Diffusion treatment of Ni-B coatings by induction heating to harden the surface of Ti-6Al-4V alloy

Electroless nickel-boron coatings on Ti-6Al-4V alloy were obtained by immersion in nickel chloride aqueous solutions with sodium borohydride. The diffusion treatments were carried out by induction heating using a superficial magnetic field intensity (current in the coil) that allows to achieve a surface temperature of 1020 degrees C in 100 s. The effect of induction heating on microstructure and mechanical properties of the Ni-B coated samples were evaluated by SEM, energy dispersive X-ray spectroscope (EDS), wavelength-dispersive spectrometry (WDS), glow discharge optical spectrometer (GDOS) and microhardness testing and the results were compared with those obtained previously by heat treatments in oven at 800 degrees C for 40 h. Surface hardness higher than 900 HV100 and depth of hardening thicker than 300 mu m were achieved by diffusion of the Ni-B layer carried out by induction heating. (C) 2008 Elsevier B.V. All rights reserved.