Erosion and surface structure development of metal–diamond particulate composites

Metal-matrix/diamond-abrasive composites are commonly employed in precision grinding of glasses and ceramics. Erosion, to replace worn diamond cutting points, is essential to proper tool functioning. However, the erosion behavior of these materials has not been well characterized or understood. In this study, the results of experiments on bronze-matrix, diamond-abrasive composite tool materials are described. The effects of systematic changes in the metal-matrix (“bond hardness” and measured mechanical properties) and diamond particles (size and concentration) on both the erosion rate and surface structure of the composites at different angles of attack were studied using a design of experiments approach. The composites exhibited ductile erosion behavior, characterized by an increase in erosion as the angle of attack was decreased. Changes in the metal-matrix produced statistically significant but relatively small effects. However, changes in diamond size and concentration strongly affected both the rate of erosion and the morphology of the eroded surface. Diamond particles smaller than the erodent had little protective effect. In contrast, diamond particles larger than the erodent protected the bond material immediately behind them, producing a comet tail structure and reducing erosion. The resultant surface morphologies closely resemble those produced during precision grinding of glasses and ceramics.