Sealing of cracks in the rhenium coating on C/C composites by alloying with cobalt

• A new method of sealing cracks of the rhenium coating on C/C was proposed.
• Re–Co alloys acted as excellent adhesives sealed the cracks and inter-grain gaps.
• The bond strength of rhenium coating and C/C is weakened by modification.
• The rhenium coating free of cracks on the C/C substrates was acquired.

Thermal stress cracks of the rhenium coating on C/C composites have severely limited its applications. In the present work, rhenium coatings were prepared on C/C composites by chemical vapor deposition (CVD) and modified by alloying with cobalt. The results showed that the as-prepared rhenium coating consisted of monolayer columnar grains with significantly < 002 > preferred orientation, which led to lower ductility and mechanical strength in the coating. After modification, the cracks of the rhenium coating were sealed by rhenium–cobalt alloys and the ductility and mechanical strength of the coating had a remarkable improvement. Moreover, tensile and shear bond strength of the as-modified rhenium coatings with C/C substrates had a considerable reduction. The cobalt-modified rhenium coatings free of cracks were acquired on C/C composites ultimately.