Pingyi Guo

Effect of LaCrO3 coating on high temperature oxidation of type 316 stainless steel

Abstract A dense and conductive LaCrO 3 coating was prepared on type 316 stainless steel (316 SS), aiming at exploring its potential applications in SOFC and in other high temperature environments. Powder of LaCrO 3 with perovskite structure was synthesized by sol-gel method. LaCrO 3 coating on 316 SS substrate was obtained by slurry coating technique. The microstructure of the coating on 316 SS after sintering in air at 800 and 900 °C for 200 h was characterized. The effect of LaCrO 3 coating on oxidation resistance of the steel in air was also investigated. The results showed that the coating was adhesive to the substrate and improved greatly the oxidation resistance of the alloy.

Characterization of high-temperature oxide films on dysprosium-doped Fe-20Cr alloys by electrochemical techniques

Abstract The oxidation properties of Fe-20Cr, Fe-20Cr-0.2Dy and Fe-20Cr-1Dy alloys were studied using gravimetric and electrochemical techniques. The high-temperature oxide films of Dy-doped Fe-20Cr alloys were prepared in air at 900 °C for 24, 48 and 100 h, respectively. The electrochemical experiment was performed by a three-electrode electrochemical cell and in 0.1 mol/L Na 2 SO 4 aqueous solution. Proper models were built for describing electrochemical impedance spectroscopy of the different oxide layers and the spectra were interpreted in terms of a two-layer model of the films. The results revealed that the oxide films of Dy-doped Fe-20Cr alloys became compacter than that of undoped alloys and retained their good protective ability for a relatively long time. With increasing content of Dy, the protection of the oxide films slightly decreased. Mott-Schottky curves indicated that all the oxides were n-type semi-conductors, and the N d value of oxide film on Fe-20Cr was much larger than that of Dy-doped Fe-20Cr alloys. The results of kinetic curves and SEM were in agreement with electrochemical impedance spectroscopy and Mott-Schottky data.

Effect of the Electrolytic Solution Composition on Properties of Ceramic Coatings on Ti Produced by PEO

Ceramic oxide coatings were produced on pure titanium by plasma electrolytic oxidation in different electrolytes. The variation of coating thickness with applied voltages revealed coating almost kept a steady-state growth rate in electrolyte A and B, but not for electrolyte C. Numerous nodules occurred on the surface of the coatings at 200V in electrolyte A and B, and then nodules disappeared with the applied voltage increasing to 300V. There was no nodules occurred, and pore size was evidently different in electrolyte C. When the applied voltage was 300V, the coating formed in electrolyte C exhibited the highest corrosion potential and lowest corrosion current density in 3.5% NaCl aqueous solution.

Analysis for Fracture Behavior of Compactor Grinding Tooth Forging Die Based on Finite Element Method

For forging die fracture behaviors during the actual forging process of compactor grinding tooth, the fully forging process has been simulated based on FEM. Die stress changes and distributions were analyzed in details through two related simulation processes. The maximum load acting on the die which type is ideal rigid body predicted firstly. Then, the die stress can be obtained by the elastic-plastic analysis when the die bears maximum load. Results show that Local stress concentration beyond ultimate strength of material causes the fracture of lower die.

Influence of Cross Section Shapes of Preformed Blade Body for Final Forging Formability Based on Numerical Simulation

During the preform design of blade body, the final forging process for blade body with different transverse cross section shapes coupled different twist angles along blade body are simulated by using DEFORM-2D finite element analysis software. The final forging quality effected by different perform structures of blade body are analyzed in details through comparing some key factors such as formability, deformation uniformity, loss of heat before deformation. The valuable references are obtained for further design of optimizing blade body shape.

Growth Mechanism and Corrosion Behavior of Ceramic Coatings on CP-Ti Produced by Plasma Electrolytic Oxidation

Ceramic coatings were prepared in situ on commercial pure Ti(CP-Ti) by Plasma Electrolytic Oxidation(PEO) technology in an environmental-friendly solution. The voltage–time responses were recorded during different PEO processes. For short treatment times, the formation processes of ceramic coatings follow a linear kinetics, while for longer times the kinetics departs from the linear behavior. The surficial morphology and composition of the coatings was studies by X-ray diffraction(XRD) and scanning electron microscopy (SEM). The acted electrochemical method was used to evaluate the corrosion of the coated samples in 1moll-1 NaOH solution. The potentiodynamic polarization curves of coated titanium samples and the untreated metal substrate show that the PEO coated titanium samples possess much higher corrosion potential and lower corrosion current than uncoated aluminum alloy. It is noticed that the passive current density of the samples decreased from 10-4A/cm2, for the titanium, to 10-7 A/cm2, for PEO coated titanium sample.