PC-SiC coating
To relieve the thermal mismatch between the top-coating and substrate, the SiC coating was first obtained as a buffer layer on the C/C substrate surface. The preparation procedures of SiC coating hasbeen reported in previous literature Schematic illustration of preparation process for PC-LMS and SAPS-LMS coatings is shown in Fig.1, and the concrete steps are described in detail subsequently.
The PC-LMS coating was prepared by pack cementation using LaB6(5-15wt%), MoSi2(50-70 wt%), SiC(20-30 wt%) and Al203(5-10wt%) as the precursor powders. Firstly, the feedstock powder was milled for 2-4 h to obtain a homogeneous mixture. Secondly, the pre-treated substrate was buried in the mixed powder in a graphite crucible, then the crucible was put into a graphite furnace. The furnace was heated to 2173-2373 K, and held for 2-4 h in Argon atmosphere.When the furnace temperature was naturally cooled to ambient temperature, the specimen was taken out from the crucible to obtain the PC-SiC coating.
Fig. 1. Schematic preparation procedures of the LMS/SiC coating by PC and SAPS methods
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