The Preparation Of Oxide-Ni Laminated Coating By Wet Chemical Method And Its High-Temperature Oxidation Resistance

The preparation of protective coating under the surface of the steel is one of the major method to reduce oxidation of steel under elevated temperature service condition. Oxide coating, the commonly used protection coating under high temperature, are easily cracking and spalling under the thermal stress due to the mismatch of thermal expansion coefficient with substrate which can shorten the oxide coatings service life. In order to improve the spallation and oxidation resistance, the metal coating with good plasticity and toughness can be utilized with the oxide coating to prepare the oxide-metal micro-laminated coating. The preparation of the oxide-metal micro-laminated coating with simple and low-cost method is of certain practical significance.The YSZ-Ni, Al2O3-Ni, YSZ-Al2O3-Ni micro-laminated coating were prepared on the surface of the 304 stainless steel and T91 steel with the sol-gel and electroless nickel plating method. And the effects of the oxide coating thickness, nickel coating thickness and the position of Ni coating in the oxide coating on the high temperature oxidation resistance of the as-prepared micro-laminated coatings were studied.The surface and cross-section morphology of the micro-laminated coating were characterized by SEM. The EDS was also used to detect the surface composition of as-prepared samples. Besides, phases of the prepared coatings were analyzed by X-ray diffraction. The results indicated that smooth, dense and crack-free oxide-nickel micro-laminated coating were successfully prepared with sol-gel and electroless nickel plating method on the surface of substrate stainless steel and T91 steel. The thickness of nickel coating and oxide coating are approximately 130nm and 170nm respectively for the Z16N1 oxide-nickel micro-laminated coating. What’s more, the Zr0.98Y0.08O1.96, Y-Al2O3 and amorphous nickel are identified in as-prepared coating.The high-temperature oxidation test of laminated coating composed of different oxide coating thickness, nickel coating thickness and position of nickel coating were carried out with the cyclic oxidation weight gain method, the surface morphology of which were also characterized by the Laser scanning confocal microscope. The results revealed that the sample coated with oxide-nickel micro-laminated coating perform better high temperature oxidation property than the one coated with oxide coating. Moreover, for the YSZ-Ni and Al2O3-Ni micro-laminated coatings with the same structure, the former have better high temperature oxidation property. The high temperature oxidation property of the YSZ-Al2O3-Ni composite micro-laminated coatings are better than the YSZ-Ni and Al2O3-Ni coating. For the sample coated with nickel coating of same thickness, the oxidation weight gain and spallation decrease with the oxide coating thickness and the surface condition become better. For the sample coated with same numbers of oxide coating, the oxidation weight gain and spallation of increase with nickel coating thickness and the surface condition become worse.For the sample coated with oxide and nickel coating of same thickness, the sample with the nickel coating between oxide coatings perform better high temperature property than the one with the nickel coating as the outermost layer.