Spray deposition of an iron aluminide

Abstract

High velocity oxyfuel (HVOF) spray forming of an iron aluminide [Fe–12.5 Al–2.93 Ni–0.02 B (wt%), containing 300 p.p.m. oxygen], followed by heat treatment for 24 h at 500°C, 18 h at 600°C and 20 min at 800°C, and multipass hot rolling at 800°C has been studied. Three different thicknesses (0.43, 0.93 and 1.33 mm) of sprayed deposit were produced by spraying for different times (approximately 10, 20 and 30 min). The spray-deposited layers exhibited some oxide and some porosity. This porosity was reduced by heat treatment. The as deposited layer had a high degree of B2 order, and a B2 antiphase domain size of 4.5 nm. On hot rolling this material to a reduction of 38%, it was found to be more susceptible to edge cracking than similar material processed by an ingot–extrusion–hot rolling route. In heat treatment, the aluminide-sprayed layer formed a non-protective Fe2O3 oxide, rather than the usual Al2O3 that forms on the binary alloy. This is attributable to the Ni content of the iron aluminide powder employed. © 1998 Kluwer Academic Publishers