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Abstract:The present study emphasizes on joints two industrially important materials AISI 304 with AISI 1021steels, produced by friction welding have been investigated. Samples were welded under different axial pressures ranging from 75MPa to 135MPa, at constant speed of 920rpm. The tensile strength, torsional strength, impact strength and micro hardness values of the weldments were determined and evaluated. Simultaneously the fractrography of the tensile tested specimens were carried out, so as to understand the failure analysis. It was observed that improved mechanical properties were noticed at higher axial pressures. Ductile failures of weldments were also observed at 120MPa and 135MPa axial pressures during fractography analysis.

Friction welding is widely used as a mass production method in various industries. In the present study, an experimental setup was designed in order to achieve friction welding of plastically deformed AISI 1021 steels. In this study, low alloy steel (AISI 1021) was welded under different welding parameters and afterwards the mechanical properties such as tensile strength, impact strength and hardness were experimentally determined. On the basis of the results obtained from the experimentation, the graphs were plotted. It is the strength of welded joints, which is fundamental property to the service reliability of the weldments and hence present work was undertaken to study the influence of axial pressure and rotational speed in friction welded joints. Axial pressure and rotational speed are the two major parameters which can influence the strength and hence the mechanical properties of the friction welded joints. Thus the axial pressure and rotational speed were taken as welding parameters, which reflect the mechanical properties.

High-temperature corrosion of coal-fired boiler parts such as water walls and superheated tubes poses a serious threat to the efficiency of the thermal power plant. To overcome this, numbers of corrosion control techniques are commonly employed. But, a dense and defectfree coating deposited by the thermal spray technique has shown promising result to combat hot corrosion. Although open or closed porosity in distinct thermal spray coatings can originate from distinct factors such as partial or totally un-molten particles, inadequate flow or fragmentation of the molten particle at impact, non-optimal spray angle and entrapped gas. But, this can still only be prevented by coating post-treatment. Hence, in this paper, authors have reviewed the performance of distinct coatings deposited by diverse thermal spray processes. Then, the effect of distinct process parameters and heat treatments on microstructure and mechanical properties of coatings is described. Finally, the best coatings are suggested to combat maximum hot corrosion of boiler tubes.

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