STUDY ON WELD ABILITY OF 50/50 Ni/Cr ALLOY

Abstract

In the present study observing the metallurgical transformations due to the high service temperature, and the effect of this transformation on mechanical properties and weld ability of the alloy of interest (as cast and after service). Various heat treatment regimes at different temperatures and welding at different heat inputs, several facts about the phase structure evolution and its relation to the deterioration in mechanical properties. It is related to precipitation of Cr-rich a-phase inside y- phase at low service temperatures (close to 700°C).This precipitation gets slightly enhanced if the alloy is previously heated at higher temperatures (1050°C) due to the high solubility of Cr in the y-phase at these temperatures as compared with that at service temperatures (close to 700°C). Also heat input controls the hardness profile across the weld, with higher possibility of formation of local hard zone and hard throat as the cooling rate decreases, especially for the as-cast alloy. Hard throat could be avoided by either increasing or decreasing the heat input beyond a critical value.