An atmospheric controlled IH FPP (Induction Heating and Fine Particle Peening) treatment system was developed. Using the system, the surface of ordinary structural steel was modified with Cr shot particle at room temperature, 500°C, 700°C and 900°C in atmosphere of either argon and air. The treated surfaces were characterized using a scanning electron microscope (SEM), an energy dispersive X ray spectrometer (EDX), an X ray diffractometer (XRD) and an X ray photoelectron spectroscope (XPS). In the case of the specimen treated in argon atmosphere, a relatively thick and uniform Cr rich layer was formed at the surface. The thickness of the layer was changed with an increase in temperature, the higher the temperature, the thicker the layer. In the case of the specimen treated in air, however, an oxidized scale was formed on the treated surface instead of a Cr rich layer. The results of the experiments prove that atmospheric controlled IH FPP treatment successfully creates a Cr rich surface layer. The specimen treated by atmospheric controlled IH FPP showed higher corrosion resistance compared to that of the untreated specimen, the higher the thickness of the Cr rich layer, the higher the corrosion resistance.

In order to improve the fatigue properties of SCM435H steel, a surface treatment system was developed that combines high-frequency induction heating (IH) with fine particle peening (FPP). In this IH-FPP system, a compressed air spray from the FPP nozzle rapidly cools the specimen surface, which is pre-heated by the IH system. The specimen surface can be simultaneously modified by plastic deformation and quenching. The IH-FPP process was performed at temperatures ranging from 400-750 . Vickers hardness and residual stress distributions were measured in order to examine the characteristics of the surface-modified layer created by the developed process. Surface microstructures were also observed using an optical microscope. As a result, the developed processes from 650-750 created a surface with a high hardness and an extremely fine-grained microstructure. The fine-grained microstructure was created due to dynamic recrystallization. In order to clarify the effects of the IH-FPP treatment on fatigue strength of notched SCM435H steel with a stress concentration factor of Kt = 2.36, fatigue tests were performed at room temperature using a rotational bending fatigue testing machine. The specimen treated by IH-FPP process at 700 exhibited the highest fatigue strength. This was because micro crack initiation and propagation were inhibited by the surface modified layer with high hardness and fine-grain. This result suggests that the IH-FPP treatment process is highly effective in improving the fatigue strength of steel.

In this study, in order to accelerate the diffusion of nitrogen into austenitic stainless steel, fine particle peening (FPP) was introduced prior to gas nitriding. The effects of the FPP treatment on gas nitriding behavior, and consequent corrosion and fatigue properties of austenitic stainless steel (SUS316) were evaluated. Gas nitriding was performed at 400°C, 475°C and 550°C. The microstructural characteristics of the treated specimens were examined using a micro-Vickers hardness tester, optical microscope, scanning electron microscope (SEM), Glow discharge optical emission spectrometry (GD-OES), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). It was revealed that nitrided layer was formed on the FPP-treated surface although passive film existed at the surface. This was because nitrogen diffused into the material through the transferred particles on the surface during the subsequent gas nitriding process. In order to evaluate the corrosion resistance, electrochemical corrosion tests were performed. The specimen nitrided at 400°C showed highest corrosion resistance due to the existence of an S-phase. Fatigue tests were also performed at room temperature using a rotational bending fatigue testing machine. The nitrided specimens pre-treated with FPP showed the higher fatigue strength compared with single surface treated specimens.

In this study, in order to increase surface hardness of S45C steel, hybrid surface modification treatment which is a combination of atmospheric controlled induction heating fine particle peening (AIH FPP) and gaseous nitriding, were developed. Surface microstructures of gaseous nitrided specimens pre treated with AIH FPP were characterized by a scanning electron microscope (SEM), an energy dispersive X ray spectrometer (EDX), X ray diffraction analysis (XRD) and X ray photoelectron spectroscopy (XPS). In the case of the AIH FPP treated specimens with a Cr transferred layer, the nitrided layer was not formed. This was because diffusion of nitrogen into the surface of the specimens was disturbed by chromium oxide in the transferred layer. On the other hand, the nitrided layer was formed at the surface of the specimen with Cr diffused layer induced by pre AIH FPP, and this nitrided layer showed higher hardness than that of the specimen without AIH FPP. However, the surface hardness decreased near the surface. In order to suppress decreasing of the surface hardness, the specimens with different Cr concentrations were prepared. It was clarified that the surface hardness was affected by Cr concentration in the Cr diffused layer; the lower the Cr concentration, the higher the surface hardness. It was assumed that the pore formation during nitriding process was inhibited by decreasing Cr concentration. These results suggest that surface hardness of S45C steel remarkably increases by hybrid surface treatments of AIH FPP and gaseous nitriding.

The effect of a fine particle peening (FPP) on atmospheric oxidation behavior and tribological properties of Ti 6Al 4V alloy was evaluated. Surface microstructures of oxidized specimens pre treated with FPP were characterized using scanning electron microscope (SEM), energy dispersive spectrometry (EDS), glow discharge optical emission spectrometry (GDOES) and X ray diffraction (XRD). The oxide layer formed on the oxidized specimen pre treated with FPP was thicker than that on the oxidized only specimen, because the microstructure induced by FPP facilitated the diffusion of oxygen and aluminum elements during the oxidation process. As results of reciprocating sliding wear tests, width of wear track on the oxidized specimen pre treated with FPP was shallower compared to the oxidized only specimen. Moreover, the oxide layer formed at the oxidized only surface was delaminated during tests, otherwise there was no delamination at the oxidized surface pre treated with FPP. This was because the surface oxide layer exhibited good interface adherence due to the existence of a thick oxygen solid solution layer. These results indicate that the modified layer created by the combination process of FPP and atmospheric oxidation is effective to improve the wear resistance of titanium alloys.