Spray deposition of an iron aluminide

High velocity oxyfuel (HVOF) spray forming of an iron aluminide [Fe12.5 Al- 2.93 Ni-0.02 B (wt %), containing 300 p.p.m. oxygen], followed by heat trea tment for 24 h at 500 degrees C, 18 h at 600 degrees C and 20 min at 800 de grees C, and multipass hot rolling at 800 degrees C has been studied. Three different thicknesses (0.43, 0.93 a nd 1.33 mm) of sprayed de posit we re produced by spraying for different times (approximately 10, 20 and 30 min). The spray-deposited layers exhibited some oxide and some porosity. This po rosity was reduced by heat treatment. The as deposited layer had a high deg ree of B2 order, and a B2 antiphase domain size of 4.5 nm. On hot rolling t his 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 rol ling route. In heat treatment, the aluminide-sprayed layer formed a non-pro tective Fe2O3 oxide, rather than the usual Al2O3 that forms on the binary a lloy. This is attributable to the Ni content of the iron aluminide powder e mployed. (C) 1998 Kluwer Academic Publishers.