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.

Research highlights▶ Controlled erosion is essential to the proper functioning of diamond composite tool materials, used for precision grinding of glasses and ceramics. In this study a design of experiments based methodology was used to study the erosion of bronze-bond, diamond-abrasive composites. ▶ Differences in erosion among composites with different bond designations were statistically significant, but small in magnitude. ▶ Erosion decreased with increasing diamond concentration and with increasing diamond size. A synergistic interaction between the diamond concentration and diamond size effects was also detected. ▶ Eroded surfaces were characterized by development of comet tails of bond material, protected by and supporting the protruding diamonds. Long, well-developed comet tails were observed in composites with diamonds much larger than the erodent. Shorter comet tails were detected for diamonds comparable in size to the erodent and no comet tails were produced for diamonds much smaller than the erodent. For high concentrations of large diamonds, overlapping of/interaction among comet tails was observed. ▶ Morphological differences on the eroded surfaces, and their dependence on the relative size of the diamonds compared to the erodent, provide the most plausible explanation for the observed diamond size and concentration effects. Well-bonded diamond particles, larger than the erodent, protect the bond material immediately behind them, producing a comet tail morphology and reducing erosion.