Abstract
Tungsten (W) and molybdenum (Mo) were coated on silicon carbide (SiC) as refractory armor using high power plasma arc lamp at powers up to 23.5 MW/m2. Both W powder and Mo powder were melted and formed coating layers on SiC. The effect of pretreatment (vapor deposition of titanium (Ti), W and Mo and annealing) and sample heating conditions on microstructure of the coating and coating/substrate interface were investigated. The microstructure was observed by scanning electron microscopy (SEM) and optical microscopy (OM). A strong W coating was successfully formed. Tungsten vapor deposition and pre-heating at 5.2 MW/m2 made for a refractory layer containing no cracks which propagated into the SiC substrate. This layer was formed without the thick reaction layers (WC and W5Si3) reported in previous studies. Moreover the thinner interface transition layer and armor avoid coefficient of thermal expansion (CTE) mismatch driven failure previously reported. For this study, small WC grains were observed adjacent to interface. Silicon carbide grains and W5Si3 grains were observed within W coating. By contrast, Mo was not formed as well as W due to larger CTE mismatch than that for W and SiC.
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