▎ 摘　　要

NOVELTY - Preparation of multi-stage hard coating involves preparing component (A) using silver nitrate, graphene oxide and unsaturated polyester resin solution, uniformly applying component (A) on surface of a metal substrate, curing, placing substrate in a vacuum chamber, supplying argon gas, turning on magnetron sputtering power source, depositing titanium nitride coating on the surface, depositing an aluminum-titanium nitride coating on surface, stopping introduction of argon after completion of deposition, turning off the power, taking out the substrate and drying obtain hard coating. USE - Preparation of multi-stage hard coating (claimed). ADVANTAGE - The method enables preparation of multi-stage hard coating having excellent uniformity and adhesiveness with substrate. The coating film has excellent crack resistance, oxidation resistance and peeling strength, and does not fall off. DETAILED DESCRIPTION - Preparation of multi-stage hard coating involves adding 2-3 g silver nitrate to a beaker, adding 100-150 mL deionized water, stirring with a glass rod to completely dissolve solid, adding 300-500 mL n-butanol to the beaker, stirring, transferring the obtained mixture to a three-necked flask, placing in an oil bath, heating to 55-60 degrees C, adding 0.8-1.2 g graphene oxide as portions to the beaker, heat-preserving, stirring for 1-3 hours, obtaining a reaction solution, adding 500-700 mL sodium hydroxide solution having pH of 9-9.5 and 2-2.2 g sodium borohydride to the solution, stirring, mixing for 30-50 minutes, slowly dripping aqueous sodium borohydride solution in the obtained solution, such that the solid-liquid ratio of reactants and aqueous sodium borohydride solution is 1:2, heating oil bath to 117-118 degrees C, stirring for 1-3 hours, obtaining a residue, washing with deionized water 2-4 times, drying in an oven at 60-80 degrees C for 10-15 hours, pulverizing the dried product, sieving to obtain 200-300 mesh powder, mixing the obtained powder with an unsaturated polyester resin solution with solid-liquid ratio of 1:2, ultrasonically dispersing the resultant product for 5-10 minutes, obtaining a component (A), taking a metal substrate, polishing surface of the substrate in a polishing machine, immersing the polished metal substrate in acetone, ultrasonically cleaning for 5-10 minutes, cleaning the surface with deionized water 2-3 times, drying cleaned metal substrate in a vacuum drying box, uniformly applying component (A) on the surface of the dried metal substrate, curing at room temperature, placing substrate in a vacuum chamber immediately after completing 80% curing, supplying argon gas at a vacuum of 10-4 to 10-2 Pa, turning on magnetron sputtering power source, depositing titanium nitride coating on the surface at 200-400 degrees C, under discharge current of 20-30 A and bias voltage of -80 V to -20 V for 3-5 minutes, depositing an aluminum-titanium nitride coating on surface at 500-700 degrees C, under current of 50-100 A and bias voltage of -150 V to -50 V for 5-10 minutes, stopping introduction of argon after completion of deposition, turning off the power, taking out the substrate and drying in oven at 60-80 degrees C for 5-6 hours to obtain hard coating.