Nanocrystalline Stainless Steel Electrodeposition
We report here the successful preparation of nanocrystalline FeCrNi electrodeposits by employing a double-compartment electrochemical cell where the anode electrode is separated from the cathode electrode compartment (hereafter referred to as the “double-cells”) instead of a conventional single compartment cell (single-cell), which yields amorphous FeCrNi (a-FeCrNi). Firstly, the microstructure and recrystallization behavior of FeCrNi electrodeposits from the single-cell and the double-cells are characterized and compared. The grazing-incidence XRD (GI-XRD) revealed that as-deposited FeCrNi films prepared in the double-cell is nanocrystalline consisting of the metastable ferrite phase. The analysis of TEM shows that the size of grain is about 7 nm. Further investigation of the microstructure was performed by the in-situ GI- XRD during thermal treatment up to 800°C. The experiments demonstrate that nc-FeCrNi recrystallizes at 550°C along with its phase transformation from the ferrite to the austenite. On the other hand, a-FeCrNi was shown to undergo recrystallization to form primarily the ferrite phase, which is subsequently transformed to the austenite phase. Chemical analysis of deposits revealed that the carbon content of nc-FeCrNi is significantly lower than that of a-FeCrNi, suggesting that the carbon inclusion is responsible for the formation of amorphous phase. The major source of carbon is attributed to reaction compounds at the anode electrode. In order to identify the anodic reactions in our FeCrNi electroplating bath, a series of cyclic voltammetry was carried out. The electrochemical study shows the evidence of the anodic oxidation of glycine as well as the oxidation of ferrous and trivalent chromium ions to ferric and hexavalent chromium ions on a Pt anode. Therefore, the oxidation products of glycine or the compounds generated by their further reactions are thought to be responsible for the inclusion of carbon. In this presentation, we will also discuss the corrosion properties of nc- and a-FeCrNi deposits along with the micromechanical properties of these FeCrNi electrodeposits.
1. Philippe, L., C. Heiss, and J. Michler, Electroplating of stainless steel. Chemistry of Materials, 2008. 20(10): p. 3377-3384.