Development of Ni–Al and Ni–Al–Fe intermetallic coatings on carbon tool steels

Abstract

Intennetallic coatings of Ni–Al and Ni–Al–Fe have been developed on carbon tool steel substrates. Nickel coatings with thicknesses of 20 and 40 f.1m were deposited on prealuminised specimens. Diffusion annealing was subsequently carried out at a temperatureof 1050oe. The optimum diffusion time for each thickness was selected based on trends in the hardness profile. The microstructure and phases developed in the coating were identified by metallography, microhardness, X-ray diffraction, energy dispersive X -ray microanalysis, and glow discharge optical spectroscopy techniques. Experimental results indicate that a three layer coating was formed on the surface of the diffusion annealed, aluminised, and nickel coated specimens after optimum diffusion time. The intermetallic compound layers of Ni₃Al and NiAl were formed on the surface and FeAl and Fe₃Al layers beneath them.