Formation of nanostructured NiAl coating on carbon steel by using mechanical alloying

Abstract

Nanostructured NiAl intermetallics coatings were generated on carbon steel by using mechanical alloying in ambient temperature and pressure. Ni and Al powders were mixed with the composition of Ni–50at% Al. The process involved powder particles trapped between the ball and cold welding at surface. Coatings were examined using X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the phase transmutation during process and subsequent heat treatment are strongly dependent on mechanical alloying time. After 480min heat treatment of mechanically alloyed sample, only NiAl peaks were viewed. Ball encounters and failures consecutively reduced the coarse grains of the coating to the nanoscale. The size of nanocrystalline grains in the NiAl coating ranged between 28 and 130nm. The creation of the coatings was studied at milling intervals between 60 and 600min. The average thickness and hardness of the surface layers at 480min, were 470μm and 930HV, respectively.