| NiCrAlY coatings, with the properties of excellent oxidation resistance,corrosion resistance and bonding performance, have been widely used in bonding layer as protective coating or thermal barrier coating(TBCs). There are many ways to fabricate NiCrAlY coating, but it is difficult to carry on for some workpieces of complex structure, such as u-shaped structure and pipe wall.However, electron spark deposition(ESD) can deposit the workpieces with various shapes. Therefore, this research mainly focused on the microstructure and anti-oxidation properties of NiCrAlY coating fabricated by the ESD method.NiCrAlY coatings were deposited on the surface of GH4169 by ESD method with different parameters. The NiCrAlY coating of best parameter was chosen according to the deposition law, the microstructures, phase composition,microhardness, binding force and isothermal oxidation properties. Results showed that the deposition rate of coating was increased with the increasing of voltage, while the effect of capacitance was slight. The microhardness of NiCrAlY coating fabricated under voltage of 100 V was slightly higher than thatder 150 V. The microhardness got maximum value of 475 HV when deposition voltage was 100 V and the capacitance was 40 ?f. For the binding force between the NiCrAlY coating and substrate, all NiCrAlY coatings were more than 80 N.In terms of isothermal oxidation property of the coatings, oxidation resistance of coatings was decreased with the increasing of the voltage. And the oxidation resistance of the coatings firstly decreased and then increased with the increasing of capacitance. Therefore, oxidation resistance property of the coating achieved optimal when deposition voltage was 100 V and capacitance was 120 ?f.Meanwhile, the thinner the coating was, the better the antioxidant effect reached.According to the different requirements of coating thickness in practical application, it was better to choose coatings with the thickness of 200 ?m. In conclusion, the optimal deposition parameters were the voltage of 100 V,capacitance of 120 ?f, thickness of 200 ?m.The research of isothermal oxidation property and cyclic oxidation property in 850 ?, 900 ?and 1000 ? was performed by choosing NiCrAlY coatings with the optimal parameter i.e. voltage of 100 V, capacitance of 40 ?f and thickness of200 ?m. In terms of isothermal oxidation, oxidation rate constant of the coating increased gradually and its oxidation resistance decreased gradually with the increasing of isothermal oxidation temperature. Al2O3 content and the thickness of the film were increased with the extending of oxidation time; the oxide film of coating got thick, the micro-crack of surface oxidation film was increased and the?-Al2O3 was gradually transformed to ?-Al2O3 with the increasing of oxidation temperature. In terms of oxide film's binding force to the coating, the level of bonding force were greater than HF3 and the oxide film of this level had a good protectiveness for coating.In the process of cyclic oxidation, when the number of cycle was at the same,the higher oxidation temperature, the serious oxidation film peeling. And when oxidation temperature was same, the more cycle was, the thicker oxide film was and the more oxidation film peelled. The main component of coating oxide film was Al2O3. For the binding force of the oxide film and coating, the worst level was HF3, which means that it had a good protectiveness for coating. |
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