الفهرس 
Chapter One literature ReviewOnly 14 pages are availabe for public view
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Abstract
Superalloys exhibit outstanding mechanical strength, creep resistance and corrosion resistance at high temperature. They are used where the most severe environments are encountered in aircraft, power generation, and vehicular gas turbines. However, Nickel based superalloys lack adequate resistance to hot corrosion caused by deposits from fossil fuels. The aim of this work is to improve the hot corrosion and oxidation resistance of nickel base super alloy IN 617 by using pack cementation process .Three different types of pack cementation processes were applied. Namely,aluminizing, chromizing and chromolauminizing with the addtion of reactive CeO2. The heat treatment regime was heating at 670 °C for 2.5 hrs then raising temperature to 1050°C and holding for 5 hrs Aluminizing process produced layer with thickness 86 μm of β-NiAl phase, chromolauminizing process produced layer with thickness 145 μm of phases are Cr5Al8 precipitates and Ni2Al3 formed in NiAl matrix. Also some addition of reactive compound (CeO2) of the coating layer and produced phases of Al2O3, Cr2Ni3 and Ni3Al. The layer thickness was 76 μm. The cyclic oxidation tests for different layers formed and untreated substrates were conducted at 1000°Cfor240hr.Itwas observed that the chromoaluminized layer has excellent oxidation resistance due to dense and protective alumina layer formed on the surface. Hot corrosion testing on different layers formed and untreated base alloy were conducted at 900◦C in supersaturated solution of 10%NaCL+90%Na2SO4 for 240 hr. It was found that the chromoaluminized layer has excellent resistance to hot corrosion at 900 ◦C. The layers microstructure was investigated by optical microscope, scanning electron microscope (SEM).Hardness changes through the various layers were investigated by vicker s hardness tester. Composition ʼ of layers formed was also investigated using the energy dispersive X-ray analysis (EDAX) and phases formed were investigated using x-ray diffraction XRD.