Microstructure and Properties of Laser <i>In-situ</i> Synthesized Al₂O₃-TiO₂ Composite Ceramic Coating

Abstract

The study involves in-situ synthesis of CrFeAlTi composite coating using laser micro-melting processing. The coating was successfully prepared by laser irradiating CrFeAlTi coating prepared by flame spraying on the China low activation martensitic (CLAM) steel substrate, and then Al2O3-TiO2 composite ceramic coating was synthesized by in-situ reaction on the surface of flame sprayed coating. The coating morphology, microstructure, phase composition, micro-hardness, dry sliding wear properties and corrosion resistance in liquid PbBi alloy were analyzed by stereomicroscope, scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), micro-sclerometer, vertical universal friction wear testing machine and static PbBi corrosion test device, respectively. The test results show that the surface of Al2O3-TiO2 composite ceramic coating is smooth, and the microstructure of coating is both homogeneous and dense without defects such as crack, dimple and porosity, etc., a good metallurgical bonding between the composite ceramic coating and the substrate, and the interface is obvious. The phases of the coating surface are mainly composed of Al2O3, TiO2, (Al.948Cr.052)2O3, Fe2TiO5 and FeCr, etc. The coating shows a high average micro-hardness of approximately 1864.2HV0.2, which is about three times higher than that of the CLAM steel substrate, and presents gradient distribution with stable transition from the coating surface to the substrate. Comparing with the substrate, the coating presents excellent wear resistance. The wear mass loss of the coating is just one sixth of that of the substrate. Meanwhile, the coating exhibits the best corrosion resistance in the liquid PbBi.

Keywords

• flame spraying
• laser <i>in-situ</i> synthesis technology
• Al₂O₃-TiO₂ composite ceramic coating
• microstructure
• property