Preparation and characterization of a sodium polyacrylate/sodium silicate binder used in oxidation resistant coating for titanium alloy at high temperature

A sodium polyacrylate/sodium silicate binder used in oxidation resistant coating was investigated, and its effect on oxidation behavior of titanium alloy was studied at 800 °C in air. Glass-ceramic coating slurry mixed with the binder had good dispersity and stability. The coating was deposited on Ti-6Al-4V titanium alloy through the slurry-dipping method. Better oxidation resistance was obtained at an elevated temperature, and the thickness of the α-case layer was reduced by 71%. The microstructure of the binder consisted of spherical molecules, large molecules, and a stick organization. The phase was composed of several crystalline phases and an amorphous phase. At a temperature range of 100 °C to 1200 °C, the total weight loss was 28.3%. A stable state could be obtained at above 700 °C, which ensured a perfect barrier for protecting the alloy from oxidation. During cooling, the coating can be peeled off easily because of the mismatched coefficient of thermal expansion between the glass and substrate, and the carbon oxidation of the binder.

A new binder of sodium polyacrylate/sodium silicate (PAAS/Na2SiO3) was obtained. Experimental results showed that the oxidation resistance of the coating mixed with a new binder in (b) was as good as the one with Na2SiO3 binder in (a). In addition, the coating with the new binder can be peeled off much easily during cooling.Figure optionsDownload as PowerPoint slideHighlights
► A new organic–inorganic binder used in oxidation resistant coating was studied.
► The new binder was a mixture of sodium polyacrylate and sodium silicate.
► The microstructure and phase of the new binder were described systematically.
► The oxidation resistance effect of the obtained coating was investigated.