Sharif Digital Repository

During this research, ceramic coatings on titanium substrate were prepared by plasma electrolytic oxidation process at a constant current density. Effect of different parameters such as frequency, current density, additives and time on the characteristics of the coated samples was studied. Composition, structure and elemental distribution of the coatings were studied by XRD, SEM and wave-length dispersive spectroscopy (WDS), respectively. Various tests were carried out to calculate the amount of coatings porosity. Pin-On-Disk method was used to evaluate erosion resistance of coatings. Corrosion and erosion-corrosion behaviors of the coatings were studied in 3.5wt% sodium chloride aqueous... 

Plasma electrolytic oxidation (PEO) is currently recognized as an effective coating method on active metals such as magnesium. In this method, through occurrence of strong electric discharges on the surface of the anode accompanied by electrochemical and thermo-chemical reactions at plasma environment, a relatively thick ceramic coating with complex compounds grows on the metal surface which significantly improves its properties. Regarding the influence of PEO electrical parameters on the morphology and other properties of the coating, the objective of the present study is to prepare a quality ceramic coating on AZ31 magnesium alloy substrate via setting the process parameters, such as... 

The quest for increasing the efficiency of internal combustion engines is going on since the invention of automobile in the world. Wear between cylinder and ring is one of the major parameters reducing the engine performance. So many parameters are affecting the wear losses. Temperature plays a key role on the severity of wear condition in internal combustion engines. In conventional cast iron cylinders, we are not able to increase the temperature from a defined level; one reason is that the wear rate on cylinder ring contact will increase excessively. One of the major benefits of using ceramic coating is their ability to withstand in higher temperatures, while having adequate hardness to... 

Plasma electrolytic oxidation process (PEO) is now recognized as a relatively new method in surface engineering. In this process, formation of micro arcs resulted from electric discharges on the surface of the specimen in the appropriate electrolyte, is used to ionize the gas layer which has enshrouded the specimen. In the present study, ceramic coating on aluminized steel was produced by PEO process and the effects of the influential parameters were comprehensively investigated. For this purpose, coating on the aluminized steel with dimension of 25×30 mm² was produced under different condition of processing time from 1 to 15 minutes, current density from 10 to 20 A/dm², frequency from 50 to... 

Plasma Electrolytic Oxidation (PEO) method was used for the preparation of ceramic coatings on Aluminum 5052 substrate in a silicate-based electrolyte containing different concentrations of ZrO2 nanoparticles. Before the addition of nanoparticles into the electrolyte, determining process parameters including current density, coating time, and frequency were examined carefully. After studying corrosion behavior, thickness, and coating morphology in different circumstances, the frequency of 50Hz, the current density of 150mA/cm2, and the coating time of 20 minutes were chosen as the optimum parameters. After that and with the usage of those parameters, ZrO2 nanoparticles were added to the... 

In this study, biocompatible ceramic coating, containing hydroxyapatite particles (HA), was successfully created by AC anodizing, on the surface of commercially pure titanium grades 2. Coating process basically consisted of three methods. In Method 1, samples were anodized in a salty electrolyte containing calcium – phosphate base and in method 2 samples were anodized as initial process, following cathodic polarisation deposition of HA particles. Finally in method 3, samples were anodized in an electrolyte containing of HA particles suspension.Parameters such as current density and time of anodizing process, in first procedure, and time of cathodic deposition process in second procedure, and... 

This research focuses on finding an appropriate method for increasing wear and corrosion resistance of hard coating TiN PVD and chromium. The substrate was made up of 42CrMo4 (DIN) steel (used for marine industries) and coated by TiN Arc PVD process and hard chromium electro-deposition. The results of these two coatings are compared and the better coating which is TiN Arc PVD is suggested. To find the best method for coating, several test studies are organized such as: the mechanical and tribological properties of TiN PVD and hard chromium coatings for wear and corrosion resistance applications are organized. The potentiodynamic polarization technique was used to measure the corrosion rate... 

Considering the importance of biocompatibility of implantable prothesis’, metallic alloys have weaker corrosion resistance than ceramics. In order to extend usage of nanomaterials to improve the bio-properties of materials, Nano-structured ceramic coatings are being suggested to improve corrosion resistance and biocompatibility of prosthesis. Meanwhile, very good properties of TiN, such as corrosion resistance and mechanical properties as a thin film coating are undeniable. In this study, TiN and Ti2N thin film were deposited on Ti-based substrate, using PVD and Magnetron sputtering at different argon to nitrogen ratio. The crystal structure of the films was examined using Grazing XRD...