Experimental investigation of phase equilibria in the Cr-Mo-Si ternary system at 1500 °C

Phase equilibria in a Si-lean region (x$_{Si}$ ≤ 25 at.%) of the Cr-Mo-Si ternary system at 1500 °C is experimentally investigated by means of scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). For the first time, the existence of a stable ternary compound (σ-phase) after the heat treatment at 1500 °C for 200 h is confirmed. The σ-phase is stable within 12.5-13.5 at.% of silicon, 30.6-48.3 at.% of molybdenum and 38.7-56.8 at. % of chromium. The partial isothermal section at 1500 °C refined in the vicinity of the σ-phase is constructed based on newly obtained experimental data. The examined section contains three single-phase regions ((Cr,Mo)3Si, σ-phase and a single-phase solid solution (Cr,Mo)ss), three two-phase regions ((Cr,Mo)ss + (Cr,Mo)$_3$Si, σ + (Cr,Mo)ss and σ + (Cr,Mo)$_3$Si), and one three-phase region (σ + (Cr,Mo)ss + (Cr,Mo)$_3$Si).