Synthesis of Al-Ni Coatings by Pack Cementation and Examination of Their High Temperature Oxidation Resistance.

Carbon steel is one of the most commonly used metals in the construction and industrial sectors due to its very good mechanical properties [1]. However, it oxidizes quickly and easily, in elevated temperature and corrosive environments [2]. Nickel aluminum alloys are known to exhibit resistance to high temperature [3]. In this work Al-Ni coatings were developed by a combination of two processes. An initial Ni layer was electrochemically deposited on steel followed by aluminization by pack cementation. Al-Ni alloys were formed on the top of the coatings followed by a layer of pure Ni. At the same time Ni interdiffused in the ferrous substrate creating Ni-Fe compounds, increasing the coating adherence. The structure and phase identification were performed using X-ray diffraction, while the morphology and elemental analysis was examined by Scanning electron microscopy. Non-isothermal and isothermal thermogravimetric measurements were performed on the coated and uncoated samples in order to define the critical oxidation temperatures and evaluate the thermal resistance at long lasting exposures. [ABSTRACT FROM AUTHOR]