Effect of Current Density on Hardness of Ni-P/Diamond Composite Coatings Fabricated by Electrodeposition

Abstract

Nickel-Phosphorous/diamond coatings were electrodeposited onto steel substrates using a pulse-stirring method. The electrodeposition process involved a solution containing nickel sulphate, phosphorus acid, and diamond particles, resulting in the co-electrodeposition of 4-8 µm of diamond particles into a Ni-P matrix. To investigate the effects of electrodeposition current density on the properties of the Ni-P/diamond composite coating, scanning electron microscopy (SEM), hardness testing, and electrochemical testing were employed. The research findings revealed that higher current density (0.03 A/cm2) led to a denser diamond particle coating with diamond contents of up to 32.70 vol%. Additionally, the Ni-P/diamond coatings achieved a maximum hardness of 2819 ± 12.55 HV0.1 when fabricated using the current density of 0.03 A/cm2. The "pulse-stirring fabrication" method yields a coating with significantly enhanced wear resistance due to incorporating densely packed diamond particles. The intermittent pulses during the fabrication process are crucial for achieving the desired dispersion and adhesion of the diamond particles, leading to a practical and durable wear-resistant coating.