Metallic Multi-layer Bonds

Metallic bonds are either multi-layered (produced by sintering or infiltration) or single-layered (produced by electroplating or brazing) [MARI07]. They are only applied to superabrasive grits because conventional grits wear too quickly to use the bonding strength to full capacity.

1.3.1 Chemistry and Types of Metallic Bonds for Multi-layer Abrasive Tools

Metallic multi-layered bondings consist of various alloys such as copper/tin-bronze (Cu/Sn), cobalt-bronze (Co/Cu), tungsten carbides (W/WC) or alloys from the iron-copper-tin-system (Fe/Cu/Sn) [KLOC09, STOC86]. Common Cu/Sn alloys have a ratio of 85:15 or 80:20 Cu to Sn with fillers and additional alloys [MARI07, p. 122]. The binder needs to have good wettability for the abrasive grits.

Iron and iron consisting metals may cause undesired reactions with diamond grits [STOC86]. Diamond tools for stone drilling and sawing use bond systems based on tungsten, tungsten carbides, or cobalt alloys [STOC86, WEIS08]. Besides high wear resistance and toughness, tungsten builds an advantageous, small inter­face layer of tungsten carbide with the diamond grits [STOC86]. Therefore, the bond retention is not only mechanical but also chemical. Moreover, auxiliary metal powders on the basis of cobalt, nickel, copper, iron, and mixtures of copper-nickel — zinc, copper-zinc and copper-manganese optimize bond retention [STOC86].

Metallic bonds have strong grit retention and are wear resistant against the chips of brittle, short-chipping materials. The high hardness becomes a disadvantage in tool conditioning. Nevertheless, metallic bonds can be modified to be brittle and dressable, for example increasing the Sn content or adding Ag embrittles bronze bondings [MARI07, p. 122]. Co increases wear resistance.

Updated: 24.03.2016 — 11:54