Fe-based amorphous-nanocrystalline thermal spray coatings

Abstract

In this work, a new composition of Fe-15Cr-4Mo-5P-4B-1C-1Si (wt.%) amorphous powder was produced by mechanical alloying of elemental powder mixture. Thermal spraying of amorphous powder was done by high velocity oxy fuel spraying technique at various spraying conditions to obtain the desirable amorphous and nanocrystalline coatings. It was found that α-Fe based supersaturated solid solution is first formed during mechanical alloying which transforms to amorphous structure at longer milling times. The crystallization kinetic parameters suggest that the crystallization mechanism is dominantly governed by a three-dimensional diffusion-controlled growth. The crystallization of amorphous structure occurs in one single stage. By carefully controlling the spraying parameters and proper selection of powder composition, the desired microstructure with different fraction of amorphous and nanocrystalline phases and therefore with different properties could be obtained.