Journal of Advanced Processes in Materials Engineering
Year:2010 | Volume:4 | Issue:2 (13)|Papers Count:8

The aim of this work was preparation, development and characterization of nanostructure bioactive glass (NBG)-titania coating by sol-gel technique for improvement of biocompatibility of 316L stainless steel implant used in dentistry and orthopaedic surgery. Nano bioglass 58S have been prepared by quick sol-gel method and after calcination at 600oC was added to titania sol in concentrations 30, 50 and 70 grams/liter. Composite sols were coated on stainless steel 316L using dip-coating method and heat treated at 600oC. The physicochemical properties, including surface morphology, crystallinity, crystal size and adhesion on steel substrate, of the films were investigated by SEM, EDS, XRD, TEM and micro hardness test method. Macro crack-free and homogeneous bioglass-TiO2 composite coatings were obtained, particle size less than 100 nm and an excellent adhesion between the films and the stainless steel substrate (450 vickers). The bioactivity of bioglass-TiO2 composite coatings was investigated by immersing the coatings in simulated body fluid (SBF) for 30 days. After 30 days immersion, a layer of carbonate-containing apatite was formed on the coatings surface. With increasing bioglass concentration the hydroxyl apatite content was increased.

In this paper, corrosion behavior among individual parts of a 17-4 PH repair welded in 3.5% NaCl by various DC electrochemical measurements were studied. Also, the influence of three Post Weld Heat Treatment (PWHT), solution annealing followed by aging at 480, 550 and 620oC on corrosion resistance was investigated. Potentiodynamic polarization measurement in as-weld specimen revealed a lower passive current density and a higher pitting potential in the weld region, while the HAZ showed the highest passive current density and the lowest pitting potential. Galvanic coupling also showed that the weld metal/HAZ couple with the HAZ acting as the anode and weld metal as the cathode has the highest risk of galvanic corrosion among the three individual galvanic couples. By applying PWHT’s HAZ was disappeared and improve the passivity of weld region by increasing the pitting potential. Galvanic corrosion measurement showed that PWHT’s improve the galvanic corrosion resistance.

In this paper, the crystallization behavior of fluorphlogopite, a glass-ceramic in the system MgO-SiO2-Al2O3-K2O-B2O3-TiO2-F was studied by substitution of Li2O for K2O in the glass composition. DTA, XRD and SEM were used for the study of crystallization behavior and microstructure of the resulting glass-ceramics. Development of crystalline phases on thermal treatments of the glass at various temperatures has been analyzed by X-ray diffraction. Microstructure of the crystalline phases was investigated by scanning electron microscopy (SEM) and the development of structural features with variation in heat treatment temperature was observed. The results showed that with increasing of lithia content, glass transition temperature (Tg) and crystallization temperature (Tp) decrease. In the potassium-containing compositions, pottasium-mica and potassium silicate phases were crystallized. b-spodumene and chondrodite phases were observed in the lithia containing compositions.

Lost foam casting has been used as a production method since 1950. This process has the capability to put different types of fiber and particles inside the polystyrene pattern before starting to cast. The process utilized in this research can be also regarded as a promising approach for production composite and bimetals. Furthermore, this process can be used for studying interface reactions between a given melt and supposed solid insert. In this research, Aluminum wire with a diameter of 3 mm inserted in polystyrene pattern and then gray cast iron was poured. States of melting Aluminum insert, different Fe/Al intermetallic phases and effect of Aluminum on the graphite in interface were studied by Scanning Electron Microscopy. Results showed that formation of different intermetallic components such as FeAl3, FeAl2, FeAl and Fe3AlCx at Fe/Al/C interface.

In this investigation, different coatings on CK45 steel surface was applied by Electro spark method. Using two kinds of electrode including hard facing chromium-steel electrode and Ni-TiC composite electrode, microstructure and tribological properties were investigated. The scanning electron microscopy (SEM) was used to characterize the product. Tribological properties of the coatings were studied by wear test. SEM photographs show that uncoated sample has a lamination wear mechanism unlike of coated samples with scratch wear mechanism. Composite coating has a lower wear than chromium-steel coating because of uniform distributed TiC particles in the nickel matrix as reinforcement. Results of the wear tests indicated that the uncoated sample has friction value about 0.31 whereas composite coated sample had 0.165 friction value. Uncoated sample experience shear, tensile and compressive stresses which may lead to failure by cracking and spalling. Wear mechanism changes by coating application from delamination to scratching and cause to lower abrasion.

The growing interest in studies on ultrafine - grained metallic materials is motivated by attractive mechanical properties, such as high strength with sufficient ductility. In recent years, severe plastic deformation (SPD) techniques have gained importance because of production of ultrafine grain materials with outstanding new properties. Multi - directional forging (MDF) is one of SPD methods that assume the advantage of MDF in its high efficiency and low processing cost. In this paper the influence of annealing time regarding the microstructure and microhardness of ultrafine - grained low carbon steel produced by multi - directional forging was studied. Results show that with increasing time grain grows take place and microhardness decreases.

This work deals with the preparation of Aluminium-substituted Nickel ferrite by powder metallurgy method in different Al contents (X=0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 in NiAlxFe2-xO4). Magnetic properties of samples are measured by an LCR meter; morphology and structure of samples are characterized by SEM and XRD, respectively. The effect of Al content and grain size on effective magnetic permeability (meff), equivalent series resistance (RESR), Curie temperature (Tc) and lattice parameter have been investigated. The results show that the above parameters decrease as Al content increases.

In this paper, in order to increase the capability of controlling properties and chemical composition in production of Cu-20Zn brass alloy, the optimal fabrication condition of this alloy via powder metallurgy method (PM) was investigated. For this purpose, prealloyed brass powder made by water atomization process, with average particle size of 40 to 100 mm, was compacted under 600 MPa pressure and sintered at the temperature range of 800 to 1000oC in Ar atmosphere. The results of the density measurement, hardness and impact energy testing show that the optimum sintering temperature is 930oC. Properties’ improvement through sintering at optimum temperature was occurred as a result of high connectivity between particles and the decrease in the number of pores due to liquid phase sintering process.