Boriding of nickel aluminide

Boriding of Ni3Al was carried out with Ekabor–Ni powders at temperatures between 1073 and 1223 K for 2, 4, 6 and 8 h. The characterization of boride layer formed on the surface of nickel aluminide substrates were identified by optical microscopy and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and wave length dispersive spectroscopy (WDS). The presence of boride Ni3B and Ni4B3 on the Ni3Al substrate was confirmed by X-ray diffraction (XRD) analysis. Microhardness and thickness of boride layers were measured. Its hardness was found to be in the range of 780 to 1150 ± 15 HV. Depending on process temperature and boriding time the thickness of coating layers ranged from 12 to 70 ± 3 µm. A parabolic relationship was observed between the layer thickness and the process time. The activation energy for process was calculated as 188, 8 ± 14.4 kJ/mol.