Annealing Effect on the Intermetallic Compound Formation of Cold Sprayed Fe/Al Composite Coating

A Fe/Al composite coating was prepared by cold spraying using an iron-aluminium powder mixture with a Fe/Al atomic ratio of 1:1. The effect of annealing temperature on the intermetallic compound formation in the cold-sprayed Fe/Al coating was investigated. The as-sprayed and annealed coatings were characterized by x-ray diffraction (XRD), and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy. Results showed that intensive particle deformation on impact promoted the Fe2Al5 intermetallic compound formation at a low annealing temperature of 450 °C and this intermetallic layer firstly appeared along some intimate contact regions at the aluminium-iron boundaries. The amount of the Fe2Al5 intermetallic compound increased and no other intermetallic compound phases appeared when the annealing temperature was raised from 450 to 600 °C. Some cracks developed in the Fe2Al5 intermetallic layer when the coating was annealed at 600 °C and the possible causes leading to evolution of cracks are discussed.