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 microcracks 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.