TY - JOUR
T1 - Effect of ultrasonic nanocrystal surface modification on the fatigue behaviors of plasma-nitrided S45C steel
AU - Wu, Bo
AU - Wang, Pangpang
AU - Pyoun, Young Shik
AU - Zhang, Jianxun
AU - Murakami, Ri ichi
N1 - Funding Information:
The authors thank Atsushi Onizawa of Neturen Company for the plasma nitriding assistance and DesignMecha Co., Ltd for the UNSM assistance. This study was supported by the Double Degree Program (DDP) of the University of Tokushima .
PY - 2012/12
Y1 - 2012/12
N2 - An ultrasonic nanocrystal surface modification (UNSM) technique with different striking numbers (34,000mm-2 and 69,000mm-2) was employed to modify the surface of plasma-nitrided S45C steel. After the UNSM treatment, the fatigue strength of the 8h plasma-nitrided specimen (N8) was clearly improved, and the sub-surface cracks were nearly restrained, while the 48h plasma-nitrided specimen (N48) showed no improvement of fatigue strength. The mechanical properties of the specimens before and after UNSM treatment were characterized, such as the microhardness, the surface roughness, and the surface compressive residual stress. A grain refinement layer was formed on the surface of the specimens due to the severe plastic deformation induced by the dense striking, and the grain distribution was analyzed by using X-ray diffraction. The grain refinement layer played an important role in the improved mechanical properties. The fatigue limit enhancement mechanism was examined by analyzing the stress intensity factor from fish-eye cracks. For the fish-eye cracks, the stress intensity factor in the facet area, Kfacet, was found to be a constant value of approximately 4.08MPa.m1/2, regardless of either the UNSM treatment or the nitriding duration.
AB - An ultrasonic nanocrystal surface modification (UNSM) technique with different striking numbers (34,000mm-2 and 69,000mm-2) was employed to modify the surface of plasma-nitrided S45C steel. After the UNSM treatment, the fatigue strength of the 8h plasma-nitrided specimen (N8) was clearly improved, and the sub-surface cracks were nearly restrained, while the 48h plasma-nitrided specimen (N48) showed no improvement of fatigue strength. The mechanical properties of the specimens before and after UNSM treatment were characterized, such as the microhardness, the surface roughness, and the surface compressive residual stress. A grain refinement layer was formed on the surface of the specimens due to the severe plastic deformation induced by the dense striking, and the grain distribution was analyzed by using X-ray diffraction. The grain refinement layer played an important role in the improved mechanical properties. The fatigue limit enhancement mechanism was examined by analyzing the stress intensity factor from fish-eye cracks. For the fish-eye cracks, the stress intensity factor in the facet area, Kfacet, was found to be a constant value of approximately 4.08MPa.m1/2, regardless of either the UNSM treatment or the nitriding duration.
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U2 - 10.1016/j.surfcoat.2012.10.063
DO - 10.1016/j.surfcoat.2012.10.063
M3 - Article
AN - SCOPUS:84870255242
SN - 0257-8972
VL - 213
SP - 271
EP - 277
JO - Surface and Coatings Technology
JF - Surface and Coatings Technology
ER -