Study on electroless composite plating for an NiP bond micro diamond wheel

In this paper, nickel phosphorous diamond (Ni-P-D) composite plating is introduced as a new method to fabricate a micro diamond wheel with a diameter of φ450 μm. In the fabrication process, the steel substrate (SKD-11) is first ground to a ball end shape with a radius of 200 μm. Nickel phosphorous (Ni-P) and micro diamond particles with an average grain size of 3.5 μm are then electrolessly plated on the steel substrate tip, with a final plating thickness of approximately 25 μm. Parameters of the Ni-P-D plating conditions, including substrate rotation, stirring speed, and diamond grain density are then investigated. The topography of the micro wheel shows that diamond grains as the reinforced phase are embedded omnidirectionally and uniformly in the Ni-P plating along both the surface direction and the thickness direction. Energy dispersive spectrometer (EDS) results indicate that the ratio of diamond grains is approximately 27 wt%, and the Ni-P plating layer is an alloy in the amorphous state. Once fabricated, the micro diamond wheel performance is tested by grinding microgrooves on single crystalline silicon. The machined microgroove has a surface roughness of Ra 26 nm without obvious cracks. Micro tool wear after grinding proves that the bonding strength between diamond grains and Ni-P alloy, as well as the adhering strength between the Ni-P plating and steel substrate, are strong enough to meet the requirements of the micro grinding wheel.