Oxidation behavior of (Mo,W)Si2–Si3N4 composite coating on molybdenum substrate at 1600 °C

作者：Houan Zhang; Jianxian Lv; Yihui Wu; Siyong Gu; Yu Huang; Ying Chen

来源：Ceramics International, 2015, 41(10, Part B): 14890-14895.

• B. Electron microscopy
• C. Diffusion
• D. Silicides
• Oxidation

(Mo,W)Si2–Si3N4 composite coating on pure molybdenum (Mo) substrate was prepared by using in situ diffusion of tungsten (W), nitrogen (N) and silicon (Si) elements. The microstructures and phase compositions were investigated using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). A coarse columnar crystal structure was observed in the original dense (Mo,W)Si2–Si3N4 layer in the SEM micrographs. The transition layers of (Mo,W)5Si3 and (Mo,W)3Si were formed between the coating and Mo substrate during a oxidation process at 1600 °C in air. The growth kinetics of (Mo,W)5Si3 transition layer in (Mo,W)Si2–Si3N4 coating obeyed a parabolic rate law and its growth rate constant was 7.22×10−10 cm2/s. The strong hindering effect of W element in coating on the Si diffusion led to a longer antioxidation life of the (Mo,W)Si2–Si3N4 coating on Mo substrate at1600 °C.