High temperature protection of a novel TiB2-modified (Nb,Mo,Cr)Si2 ceramic coating on Nb-based alloy

In order to solve the challenge of poor protection of conventional NbSi2 coatings in high temperature oxidation environments, a new TiB2-modified (Nb,Mo,Cr)Si2 composite ceramic coating was prepared on the surface of Nb521 substrate by triple slurry sintering method. The composite ceramic coating maintained the complete morphology after oxidation at 1600 ℃ for 15 h, due to the oxide layer TiO2-(Ti0.6Cr0.2Nb0.2)O2-SiO2 formed on the coating surface, which could effectively reduce the volatilization behavior of SiO2 and prolongue the oxidation life of the coating by wrapping the SiO2 layer. In addition, the coating successfully withstood 1500 cycles from room temperature to 1600 ℃, due to the fact that CrSi2 and MoSi2 significantly modulated the difference in thermal expansion coefficients between the Nb521 substrate and the NbSi2 coating, making the thermal stress generated during the thermal shock cycle lower than the intrinsic strength of the coating.