High temperature oxidation and microstructure of MoSi 2 /MoB composite coating for Mo substrate

Abstract The two-layer MoSi 2 /MoB composite coatings were developed using the halide activated pack cementation (HAPC) method on Mo substrate. Oxidation resistance property and microstructural evolution of the coatings at high temperatures were investigated. During oxidation exposure, the coatings exhibited a good oxidation resistance property. The mass gains of the coated specimens oxidized at 1200 °C for 100 h and at 1300 °C for 80 h were 0.270 and 0.499 mg/cm 2 , respectively. Compared with the monolithic MoSi 2 coatings, the transformation of MoSi 2 phase in the MoSi 2 /MoB composite coatings was more sluggish at elevated temperatures. The growth rate constant of the Mo 5 Si 3 layer in the composite coatings was two orders of magnitude lower than that of the Mo 5 Si 3 layer in the monolithic coatings at 1300 °C. The microstructural degradation of MoSi 2 in the composite coatings at high temperatures was slowed by the introduced MoB layer. The MoB layer in the composite coatings is useful to prolong the service life of MoSi 2 coatings at high temperatures.