Carbon steel is the most important engineering alloys due to low production costs and a wide range of engineering properties. However, carbon steel has weak tribological properties and low hardness. Application of high resistant coatings on the steel surface is the best solution to improve its tribological properties. In this study, the mechanical milling method was used to form nanocomposite coatings of FeAl and FeAl /Al 2 O 3 on the Ck45 steel surface. Mechanical milling at ambient temperture leads to surface work hardening, mechanical activation and formation of nanostructured coating. In this method substrate and milling balls are placed in the bowl and coating is produced on substrat as a result of ball impacts. In this study, the balls was 4mm in diameter and ball- to- powder weight ratio was 10:1. Milling time was 2 to 22 hours. Prepared samples after ball milling were subjected to annealing treatment at 500 o C for 1 to 3 hours. Effects of the annealing treatment on structure, hardness, roughness and phase changes was investigated. The coatings were examined using X-ray diffraction, scanning electron microscopy (SEM), roughness measurements, microhardness and microscratch tests. The results showed that the best coating with proper structure and surface uniformity was formed by using balls with 4mm diameter and ball-to-powder weight ratio of 10:1 after 14 hours for FeAl and after 18 hours for FeAl / Al 2 O 3 . With increasing milling time, FeAl coating thickness increased to 78µm with a hardness of 870Hv and FeAl / Al 2 O 3 coating thickness increased to 98µm with a hardness of 1050Hv. Annealing treatment at 500 o C for 3 hours improved the coating adhesion and microhardne properties due to the formation of FeAl and FeAl / Al 2 O 3 . Uniformity and structural properties of FeAl/Al 2 O 3 nanocomposite coating was enhanced compared to the FeAl coating due to Al 2 O 3 particle. Keyword: Coating, Intermetallic compound FeAl, Nanostructured materals, Mechanical alloying, Nanocomposite
