Modeling High-Alloy Chromium-Nickel Alloy Nanostructuring with Treatment by Highly-Concentrated Energy Sources

Resumo

A mathematical model is provided for phase transformation thermodynamics making comprehensive study possible for the equilibrium phase composition of chromium-nickel welded joints at different temperatures. According to the model, with a chromium content of more than 22 wt.% the temperature for the start of intermetallic precipitation exceeds the solidus temperature for Cr–Ni alloy, i.e., in this case precipitation of primary Ni₃Al intermetallic is thermodynamically possible. Primary Ni₃Ti precipitates are probable with a chromium content of more than 36 wt.%. Model calculations are confirmed by microstructural studies. In order to improve welded joint strength for the alloy in question, slow joint cooling in the range below 1000°C is recommended, depending on welded structure operating temperature, and ageing in the range of intense γ′-phase precipitation, i.e., 900–600°C. The mathematical model developed for phase transformation thermodynamics may be used for studying the phase composition of other chromium-nickel alloys.