ラジカル窒化したSNCM439鋼の疲労強度に及ぼす化合物層の影響

概要

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Rotating bending fatigue tests were carried out for a radical nitrided SNCM 439 steel in order to investigate the influence of compound layers on the fatigue strength and fracture mechanism. By nitriding at 480℃ to the steel quenched at 835℃ and tempered at 160℃, the fatigue strength increased, though the internal matrix softened and the static strength decreased. In both of the nitrided steel and the quench-tempered steel, fish-eye fracture occurred in long life region, and the fracture initiated from a specimen surface in short life region. By removing the compound layers in the nitrided steel, the fatigue strength decreased dramatically and the fracture origin changed from a subsurface to a specimen surface. That is, compound layers make the fatigue life increase through both of the suppression of the initiation of a surface crack and the change of fracture origin.
社団法人日本機械学会の論文
2003-10-25