Showing papers by "Ghulam Ishaq Khan Institute of Engineering Sciences and Technology published in 2002"

Precipitation and compositional changes in the structural phases of microalloyed automotive steels

Abstract: A wide range of low and medium carbon steels are now employed for the manufacturing of various kinds of automobile parts. The steels exhibit considerable production and cost benefits as compared with conventional steels. In this work, the interphase precipitation of V(C,N) particles has been observed in the pro-eutectoid ferrite and ferritic lamellae of pearlite of the microstructure that is crucial for strengthening of medium carbon microalloyed steels. The compositional changes in the microstructure and various kinds of precipitation that are normally observed in microalloyed steels have been examined using transmission electron microscopic and parallel energy loss spectroscopic (TEM-PEELS) analysis techniques. Random and non-random dispersion of V(C,N) were observed in both the grain boundary and lamellar ferrite regions. PEELS analysis identified relatively higher concentration of nitrogen in fine non-randomly dispersed particles formed during austenite decomposition by an interphase precipitation mechanism, as compared with coarser particles randomly distributed on dislocations within the pro-eutectoid ferrite. The results are consistent with the sequence and respective growth mechanisms of the precipitates.

Microstructural study on oxidation of aluminized coating on inconel 625

Abstract: The high-temperature oxidation behavior of aluminized Inconel 625 has been examined using scanning electron microscopy (SEM) and fine-probe spot and linescan energy dispersive spectroscopy (EDS) microanalysis techniques. The formation of adherent slowly growing metallic coatings is essential for protection against severe environments. The coated (aluminized) and uncoated samples were subsequently oxidized in air at 1000 and 1100 °C to examine the performance of the aluminized coating. The micro-structural changes that occurred in both coated and uncoated samples were examined. It was found that coated samples showed superior performance against high-temperature oxidation, as compared to the uncoated samples. The coated samples revealed uniform and adherent oxidized layer, as compared to the uncoated samples. The oxidation behavior and multilayered microstructural morphology observed in the coated samples can be attributed to the interdiffusion and variation in kinetics of oxidation.

Characterization of in-situ carbide coating of tungsten alloy

Abstract: Tungsten alloys, produced by liquid phase sintering and subsequent swaging, are used commonly for engineering and defense applications. In this investigation the morphology of carburized coating on a series of specimens of tungsten alloy has been examined using electron metallographic and microanalytical techniques. The samples were pack carburized at 850 °C for 30 and 60 min to determine the surface properties. The role of compositional changes, formation of tungsten and iron carbides and the interfacial structure of the carburized samples were examined. It is found that the surface properties of the tungsten alloy have been improved by the formation of these carbides in the carburized specimens as compared with the as-received specimen.

Potential of use of ion implantation as a means of catalyst manufacturing

Abstract: The objective of this paper is to demonstrate the applicability of an ion implantation technique for catalyst manufacturing. The increasing production of vehicle catalysts has resulted in a growing consumption of the noble metals. Traditional methods of coating, such as impregnation, are thought to reduce the porosity and specific surface area of the catalysts. When ion implantation is used, the ions of the catalytic material are implanted into the substrate surface without affecting these properties. Several catalysts on different substrates were prepared by ion implantation and tested. The platinum-implanted catalyst showed a carbon monoxide (CO) conversion efficiency equal to that of the impregnated catalyst but with a 15 times lower platinum content. The CO conversion efficiency of the base metal based catalyst is doubled by platinum implantation. Details of the ion implantation parameters and test results are provided.