of the composite negatively affects their wear resistance.