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

Abstract

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 °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 °C for 40 h. Surface hardness higher than 900 HV 100 and depth of hardening thicker than 300 μm were achieved by diffusion of the Ni–B layer carried out by induction heating.