In order to increase surface hardness of AISI 1045 steel, a new hybrid surface modification; combination of atmospheric-controlled induction-heating fine particle peening (AIH-FPP) and plasma nitriding, was developed. Surface microstructures of plasma nitrided specimens pre-treated with AIH-FPP using Cr shot particles were characterized by an optical microscope, a scanning electron microscope (SEM), an energy dispersive X-ray spectrometer (EDX) and X-ray diffraction analysis (XRD). As results, the nitrided layer was formed at the surface of the specimen with Cr diffused layer induced by AIH-FPP. This nitrided layer showed higher hardness than that of without AIH-FPP specimen. This was because CrN was formed at the surface of the AIH-FPP/Plasma nitriding treated specimen. And, the surface hardness of the nitrided layer tended to increase as the Cr concentration in the surface layer decreased. It was clarified that the pore formation during the AIH-FPP/Plasma nitriding treatment was inhibited by decreasing Cr concentration. These results suggest that the proposed hybrid surface treatment remarkably increases surface hardness of AISI 1045 steel.

A new surface treatment system (IH FPPsystem) combined with an induction heating and a fine particle peening machine were developed. FPP treatments were carried out on structural steel discs by using Cr shot particle at room temperature, 400°C, 600°C and 900°C. After characterizing the surfaces by SEM, EDX and XRD, corrosion tests were performed by a three electrode method using a computer driven potentiostat. No noticeable differences were observed on the specimen treated at RT, 400°C and 600°C. In the case of the specimen treated at 900°C, however, higher corrosion resistance which is almost the same as FPP treated stainless steel (SUS316L) was observed. This was because Cr diffused layer covered with relatively smooth oxidized surface prevented a corrosion reaction in 3NaCl environment.

In the present study, gas blow IH (Induction Heating) nitrided specimens were produced under variable nitrogen gas blowing velocities. This was done to investigate the effects of nitrogen gas velocity on the surface properties of Ti-6Al-4V alloy. The surface properties of the specimens were characterized using X-ray diffraction, scanning electron microscopy, a micro-Vickers hardness tester and nano-indentation tester. The results showed that the surface hardness and thickness of the hardened layer increased with increasing gas blowing velocity. This occurred because of the elevated temperatures in the interior of the alloy relative to the surface temperatures at a higher gas blowing velocity. Furthermore, increasing the magnetic eld strength around the IH coil and the eddy current density around the circumference of the specimen also accelerated the formation of a hardened layer on the surface of the titanium alloy. Consequently, a high-hardness layer can be formed by applying a treatment temperature less than the β transus of the Ti-6Al-4V alloy, while increasing the gas blowing velocity. This layer improves the wear resistance of the alloy by suppressing both grain coarsening and the formation of an acicular α phase.

In order to form a Ti-Al intermetallic compound layer on a carbon steel surface, an atmospheric-controlled induction heating fine particle peening （AIH-FPP） treatment was performed at 1000℃ in argon atmosphere. The shot particles were prepared by a mechanical milling method. Titanium and aluminum particles at molar ratios of one to three were mechanically milled by a planetary ball mill for 6 h. The treated surface was analyzed using a scanning electron microscope, an energy dispersive X-ray spectrometer and X-ray diffraction. The reciprocating dry wear tests were performed under the following conditions; an opposing material of alumina balls of 3 mm in diameter, a load of 2.0 N, a sliding speed of 600 mm/min and a sliding distance of 224 m. The results showed that a Ti-Al intermetallic compound layer consisting mainly of TiAl 3 formed on the surface of carbon steel by AIH-FPP treatment. This was because the shot particles were transferred to the substrate and the aluminum and titanium in the particles reacted neither excessively nor insufficiently. The AIH-FPP treated surface showed a higher wear resistance than that of the untreated surface. This was because the wear mode of carbon steel changed from abrasive wear to adhesive wear owing to the formation of the Ti-Al intermetallic compound layer on the surface.

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 Al 2 O 3 continually created from the Ni Al intermetallic compound layer protected the steel substrate.