Formation of Intermetallic Compounds Fe-Al on Steel by Ball Milling and Thermal Treatment

In this study, by mechanical alloying method with a powerful bullet milling machine (SPEX) was used to create aluminum coating on the simple carbon steel surface (Ck 45) Balls with diameter of 4mm with a total weight of 50g and 5g aluminum powder with 99.99% purity, the size of smaller particles than 150μm and weight of 5g with (Ck 45) steel specimen were 8×8 mm with a thickness of 3mm were put into the milling chamber and milled for different times from 10min to 30h at room temperature. As-milled samples were annealed at 550˚C at different times (2, 4, 6, 8, 10, 30h) to evaluate the formation of Fe-Al intermetallic compounds, and the effect of thermal treatment coating properties such as: adhesion rate, fuzzy changes thickness of intermetallic compounds surface were investigated. Structures of the produced coating were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), spectrometry and micro hardness test. The results showed that the best coating in terms of micro structural properties and uniformity was created after 80 min ball milling. The results of the thermal treatment at a constant temperature of 550˚C for 30h showed that the interface between the aluminum coating and the steel substrate is formed and has a thickness of 28 micrometer. Furthermore the micro hardness test was carried out on the coated samples and results showed that the coating after the 80 min alloying, before thermal treatment had a low hardness of about 75 Vickers after performing the thermal treatment for 30h, the hardness of coverage in the interface of Fe/Al was increased to 471 Vickers.