Duplex NiP/NiMo-(h)BN Co-Electroplating: Evaluation of Nanohardness, Room and High Temperature Wear Behaviors

This study presents the development of duplex NiP/NiMo-(h)BN co-electrodeposit applied to steel substrates using a reverse pulsed current (PC) deposition technique. The (h)BN was synthesized in a two-dimensional nanosheet structure via metallothermic reduction in molten salt. Duplex electrodeposition provide improved physical and mechanical characteristics over single-layer plating, making them suitable for applications requiring enhanced wear and adhesion properties. Here, NiP was selected as the inner layer due to its strong adhesion to steel, while NiMo-(h)BN served as the outer layer to maximize wear resistance. Both NiP and NiP/NiMo-(h)BN electrodeposits were deposited using a reverse pulsed current approach to enhance high temperature wear resistance of the steel substrate. Incorporating (h)BN nanosheets into the NiMo matrix significantly improved the deposit's nano-hardness, raising it from 4.26 GPa to 5.23 GPa with the addition of 10 g/L (h)BN. Additionally, the solid lubrication properties of (h)BN reduced the friction coefficient of the duplex electrodeposit from 0.7 to 0.4 µ. At 400 °C, the wear rate of the duplex NiP/NiMo-(h)BN co-electrodeposit was measured at 1.77 x 10⁻⁵ mm³/Nm, demonstrating nearly twice the wear resistance compared to the duplex NiP/NiMo alloy deposit.