Delamination of top layer splats as the predominate cavitation failure of HVOF sprayed coatings

Delamination of top layer splats as the predominate cavitation failure of HVOF sprayed coatings

Haijun Zhang, Xiuyong Chen, Hua Li*

Key Laboratory of Marine Materials and Related Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China. *: lihua@nimte.ac.cn.

The cavitation behaviors of HVOF sprayed WC-10Co4Cr coatings, Co-based alloy coatings, Fe-based amorphous/nanocrystalline coatings and WC-10Co4Cr/Co-based alloy composite coatings were typically investigated. The aim of this study was to figure out the controlling factors that dominate the anti-cavitation performances of thermal sprayed coatings. The properties of the coatings such as porosity, hardness, and elastic modulus were assessed. Changes in polished cross-sectional morphologies of the coatings during the cavitation testing were monitored by electron microscopy. The cavitation testing was continuously carried out for 256 hours. Results showed formation of microcracks during the testing, and the cracks propagated along splats¡¯ interfaces. When the transverse and the longitudinal cavitation cracks intersected within the coatings, peeling off of splats was seen as the major cavitation failure. Influence of other key variables of the coatings on their anti-cavitation performances was also elucidated. The results provide certain insight into selecting appropriate materials for thermal spray construction of anti-cavitation coatings with desired microstructures for long-term applications.