Ceramic-composite coating consisted of Yttria Stabilized Zirconia (YSZ), Fe2O3 and aluminum powder has been successfully formed on Inconel 625 substrate by electrophoretic deposition (EPD). The coating density depends not only on the stability of the EPD suspension but also on the applied voltage. In the present study, a single stage voltage treatment at 60V and a two-stage voltage treatment at 30V followed by 60V of the EPD were used. A fresh green body of ceramic coating was dried at room temperature for 24 hours prior to heat-treated at temperature of 1200 °C for 4 hours with heating rate of 2°C/min using horizontal heated furnace under argon gas inert. The effect of single- and two-stage treatments on the microstructural and mechanical hardness of the coating were investigated by Field Emission-Scanning Electron Microscopy and Vickers hardness test, respectively. The elemental composition of the coating was analysed by Energy Dispersive Spectroscopy and the crystalline phases were identified by x-ray diffractometer. The results showed that a less porous structure, and therefore, higher hardness was observed on the coating formed by a two-stage voltage than that of resulting from a single-stage voltage. The crystalline phase formed on the coatings was dominated by a tetragonal phase of ZrO2.

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The effect of solution treatment on the microstructure and corrosion behavior of cast Mg-9Al-1Zn (AZ91) were studied by using electro-optical microscopy, X-ray diffraction (XRD) technique, and weight loss method. The solution treatment was done at 415°C for 2 h followed by a water quench. The as-cast AZ91 alloy composed of α-Mg phase and β-phase (Mg17Al12). Most of the β-phase was segregated along the grain boundaries. A significant reduction in the volume fraction of β-phase was obtained as a result of solution treatment. The β-phase precipitate was distributed randomly both at grain boundaries and in the grain interior as discrete particles of a few µm sizes. The solution treatment induced grain growth resulting in a significantly larger equiaxed grain in the range 100-500 µm. A higher corrosion rate was obtained for the solution treated alloy than the untreated one. The β-phase precipitate played a dual role in the corrosion of AZ91 alloy depending on its volume fraction in the alloy. A nearly continuous distribution of β-phase along grain boundaries in the as-cast alloy served as a barrier for corrosion across grain while the distribution of discrete particles in the solution-treated alloy accelerated corrosion in the surrounding matrix.

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