Synergistic Optimization of Heterogeneous Interface Bonding and Surface Performance of 316 Stainless Steel Coatings Deposited on 7050Al Alloy Substrates via Laser-Assisted Cold Spray

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Abstract
The fabrication of aluminum/steel heterogeneous metals is challenging due to interfacial cracking from brittle intermetallic compounds produced in high-heat-input processes and poor heterogeneous interfacial bonding in cold spray (CS). In this work, laser-assisted cold spray (LACS) was used to deposit 316 stainless steel (316SS) coatings on 7050Al substrates, and the microstructure and properties were systematically investigated. An L9(3³) Taguchi design was first employed to optimize the CS parameters, followed by an evaluation of the effect of laser power on coating performance. The results showed that 600 W was the optimal laser power, reducing the coating porosity from ~1.0% to 0.2%. Laser irradiation also markedly improved heterogeneous interfacial bonding, increasing the bond strength from 35 MPa for CS coatings to over 65 MPa. X-ray diffraction confirmed that LACS retained the characteristics of solid-state deposition, with only γ-Fe detected and no δ-Fe or Al-Fe intermetallic compounds formed. EBSD analysis showed that LACS promoted grain refinement, substructure evolution, and grain boundary transformation, leading to a more homogeneous microstructure. In addition, compared with CS coatings, LACS coatings exhibited superior wear and corrosion resistance, with the friction coefficient decreasing from 0.75 to 0.65, the wear rate dropping from 7.5 × 10⁻⁴ to 7.2 × 10⁻⁵ mm³·N⁻¹·m⁻¹, and the corrosion current density decreasing from 2.71 × 10⁻⁵ to 8.77 × 10⁻⁶ A/cm². These results demonstrate that LACS provides an effective solid-state route for fabricating high-performance 316SS/7050Al heterogeneous coatings.

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