Influence of the powder metallurgy route on the mechanical properties of Cu–Cr–diamond composites

Abstract

Metal-bonded grinding tools are commonly based on copper as bond material and possess low porosity. The powder metallurgic fabrication and the applied process parameters have a high influence on the mechanical properties of these grinding layers. In this study, Cu–diamond composites are fabricated through Field Assisted Sintering Technology with a variation of holding time, temperature, pressure, and chromium powder particle size. The addition of chromium to these composites can ensure a higher adhesion of the diamonds through carbide formation within the interface of the diamonds and the copper bonding matrix. The coating of diamond with chromium-carbide is mainly controlled by the chromium powder particle size, which leads to a higher critical bond strength with decreasing particle size. Maximum critical bond strength of 463 N/mm2 is reached using chromium with an average particle size of 10 µm. Increasing holding time decreases porosity and increases the critical bond strength of the composites. An increase of sintering temperature from 900 to 1040 °C leads to a decrease of porosity due to local melting of the copper. The interlocking of diamonds due to their high concentration of 50 vol% within the composites results in a relatively high porosity above 7%.