High Temperature Corrosion of Nickel Based Heat Resistant Alloys and their Diffusion Brazed Parts(Materials, Metallurgy & Weldability)

概要

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High temperature corrosion, hot corrsion, of nickel based alloys and their brazed parts was investigated using mixed ash composed of 90%Na_2SO_4+10%NaCl at 800-950℃. The corrosion resistance of nickel alloys were determined by the value of effective chromium. The highest resistance was obtained in the alloy 738LC with maximum effective chromium. The corrosion resistant 738LC alloy formed Cr_2O_3 on surface layer as a main products after corrosion, the others formed mainly nickel oxides. High temperature oxidation is controlled by the aluminum to titanium ratio, the oxidation resistance became higher with the ratio. The brazed parts showed almost equal hot corrosion resistance to base metal exhibiting homogeneous distribution of each element in base metal after brazing heat cycle adopted in the present work. The activation energies obtained by hot corrosion test were ranging from 234 to 264KJ/mol.
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