Dissolution Behavior of Eutectic Carbides in Medium-Alloy Steels for Heavy Forgings

Area of Science:

• Metallurgical Engineering
• Materials Science
• Physical Metallurgy

Background:

• Eutectic carbides significantly influence the mechanical properties of heavy forgings.
• Understanding carbide dissolution is crucial for optimizing steel performance.

Purpose of the Study:

• To investigate the dissolution behavior of eutectic carbides in MoVW2 and MoV steels.
• To analyze the impact of dissolution on microstructure and hardness.
• To explore the role of alloying elements and solidification on carbide formation.

Main Methods:

• High-temperature diffusion treatment at 1230 °C for up to 100 hours.
• Microstructural analysis using Scanning Electron Microscopy with Electron Backscatter Diffraction (SEM+EBSD).
• Image analysis with ImageJ and thermodynamic calculations using Thermo-Calc.

Main Results:

• Coarse eutectic carbides gradually dissolved, becoming more uniform and spherical.
• Steel hardness significantly increased after 50 hours of holding, attributed to solid solution strengthening.
• Higher tungsten (W) content in MoVW2 steel promoted M₆C carbide precipitation.
• M₇C₃ carbides precipitated in both steels during late-stage solidification due to carbon (C) and chromium (Cr) enrichment.

Conclusions:

• Eutectic carbide dissolution refines microstructure and enhances hardness in MoVW2 and MoV steels.
• Tungsten and solidification conditions play key roles in carbide precipitation and stability.
• The findings provide insights for tailoring heat treatments to improve heavy forging properties.