Design and preparation of MoSi2/SiO2-Nb2O5/NbSi2 multilayer coating on Nb alloy: Microstructure and hot corrosion behavior

A MoSi 2 /SiO 2 -Nb 2 O 5 /NbSi 2 multilayer coating was designed on Nb alloys using halide activated pack cementation (HAPC) and an innovative liquid plasma-assisted particle deposition and sintering (LPDS) method to improve its hot corrosion resistant. The weight gain of MoSi 2 /SiO 2 -Nb 2 O 5 /NbSi 2 coating was 3.204 mg/cm 2 after 200 h, which was 85.7% lower than that of NbSi 2 /Nb 2 O 5 -SiO 2 coating, while the life of NbSi 2 coating was restricted only 100 h (20.539 mg/cm 2 ) at 900 °C in Na 2 SO 4 +NaCl salt. This improved performance is attributed to the prefabricated SiO 2 -based barrier layer and MoSi 2 as a Si source to supplement the SiO 2 content, thus effectively alleviating the penetration of oxygen and molten salts. • A new type of MoSi 2 /SiO 2 -Nb 2 O 5 /NbSi 2 multilayer coating is designed to resist hot corrosion. • The multilayer coating is fabricated by combining halide activated pack cementation and an innovative liquid plasma-assisted particle deposition and sintering method. • The MoSi 2 /SiO 2 -Nb 2 O 5 /NbSi 2 multilayer coating shows superior hot corrosion resistance. • The pre-fabricated MoSi 2 /SiO 2 -Nb 2 O 5 layer is a barrier against molten salt and oxygen, in which the MoSi 2 acts as a Si source to consume oxygen and replenish the SiO 2 .