Abstract
Abstract
Micron silicon nitride (Si3N4) particles are less expensive than nano silicon nitride particles. Therefore, by adjusting the ratio of micron to nano particles, can a Ni-Co composite coating with excellent overall performance be obtained while controlling cost? This study introduced mixed nano and micron Si3N4 particles with different mass ratios. Ni-Co-Si3N4 composite coatings were fabricated via pulse electrodeposition. The influence mechanisms of single-scale and mixed-scale particles on the microstructure, corrosion resistance, mechanical properties, and wear resistance of the coatings were investigated. Results show that nano-Si3N4 particles exhibit a stronger tendency for co-deposition in the plating solution. They effectively refine grains and increase dislocation density, thereby significantly enhancing the wear resistance and mechanical properties of the coatings. The proportion of nanoparticles increased. The average grain size of the coatings refined from 16.60 nm to 12.31 nm. The dislocation density increased from 0.0046×10¹⁸ m⁻² to 0.0083×10¹⁸ m⁻².Accordingly, the microhardness increased from 365.9 HV to 533 HV. The average friction coefficient decreased from 0.72 to 0.51, and the wear rate significantly reduced from 31.65×10⁻⁹ mm³/N·mm to 2.27×10⁻⁹ mm³/N·mm. However, the introduction of nano particles led to an increase in surface roughness and a decline in corrosion resistance. Micron particles exhibited certain advantages in reducing surface roughness and improving corrosion resistance. The coating prepared under this condition achieved a maximum charge transfer resistance of approximately 415490 Ω·cm². In this study, the product method of specific wear rate and self-corrosion current density was used to calculate the overall performance. The S4 sample exhibited the optimal overall performance.