Microstructures and properties of NiAl-TiC nanocomposite coatings on carbon steel surfaces produced by mechanical alloying technique

TiC reinforced NiAl intermetallic matrix composite coatings on carbon steel plate were fabricated by using mechanical alloying of Ni-Al-TiC powders. The process involved trapping powder particles between the ball and cold welding together at surface. Coatings were examined using X-ray diffraction, scanning electron microscopy (SEM) and the energy dispersive X-ray spectrometry (EDS) and transmission electron microscopy (TEM). The results indicated that the volume fraction of NiAl-TiC nanocomposite phase increases with increasing mechanical alloying time. In the sample milled for 480 min, only NiAl peaks were observed. EDS analysis showed uniform distributions of the Ni, Al and Ti in nanocomposite. The nanocomposite formation was the result of mechanical mixing of the Ni-Al and the TiC nanoparticles. The composite coatings had the features of high quality metallurgical bonding with the substrate and proper hardness. The size of nanocrystalline grain size in the NiAl coating ranged between 21 nm and 110 nm. The average thickness of the coating layers at 480 min was 620 μm. The hardness of the composite coating was five times as high as that of the initial steel plate.