Ultra-fast boriding of nickel aluminide

In this study, we explored the possibility of ultra-fast electrochemical boriding of nickel aluminide (Ni3Al) in a molten borax electrolyte. Electrochemical boriding was performed at 950 degrees C for 15 min and at current densities ranging from0.1 to 0.5 A/cm(2). The boride layers formed on the test samples were 50 to 260 mu m thick depending on the current density. The mechanical, structural, and chemical characterization of the boride layers was carried out using a Vickers micro-hardness test machine, optical and scanning electron microscopes, and a thin film Xray diffractometer. The hardness of boride layer was in the range from 800 to 1200 +/- 50 HV depending on the load and the region from which the hardness measurements were taken. X-ray diffraction studies confirmed that the boride layers were primarily composed of Ni3B, Ni4B3 and Ni20AlB14 phases. Structurally, the boride layer was very homogenous and uniformly thick across the borided surface area. (C) 2011 Elsevier B.V. All rights reserved.