Increasing surface hardness of AISI 1045 steel by AIH-FPP/plasma nitriding treatment

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.