Processing and electrochemical characterization of Ni2Si intermetallic compound produced by vacuum sintering

In this study, a powder metallurgy approach for fabrication of Ni2Si intermetallic compound was utilized. In this regard, mechanically activated Ni-33 at.% Si powders were used as feedstock. The powders were investigated by differential scanning calorimetry to study phase transformations that occurred during heating in the calorimeter. It was shown that the milled powders reacted after heating up to 850 °C. In order to fabricate bulk Ni-33 at.% Si, the as-milled powders were cold-pressed and subsequently sintered at 900 °C for 1 h in a vacuum furnace. X-ray diffraction results indicated that the phase composition of sintered materials consisted of only δ-Ni2Si intermetallic. Consolidated samples exhibit 12% porosity and microhardness up to 773 HV0.05. Further investigations showed the corrosion rate of sintered compound is higher than that of Ni–Si alloys reported in the literature. Here, anodic dissolution near the surface pores seems to be corrosion mechanism which resulted in increase in surface porosity up to 27% after corrosion.

► δ-Ni2Si was fabricated through mechanical activation and reactive sintering.
► Sintered samples exhibited high microhardness values up to 773 HV.
► EIS measurements showed the corrosion is under the charge transfer control.
► Anodic dissolution near the pores seems to be the corrosion mechanism.