Preparation and Properties of Sintered Copper-Tin Composites Containing Copper Coated or Uncoated Fly Ash

Copper-5%tin-fly ash mixtures containing 0-16 wt% fly ash with or without copper coating were prepared. Small cylindrical specimens of 9 mm diameter and 10.5 mm length were fabricated at 300 MPa using single action die compaction at ambient temperature. These compacts were sintered in argon atmosphere for a period of 45 min at 700°, 740°, and 780°C, respectively. The green and sintered properties of the compacts were determined as a function of fly ash weight percent. The results indicated that density, hardness, and compression strength of the green compacts were improved by the electroless copper coating on fly ash reinforcement. It was also observed that coated green compacts exhibited lower spring back and higher ejection pressures compared to uncoated compacts. Sintering resulted in increase in density and decrease in volume of green compacts. Sintered density of the composites was found to decrease with increasing weight percent of fly ash. It was further observed that sintering of coated composites resulted in higher densification, hardness and, compressive yield strength than uncoated composites. Dry sliding wear behavior of the sintered coated and uncoated fly ash composites was also carried out at room temperature using a pin-on-disc machine. Copper coated fly ash compacts exhibited better wear resistance than the matrix and uncoated fly ash compacts within the range investigated.