In-situ Surface Enhanced Raman Spectroscopy of Surface Film Formed on Nickel-based Alloys in High-temperature and High-pressure Water

In-situ surface enhanced raman spectroscopy (SERS) was used to investigate the surface films formed on Ni-based alloys.SERS spectra measured for oxides of Ni-5Cr-8Fe shows Raman peaks at 540 cm-1,610 cm-1,and 670 cm-1.The peak at 610 cm-1 indicates the presence of Cr2O3.540 cm-1 peak is attributed to Cr2O3 or NiO or the mixture of both.670 cm-1 peak is assigned to FeCr2O4 spinel.The surface film of Ni-10Cr-8Fe alloy consists of Cr2O3,FeCr2O4 spinel and possibly NiO.Cr2O3 film is formed on Ni-10Cr and Ni-20Cr,but no spinel oxide peak is observed in the SERS spectra.As the Cr concentration increases,the amount of Cr2O3 in the surface film increases but the amount of NiO decreases.