Oxidation and cracking/spallation resistance of ZrB2-SiC-TaSi2-Si coating on siliconized graphite at 1500 °C in air

A ZrB2-SiC-TaSi2-Si coating on siliconized graphite substrate was prepared by a combination process of slurry brushing and vapor silicon infiltration. The high-temperature oxidation behavior and cracking/spallation resistance of the as-prepared coating were investigated in detail. It was revealed that the oxidation kinetics at 1500 degrees C in static air followed a parabolic law with a relatively low oxidation rate constant down to 0.27 mg/(cm(2).h(0.5)). The crack area ratio of the as-prepared coating was determined as 3.8 x 10(-3) after severe thermal cycling from 1500 degrees C to room temperature for 20 times. Apart from the formation of ZrO2 as skeleton phase with SiO2 as infilling species, the good oxidation and cracking/spallation resistance of the coating also could be attributed to its unique duplex-layered structure, i.e., a dense ZrB2-SiC-TaSi2-Si major layer filled with Si and an outermost Si cladding top layer. Meanwhile, the strong adhesion strength of the SiC transition layer with the graphite substrate and the outer ZrB2-SiC-TaSi2-Si layer was a vital factor as well.