STRUCTURE MORPHOLOGY OF Fe-Al COATING DETONATION SPRAYED ONTO CARBON STEEL SUBSTRATE

摘要

The morphology of Fe-Al type intermetallic coatings produced by detonation spraying on a 045 steel substrate was described based on the microstructure analysis using transmission electron microscopy (TEM), and selected area electron diffraction (SAED) techniques as well as an analysis of chemical composition in microareas (EDS). The TEM was useful in establishing the coating structure in the vicinity of the interface between the substrate and the coating up to the depth of 10 m. Starting from the boundary with the substrate, an amorphous phase (A), then columnar crystals (CC) followed by crystalline grains of Fe_3Al were observed. Farther on, the amorphous phase again and grains of the FeA12 phase were localized. The Fe_2Al_5 and Fe_3Al phases lay close to the coating surface. The phase transformations were completed with calorimetric analysis, which showed heat effects typical for magnetic transformations and ordering. The results indicated to the mechanism of coating formation which consisted in partial melting of the Fe-Al starting powders and the formation of the amorphous phase, unidirectional solidification of the columnar phases and the deposition of the remaining not melted Fe-Al powder. Next, partially melted material was deposited.