Spraying power influence on microstructure and bonding strength of ZrSi2 coating for SiC coated carbon/carbon composites

The objective of this current paper was to characterize the ZrSi2 coating deposited on the SiC coated carbon/carbon (C/C) composites by supersonic atmospheric plasma spraying (SAPS) at different spraying power. The microstructure, phase composition and bonding strength were investigated. In the process of spraying, a few of ZrSi2 powders were quickly oxidized to produce ZrO2, SiO2 and ZrSiO4 ceramic phases. These phases were randomly embedded in the ZrSi2 coating to enhance the mechanical performances of the coating to some extent. In addition, t-ZrO2 and c-ZrO2 phases formed above 1473 K might be converted into m-ZrO2 accompanied with 8% volume expansion, which can heal part of microcracks of the ZrSi2 coating. Therefore, only a few micro cracks and pores at the spraying power of 40 kW were found at the surface of ZrSi2 coating and no penetrative cracks existed in the cross section. Meanwhile, the bonding strength of the interface between the ZrSi2 and the SiC coating reached up to 11 N at 40 kW. In short, the SAPS technology was deemed to be a useful method to deposit the ZrSi2 coating on SiC coated C/C composites with high performance.