求翻译：cryogenic treatment, the resistance to S-N fatigue either does not improve with cryogenic treatment or significantly decreases with Ti-nitriding treatment. From the fractographic and micrographic analyses in Figures 4, 5 and 6, it was observed that Ti-nitriding produces porous surface structure, which encourages easy fatigue crack initiation on the surface area. It is well known that approximately 40 to 60% of total cycles to failure is used for the initiation of crack [11]. With the formation of porous surface structure,是什么意思？

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