Enhanced particle incorporation for co-electrodeposited Ni–P/diamond coatings with a pulse-stirring technique

Abstract

This study focuses on a fabrication technique that enhances diamond particle incorporation in nickel-phosphorus/diamond (Ni–P/diamond) composite coatings. Direct current co-electrodeposition with pulse-stirring was employed. Scanning electron microscopy (SEM) revealed nodular structures in the Ni–P/diamond composite coating. Cross-sectional analysis and energy dispersive X-ray spectroscopy (EDS) were used to quantitatively compare the amount of diamond particles, P content and Ni content in the composite coatings fabricated using different stirring cycles and current densities. Pulse-stirring was found to yield a multilayer structure and a higher amount of deposited diamond particles. Repeated off- and on-stirring patterns allowed the diamond particles to deposit through gravitation-assisted electrodeposition, while the short cycles of system agitation allowed diamond particles sedimented outside the coating area to become redispersed with a greater likelihood of incorporation into the coatings. The Vickers hardness test was performed to measure the hardness of the obtained composite coatings. The pulse-stirring sample fabricated using a 0.03 A/cm2 current density was shown to have a maximal hardness value of 912 ± 10.94 HV0.1. This accounted for a 17.82 % increase in hardness compared to that of a sample prepared using continuous stirring. Higher diamond content in the sample fabricated by the pulse-stirring technique also exhibited highest wear resistance and lowest friction coefficient.

Keywords

• Ni–P/Diamond coating
• Co-electrodeposition
• Hardness
• Tribological properties