The Preparation Of Ni-Al Inter-metallic Thermal Barrier Coatings With Compound Plating In Water-based System

The plain steel (A3) is one of most widespread applying structural materials, but it cannot be used in some harsh environment because its corrosion resistance, particularly bad high temperature corrosion resistance. The current one kind of high temperature protective covering used widespread is the aluminum oxide coatings with the good high temperature antiseptic property, the wear resistance and the impact resistance and it may be used long-term in environment medium such as acid, alkali, salt mist and high-temperature oxidation, chlorination, nitridation, carbonization and so on. Because the aluminum oxide is often big difference with the substrate alloy in coefficient of linear expansion, the aluminum oxide coatings on the alloy surface easy to burst or to fall off in the circulation heating up and cooling down condition, so the coatings have to be manufactured into NixAly, FexAly intermetallic compounds or the MCrAlY alloy to form self-repair Al2O3gradient coatings in the use and enabled the substrate to have the good high temperature corrosion preventing.Now high temperature protective covering prepared in the domestic and foreign divides into two kinds primarily, infiltration Al-based diffusion coating and overlay coating in all kinds of spray coating and physical, chemistry vapor deposition primarily. There are also the coating modified in surface structure, ceramic coating, composite coating and smart coatings and so on.The proliferation coating needs simple process, inexpensive cost but the inevitable craft in preparation technology, because infiltrating Al is destruction for the matrix material in itself, so that this kind of substrate content of Co or Ni impervious alloy material, and not only the other non-impervious alloy material can infiltrate in short time but also it could be used long term in high temperature. Moreover, the infiltration the Al process will make the serious pollution to the environment. Relatively, all kinds of gable coatings prepared in spray methods is low quality request and small destruction for the matrix material, the coatings components are adjustable and the long-term use. Moreover it is difficult to coat big size and the anomalous shape work piece. Needs the expensive equipment investment, the craft cost is very high. So inexpensive cost, fine performance and widespread applying high temperature protective covering’s preparation method to research is a current domestic and foreign material research area important work.The galvanization method is the simple craft, little equipment invests and inexpensive production cost, and low quality, the shape request for matrix materials. This experiment combines the composite plating method and the thermal response proliferation technology to prepare nickel aluminum high temperature protective covering. Innovation of this topic on learning is composite plating technology applies to prepare the high temperature protective covering. Because the aluminum electrode potential loses to the hydrogen in the peroxide solution, the Al3+cannot galvanic deposit in the negative pole. In the non-water system may electricity aluminum-plating, but the cost is high, the craft is complex, flammable explosive, difficulty to form the scale production. Now domestic and foreign had the massive reports to the composite plating craft, and the electrochemistry technology also mature gradually. So it is hope to prepare the nickel aluminum high temperature protective covering in water based system. At present in the domestic and foreign literature reported the galvanization coating only limits applies in the normal temperature environment such as decoration and hard covering etc. Coatings cannot the chemical combination with the substrate and separated from the mataix under the high temperature. The nickel aluminum covering in the topic would make SHS process in heat treanment comdition, not only high melting point NixAly intermetallic compounds in coatings, but also motivate permeate reaction with the matrix to form FexAly transition layer into graded coatings.The experiment mainly includes four parts:The first part uses chemical plating to prepare aluminite powders packaged by nickel as the dispersing agent in the next compound plates, and it is the foundation of the corrosion resistance of alumina finally. The second part, compound plates aluminite powders packaged by nickel on to the plain steel through adjusting test parameter to an ideal end. The third part, the unreliable coatings on the plain steel and the substrate inter diffusion and osmosis through the heat treatment to form the corrosion resistance, wear resistant, the thermostable oxidized gradient coating with intermetallic compound. The fourth part test the protective covering corrosiveness through the electrochemistry experiment, and compare environment corrosiveness with the plain steel no coatings with coatings and without coatings.