Fabrication and evaluation of electroplated diamond grinding rods strengthened with Cr-C deposit

Cr-C-Ni-diamond composite deposits with synthetic diamond particles of 50 μm in average size were electroplated onto a medium-carbon steel rod to fabricate electroplated diamond grinding rods. To make an electroplated Cr-C-Ni-diamond grinding rod with a high diamond density, three sequential electroplating processes were proposed, including Ni undercoating, Ni-diamond co-electroplating, and Cr-C strengthen-electroplating. The Cr-C strengthening deposit was prepared in an eco-friendly Cr³⁺-based plating bath. A composite Cr-C-Ni-diamond deposit with multi-layered diamond particles could be prepared on the steel rod substrate by repeating the proposed three sequential electroplating processes. After electroplating, some of the prepared grinding rods were annealed at 500 °C for 30 min to increase the hardness of Cr-C deposit. As-plated and annealed electroplated Cr-C-Ni-diamond grinding rods with one- and two-layered diamond particles were used to grind slots in Al₂O₃ plates in a depth of 5 mm to evaluate their grinding-life performances. Based on the results of grinding tests, the ground length of an electroplated Cr-C-Ni-diamond grinding rod was significantly increased after annealing at 500 °C for 30 min, and the length was further extended by electroplating two layers of Cr-Cs-Ni-diamond composite deposit. A relatively long ground length of 1320 mm was achieved from the 500 °C-annealed electroplated diamond grinding rod with two-layered diamonds, but only 30 mm from the as-plated one. It was evidenced that an anneal-hardened Cr-C deposit can serve as a competent strengthening layer in the electroplated diamond tool.