ПІДВИЩЕННЯ КОРОЗІЙНОЇ СТІЙКОСТІ ПЛАЗМОВИХ ПОКРИТТІВ НА ОСНОВІ ПЛАКОВАНОГО ПОРОШКУ ОКСИДУ АЛЮМІНІЮ

Анотація

Експериментально досліджено корозійну стійкість покриттів, отриманих плазмовим напилюванням порошку оксиду алюмінію плакованого двошаровими оболонками з титану, алюмінію або міді на сталеву та магнієву основу. Проведена термодинамічна оцінка взаємодії оксиду алюмінію з металевими оболонками при плакуванні. Встановлено вплив плакованих порошків на мікроструктуру та пористість плазмових покриттів і зміну поляризаційного опору під час випробувань в рідких агресивних середовищах.


Corrosion resistance coatings deposited by plasma spraying of alumina powders with clad metal PVD film were studied. Thermodynamical evaluation of the interaction of alumina with titanium and copper in cladding was produced. Possibility of interaction was evaluated assuming that the alumina dissolved in the titanium. The result was defined atomic percentage of oxygen and aluminum in the titanium at temperature of cladding. The influence of clad powders on the microstructure, porosity and polarization resistance of plasma-sprayed coatings during testing in corrosive environments was studied. The corrosion behavior of coating was studied by technique of a polarization change based on the measurement of the current between the two electrodes from the same metal and a coating when applied the polarization less than 20 mV.

Alumina powder for plasma spraying coated dual layer of titanium, aluminum or copper reduces the total porosity and improves in a 2–3 times the corrosion resistance of coated steel in 10 % solution H2SO4, HNO3 as well as more than an order of corrosion resistance of magnesium alloy in a 3 % NaCl solution.

Largest values at spraying on steel substrate of the polarization resistance in acid solutions respond coatings from alumina powder with dual layer clad PVD film of titanium and copper. This increase in the corrosion resistance depends more on the thickness of the top sprayed coating than to the material and thickness of sprayed underlayer. It is associated with a decrease in the amount connected pores. Largest values at spraying on the magnesium alloy of the polarization resistance in 3 % NaCl solution had coating on base of clad alumina powder with underlayer and the additional activation of the substrate surface by electrospark doping for improving adhesion strength.

Further research perspectives are to enhance materials for clad powders and more detailed studying of the corrosion damage mechanism at elevated temperatures of plasma-sprayed coatings from clad powders.


СМИРНОВ І. В., д.т.н., доц.


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