Papers by Author: Shahjahan Mridha

Abstract: The increasing need for energy efficient tribo-composite surfaces has led to the enhancement of surface properties of engineering components through parameter processing control. This study was carried out to investigate the hardness behaviour of low alloy steel (LAS) surface modified with TiC under a tungsten inert gas (TIG) arc torch. The effects of welding current, traversing speed, arc voltage and argon flow rate on surface hardness during the surface alloying treatment were analyzed using Taguchi’s experimental design. The hardness behaviour of the TIG-processed composite coating was assessed with a Wilson Wolpert microhardness machine. The analysis of the experimental results based on the Taguchi’s design revealed that the welding speed and welding voltage are the most significant process parameters influencing the surface hardness performance of the composite coated layer. The signal-to-noise response was used to identify the optimum parameter combination for maximizing the surface quality characteristics. The validity of this approach was confirmed based on the good agreement between the predicted value and experimental result obtained at the tested optimal conditions.

Abstract: The superalloy of Inconel 718 variety is widely used to produce compressor blade in gas turbine engine. The blade tip invariably wears in services and thus requires frequent metallization for repairing. In most commercial Turbine Engine Industries the metallised blades, after grinding, undergo a stress relieving heat treatment at 7600C before return for applications. In this study, the metallised blade is heat treated at different conditions and compared its microstructure and hardness with those of the standard stress relieving treatment blades used in most industries. The microstructure of the stress relieving sample contains dendrite with hardness of 230 HV for the melt zone, 190 HV for the Heat Affected Zone (HAZ) and 420 HV for the parent metal. Solutionising at 982 or 10660C developed hardness less than 220 HV in all sections. By long time ageing treatment of the solutionised sample developed high hardness across the whole blade. These treatments homogenized the microstructure and produced high hardness values by precipitation of secondary phase structures across the blade.