Formation of a Ni-Al intermetallic compound layer by AIH-FPP treatment

In order to form a Ni-Al intermetallic compound layer on a carbon steel surface, Atmospheric-controlled Induction Heating Fine Particle Peening (AIH-FPP) was carried out at 900°C in argon atmosphere with nickel and aluminum particles mechanically milled by planetary ball mills. The treated surface was analyzed using a scanning electron microscope (SEM), an energy dispersive X-ray spectrometer (EDX), and an X-ray diffraction (XRD). Oxidation tests were carried out at 900°C for 100 hours. Results showed that the Ni-Al intermetallic compound layer with a thickness of 200 mm was formed in the case of the specimen treated by the aluminum rich shot particles; the ratio of Ni to Al was 1 to 4 (mol). This was because (i) melted aluminum particles decreased the melting point of nickel particles and the steel substrate, and (ii) partially melted area promoted a combustion synthesis reaction between nickel and aluminum, resulting in forming the Ni-Al intermetallic compound layer. The AIH-FPP treated surface showed a higher oxidation resistance than that of the un-treated specimen. This was because Al₂O₃ continually created from the Ni-Al intermetallic compound layer protected the steel substrate.