Effect of process parameters on the formation of nanostructured Ni-Al coating on carbon steel by using mechanical alloying

In the present study, formation of the nanostructured NiAl intermetallic coatings on carbon steel by MA method was studied. The composition of Ni-Al powder with an atomic ratio of 1:1 with different ball size, ball-to powder weight ratio and milling duration were used. The substrate, fixed at the top of a vibration chamberd. During mechanical alloying process, the substrate surface was subjected to high-energy ball impacts. Powder particles trapped between the ball and cold welding occurred at surface. After that, synthesized samples were annealed. Thickness and hardness of coating optimized with factors ball size, ball-to-powder weight ratio and milling duration. The cross-section of the coated substrate was investigated using X-ray diffraction and scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the formation of Ni-Al intermetallic coatings were achievable. By increasing milling duration the thickness of the Ni-Al coatings significantly increased and the layered or pancake-type structure of the coating consolidate into a bulk material. Best coating was formed with ball 4mm diameter and ball to powder weight ratio of 10:1. The milling duration increases to 480 minutes and particle size reduced to 28nm.