Fabrication and evaluation of electroplated Ni–diamond and Ni–B–diamond milling tools with a high density of diamond particles

Ni–diamond and Ni–B–diamond composite deposits were electroplated with a current density of 20 A/dm² on a steel cylinder with a diameter of 6.0 mm in a Ni-Watt bath with different tetramethylammonium borohydride (TMAB) concentrations and 300-g/L synthetic diamond particles with sizes between 30 and 50 μm. Prior to Ni–diamond or Ni–B–diamond composite electroplating, a Ni undercoating with a thickness of 50 μm was electroplated on the steel cylinder. During composite electroplating, diamond particles were intermittently stirred with different stirring cycles in the plating bath. Experimental results show the distribution of diamond particles in the Ni or Ni–B deposit depends strongly on the stirring cycle. A composite deposit with a high diamond density can be achieved with intermittent stirring by using an on the period of 5 s and an off period of 80 s. From the results of milling test, an electroplated Ni–B–diamond milling tool with a high milling ability can be achieved after annealing at 300 °C or 500 °C for 30 min.