Investigation of structure and heat treatment of various grades of corrosion-resistant alloy VDM® alloy C-4

The phase stability of nickel-based solid solution VDM® Alloy C-4 was studied, and time-temperature-precipitation diagram was built. The processes of heat treatment of sheets and tubes made of VDM® Alloy C-4 were investigated. The following regime of heat treatment was chosen – annealing at 1100 °C for 10 min/mm thickness with further rapid cooling in air. It was also shown that the cooling rate should be higher than 0.1 °С/s to prevent sigma-phase formation along the grain boundaries.