One-step fabrication of double-layer nanocomposite coating by plasma electrolytic oxidation with particle addition

A novel double-layer structural nanocomposite coating was prepared via one-step plasma electrolytic oxidation-synchronous deposition & sintering of nanoparticles (PEO-SDSN) technique under unique threshold conditions of concentration of added nanoparticles, electrolyte temperature, and applied voltage. The special discharges at the coating/electrolyte interface lead to the directional migration, deposition and sintering of organic (eg. PTFE) or inorganic (eg. SiC) nanoparticles, combined with the dynamic growth equilibrium of bottom oxide layer and outer nanoparticle deposition & sintering layer. Different from traditional PEO, the addition of nanoparticles creates interesting rising and falling changes in current and corresponding discharging characteristics. The underlined formation mechanism of the double-layer coating was detected by OES combined with discharging phenomena and coating structure evolution. Moreover, compared with the single PEO coating, the double-layer structural nanocomposite coating has better comprehensive performances, such as corrosion protection, and low and stable friction coefficient. The PEO-SDSN technique is energy saving, more importantly, it provides a brand-new fabrication strategy for a series of double-layer multifunctional coatings by tailoring the nanoparticles species. Eventually, the potential applications and guiding strategies of double-layer nanocomposite coating are presented.