Ceramic materials are widely used in aerospace, mechanical parts and other fields due to their high temperature bending strength, thermal insulation, wear resistance, corrosion resistance and excellent mechanical properties.Thermal spraying technology has been widely used in the preparation of ceramics, metals and amorphous coatings because of its high flame temperature, fast flame flow and fast droplet cooling. Thermally sprayed ceramic coatings provide excellent protection of metal substrates. For example, ceramic coatings applied by thermal spraying have good self-strengthening heat insulation performance under high temperature environments, good thermal cycling ability under thermal cycling, good anti-crack growth under internal stress in high temperature environments, and good anti-ablation under continuous high temperature environments. Among these materials, Al2O3–TiO2 ceramics have good wear resistance and excellent mechanical properties, which are widely used in wear part surfaces . Because the thermophysical properties of ceramic top-coats and metal substrates are quite different, the alloy bond-coats are prepared between top-coats and substrates to reduce its stress gradient. However, the crack propagation of the interface between top-coats and bond-coats becomes the main mechanism of failure during the service of thermal spraying coatings. The bond and durability of the bond-coats and top-coats interface determines the service life of the whole material. Many studies have been conducted to improve the bond between the bond-coats and top-coats interfaces. The adhesion and cohesion of plasma sprayed ceramic coatings were improved by high strength adhesive infiltration. A more direct method is to machine texture the surface of the bond-coats, changing the stress state of the metal-ceramic interface and improving the durability of the interface. Furthermore, the bonding property of the interface was further improved through heat treatment and interfacial reaction. In addition, many studies have been conducted on the bond-coats material. The unique structure and properties of amorphous materials was used to improve the interfacial bond, and the excellent mechanical properties of nanoparticles were used to enhance the interfacial strength. Moreover, the interface structure design of the bond-coats and top-coats was also studied. The interface between the bond-coats and top-coats was indistinct by a continuous gradient transition zone, the stress gradient near the interface was further reduced, and the mechanical properties of the interface were obviously improved. These studies have greatly improved the mechanical properties of the metal-ceramic interface, but the interface is still the weakest area of the whole material system, which determines the service life of the whole material and is still a hot topic in research. When the thermal spray coating is subjected to force during service, the direct cause of the formation and expansion of the interface crack is the difference in the mechanical properties between the metal and ceramic coating. This study takes advantage of the fact that FeCrAl alloy is prone to form oxides in defects and cracks at high temperatures. An Al2O3-40 wt% TiO2 ceramic coating was prepared on the surface of the FeCrAl alloy bond-coats prepared by arc spraying and heat treated in a hypoxic atmosphere to improve the difference in the mechanical properties between the metal bond-coats and the ceramic top-coats to improve the interfacial adhesion of the coating. After heat treatment, the coating formed an obvious, continuous elastic modulus gradient from the substrate to top-coats, and the interfacial adhesion was significantly improved.
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