Influence of solution treatment on microstructure, corrosion resistance, and oxidation behavior of cast G-NiCr28W alloy

Abstract

G-NiCr28W is a nickel-based cast alloy. Its microstructure consists of nickel-rich matrix phase and chromium-rich eutectic carbides. The solution treatment process can provide homogenous microstructure and desired mechanical/thermal properties for G-NiCr28W alloy. However, the solution treatment process affects the corrosion resistance of the alloy and it causes metal loss due to the occurrence of oxidation at atmospheric conditions. Therefore, determining the changes in the properties of the G-NiCr28W is important. For this purpose, G-NiCr28W specimens were solution treated at 1,040 ˚C, 1,100 ˚C and 1,160 ˚C for 1 h and 8 h, respectively. The microstructures of the solution-treated samples were characterized by optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction analysis. Moreover, hardness, corrosion resistance and oxidation behaviors of the solution-treated samples were examined. The solution treatment process applied at 1,160 ˚C led to the formation of Fe2W2C blocky carbides, and hardness of the sample increased with the existence of blocky carbides, while corrosion resistance decreased. Furthermore, excessive metal loss occurred depending on oxidation due to the high process temperature at 1,160 ˚C.