EFFECT OF ARC CURRENT ON MICROSTRUCTURAL CHARACTERISTICS OF PLASMA TRANSFERRED ARC HARDFACED NICKEL ALLOY
Keywords:Austenitic stainless steel, Plasma transferred arc hardfacing, Microstructure
In this investigation, plasma transferred arc (PTA) hardfacing was done on AISI 316 LN austenitic stainless steel (ASS) plates using Nickel base alloy (Colmonoy 5 powder). ASS plate was preheated at 4000C to avoid cracking. After hardfacing the samples are immersed in the vermiculite powder to confirm the moderate cooling and avoiding crack. The arc current was varied between 120A to 150A and other parameters such as, traverse speed, powder feed rate, standoff distance, torch oscillation width were kept constant. From this investigation, it is found that the microstructure of the PTA hardfaced deposit overwhelmingly comprises of the γ-Ni phase and the interdendritic eutectic mixture comprised of γ-nickel and nickel-rich borides. These investigation also exposed the presence of chromium-rich carbides and borides in a γ-Nickel matrix. Ni-based deposits showed superior hardness compared to the substrate.
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