Optimizing Micro–Nano Dual-Scale SiCp/6061Al Coatings via Plasma-Assisted Cold Spraying

To address issues such as weak interfacial bonding, low deposit thickness, and poor ductility in the preparation of micro-nano dual-scale silicon carbide particle reinforced 6061 aluminum matrix (SiCp/6061Al) composite coatings via cold spray technology, a plasma-assisted cold spray (PCS) technique was employed. By adjusting the plasma source power (16-40 kW), simultaneous heating of both the substrate and the injected particle stream was achieved. This process primarily leverages the synergistic effect of plasma induced thermal softening and helium/argon mixed gas thermal convection, effectively reducing the critical deposition velocity of the aluminum alloy particles and enhancing their plastic deformation capability. The results demonstrated that at 40 kW, the peak substrate temperature reached 252 °C, and the total coating thickness increased to 861.3 μm, corresponding to a 135% increase compared with unassisted cold spray (CS). The EDS results qualitatively showed a broader distribution of Si-containing regions in the coating cross-sections under plasma-assisted conditions. Furthermore, plasma assistance promoted particle deformation and coating densification, while the cross-sectional observations suggested fewer visible interfacial discontinuities in the examined regions. The proportion of low-angle grain boundaries decreased from 27.2% in CS to 13.6%, indicating optimized interfacial microstructure. In terms of macroscopic properties, the coating’s Vickers hardness reached 108 HV_0.5, a 20.8% improvement over CS. Rotational friction tests showed a 14.7% reduction in wear rate, a decreased friction coefficient, and a transition in the wear mechanism from composite delamination and abrasive wear to mainly mild abrasive wear, indicating significantly enhanced wear resistance. The shear strength also increased to 80.8 MPa. Consequently, the plasma-assisted cold spray technology, effectively resolves key technical challenges in fabricating aluminum alloy composite coatings via cold spray, significantly enhancing deposition thickness, microstructure, and mechanical and tribological properties.