Abstract
The relation between fatigue strength and micro-structure of tufftrided mild steel (SS 41, S 15CK) has been studied by means of fatigue test, optical and electron micrography, the hardness test and X-ray diffraction. The results obtained are summarized as follows:
(1) Fatigue strength of SS 41 by a Schenck fatigue tester is increased with tufftriding time.
(2) S 15 CK tufftrided specimens are examined by Ono fatigue tester. It’s strength is reduced by tempering.
(3) According to tempering conditions, two types of plate-like nitride are precipitated in the diffusion zone. The larger one is γ′-Fe4N and the smaller is α″-Fe16N2.
(4) In addition to fatigue striations and rub marks, tire tracks are observed in the diffusion zone of the fracture surface.
