Study of thermal shock resistance of HVAF spraying thickness gradient WC-Cr3C2-Ni coating on crystallizer surface

The heat distribution and wear threat of the plate crystallizer used in continuous casting production are different in each area, and a single-thickness coating is unable to fulfill the requirements of all areas. To extend the service life of the crystallizer, a high hardness WC-Cr₃C₂-Ni thickness gradient wear-resistant coating was prepared on the inner wall of the crystallizer via the HVAF (High-Velocity Air Fuel) spraying technology. In cyclic thermal shock environments, the thermal shock resistance of planar coatings decreased with the thickness. The coating with a thickness of 100 μm exhibited the best thermal shock resistance, with up to 25 cycles at 800 °C thermal shock. In high-temperature wear experiments simulating actual service environments, the 300 μm coating, which owned the worst theoretical thermal shock resistance, was well bonded to the substrate and exhibited good serviceability. Comprehensive experimental results showed that the WC-Cr₃C₂-Ni coatings deposited by HVAF were stable in practical long-cycle production. The coating preparation process proposed in this paper has been applied in domestic steel mills, effectively extending the working cycle of the production line and improving economic efficiency. This study will provide a theoretical basis for the selection and preparation of surface coatings for continuous casting crystallizers and other structures in complex service environments.