Multilayer synergistic design of NbSi2/Nb2O5-SiO2/MoSi2 ceramic coating on niobium alloys for multiple thermal protection properties

A novel NbSi2/Nb2O5-SiO2/MoSi2 multilayer thermal protection ceramic coating is designed and fabricated via halide-activated pack cementation and liquid-plasma-assisted particle deposition and sintering technology, endowing the coating with multiple high-temperature protective properties. The incorporation of MoSi2 nanoparticles not only gives superior high-temperature oxidation resistance/hot corrosion resistance of coating by forming a dense SiO2 barrier layer, but also promotes passive radiative heat dissipation. When NbSi2/Nb2O5-SiO2/MoSi2 coating was prolonged exposure to air at 1250 °C for 50 h of oxidation and at 900 °C for 100 h of corrosion, the mass gains are only 0.37 mg/cm2 and − 0.52 mg/cm2, respectively. The multilayer coating exhibits enhanced emissivity (>0.88) over the thermal infrared range of 3–20 µm, due to the lattice vibrational absorption-matching synergy of Nb2O5, SiO2, and MoSi2, as well as the mutual doping of SiO2/Nb2O5, mismatch of atoms at the interface, and a high degree of lattice distortion within the coating.