Fabrication and microstructure of ZrB2-ZrC-SiC coatings on C/C composites by reactive melt infiltration using ZrSi2 alloy

摘要

ZrB2-ZrC-SiC ternary coatings on C/C composites are investigated by reactive melt infiltration of ZrSi2 alloy into pre-coatings.Two different pre-coating structures,including porous B4C-C and dense C/B,are designed by slurry dip and chemical vapor deposition(CVD)process respectively.The coating prepared by reactive melt infiltration(RMI)into B4C-C presents a flat and smooth surface with a three-1ayer cross-sectional structure,namely interior SiC transition layer,gradient ZrB2-ZrC-SiC layer,and ZrB2~-ZrC exterior layer.In comparison,the coating prepared by RMI into C/B shows a more granular surface with a different three-1ayer cross-sectional structure,interior unreacted B-C pre-coating layer,middle SiC layer,and exterior ZrB2-ZrC-ZrSi2 layer.The forming mechanisms of the specific microstructures in two coatings are also investigated and discussed in detail.