Journal of Advanced Processes in Materials Engineering
Year:2010 | Volume:3 | Issue:4 (11)|Papers Count:8

Alumina-Spinel castables are widely used and replaced instead of traditional refractory bricks for many industrial application. That is because of the best resistance to slag penetration and other properties. This study aims to make Alumina-Spinel castables and evaluate the effects of grain size distributions and Spinel on the properties. Aggregates used were tabular alumina while fine and ultra fine aluminas were of calcined type. the alumina cement cotained 17 wt % CaO and synthetic spinel (MAS 76) microsilica, dead burnt magnesia (M99) and additives were used. After making the samples, the properties such as flowability, CMOR, CCS, bulk density, were measured. Microstructural and phase analysis were conducted by SEM and XRD. The data showed that flow value of castables slightly was increased with fine addition. The grain size distributions and shape of grains influence on rheological behavior and flowability of castables. Addition of fine particles into the composition decreased the interference between coarse particles. Fine particles decreased the viscosity of castable matrix therefore flow ability increased. The results showed that the strength decreases by increasing fine grain size due to increasing requaird water. Cold crushing strength after firing at 1500oC for 3h increases with increas in spinel content. XRD diffraction and SEM of the microstructure of castable reveals the growth of CA6 crystals out of the Al2O3-rich spinel grains in the bonding matrix of the castable. Cao react with Al2O3 in the Al2O3-rich spinel for the formation of CA6 to set up the bond linkage between CA6 and spinel grains in the bonding matrix.

In the electroplating process can be well used by Add-on complex instrument; the percentage of alloy elements in the alloy coating can be controlled. While this is to create of composite coatings with neutral particles cannot easily type and percentage of sedimentary particles can be controlled. In this study, to control percent neutral particles in composite coatings of the property and zeta potential factors that have been used. Obtained coverage of metallurgical structure and chemical composition with a microscope SEM, EDX and XRD were analyzed. The results showed that increase of pH of solution caused decrease of zeta potential. Therefore, both pH and current density are effective parameters on particles content of nanocomposite coatings. By studying the effect of the zeta potential and the factors affecting it, it can be concluded that by specifying the optimal conditions from the view of the weight percentage of the neutral elements inside the coating and electroplating conditions, there is the possibility of the production of a nanocomposite coating with high quality and no additives.

In this investigation effect of shakout time on microstructure and mechanical properties of pearlite ductile cast iron with minimum alloying element and without Isothermal Heat Treatment had been studied. For these reason standard Y- block that designed with in-mold process used and fabricated with different chemical analysis, for control the cooling curve used the S-thermocouple (Pt-Rh) in the mold, after casting with control of cooling curve, the Y-block shakout from molds and then cooled in the air. Then standard specimens machined for mechanical and metallographic examination. The metallographic exam result showed that with increased the rate of shakout time, the pearlite in microstructure increased, also the mechanical exam result showed that with increased the rate of shakout time, hardness and tensile strength increased elongation and impact energy decreased.

Austempered ductile irons (ADI) have attractive properties such as high strength, ductility, toughness and good wear resistance, therefore have special situation in transport industry, and substitute to steel parts. These properties can be achieved upon adequate chemical composition and heat treatment which yields optimum microstructure and mechanical properties. The most problem in application of these materials is low machinability which increasing cost of machining products. In this paper an investigation has been conducted on ADI's with different chemical compositions and heat treatments. The microstructure developed throughout these treatments has been identified by means of metallography microscopy. The abrasion of machining tool is a criteria for comparing of machinability of specimens. Based on these results an optimal processing window has been established for production ADI's.

Two stellite layers were produced as protective coatings by a 1.5 Kw CO2 continous wave laser remelting of the stellite 6 powders on plates of AISI 420 martensitic stainless steel in Ar environment and investigated experimentally. Scanning electron microscopic microphotographs and EDS analysis reveal a strong metallurgical bond between the substrate and coating as well as the structural homogeneity along the depth of the layers which is characterized by a chemical composition close to that of the powder. The laser clad layers show a dendritic and fine grained structure with a minor presence of impurities. For the coatings an improvement of mechanical properties such as the wear resistance and microhardness values compared to those of substrate is observed. Also it is obtained that corrosion resistance is increased so much.

The material has been studied in this research is DIN 18CrNi8 steel that has been subjected to pack carburizing process. After carburizing followed quenching, surface hardness of this steel increases according to formation of marten site structure in outer layer of steel. The core region of steel has more flexibility and less hardness because its carbon content is lower than the surface. Study of harden ability is one of the important parameters in hardening treatment of these steels. In this research steel specimens were subjected to graphite powder. Then, they were heat treated at 925oC for about 3, 5, 8 and 12 hours respectively. Finally these parts were quenched in oil. Filling of carburizing pack was done by three methods: pack with air gap, pack without air gap and pack with activator material. Sodium carbonate was used as an activator material. For determining of carburizing depth, micro hardness test was done on cross section of specimens. Plotting the case depth versus carburizing time determined necessary time needed to achieve specified case depth in various pack filling conditions. Case depth increases in all conditions with increasing the carburizing time, Except in pack within air gap that case depth increases with carburizing time increasing by a specific time, but in more carburizing times, decarburization phenomenon happenes and then case depth decreases. Also, comparison between no complete filling of carburizing pack and adding the activator material on hardenability of carburized steels was investigated.

This study was carried out to determine the effect of heat treatment on Characteristic of HARDOX 600. In this study the samples was heat treated in different temperature for 5 hours and then quenched in medium atmosphere. Microstructure and hardness of samples were studied by optical microscopy, X-ray diffraction (XRD) and hardness test. The results show that heat treatment of plate causes changing in microstructure, structure and hardness. Increasing heat treatment temperature causes increasing changing in microstructure and hardness due to tempering of samples. Also the maximum changing was seen in 500oC heat treatment temperature resulting in decreasing wear resistance of plate.

In order to extract rhenium from roasted molybdenite, rhenium and molybdenium ions were optained by dissolving the rare materials, separation and various concentration methods and finaly crystalizations of rhenium salts. Dissolving process was started with rhenium extraction. It can be use acidic, basic or present of antioxide materials for dissolving. In this study dissolving of flue dust Roasting of molybdenite was proceed with nitrid acid, sodium Hypochlorid, Hydrogen peroxide, oxygen, sodium Hydroxide and calcium Hydroxide and best composition of solvent with suitable concentrations, highest dissolving of rhenium, were selected.