零夹杂42CrMo高强钢的超长寿命疲劳性能

FATIGUE PROPERTY OF ULTRA-LONG LIFE OF HIGH STRENGTH 42CrMo ZERO-INCLUSION STEEL

利用超声疲劳实验方法研究了2种商业42CrMo钢和2种零夹杂42CrMo钢在不同热处理制度下的超长寿命疲劳性能.结果表明,42CrMo钢疲劳S-N曲线在106-109cyc范围内无平台出现,疲劳极限消失;零夹杂42CrMo钢在此寿命区间有明显的疲劳极限. SEM断口观察表明,42CrMo试样疲劳开裂大多起源于非金属夹杂物,而零夹杂42CrMo全部起源于基体表面.零夹杂42CrMo钢的最大特点是在2×106-109cyc内不易发生疲劳断裂,疲劳寿命的可靠性显著增加.

The ultra-long fatigue properties of four high strength 42CrMo steels, two of commercial and two of zero-inclusion, produced by different heat treatment procedures are studied. The experimental results illustrate that in the regime of 10(6)-10(9) cyc, two commercial steels have no horizontal asymptote in fatigue S-N curves, so the conventional fatigue limit eliminates, but the fatigue limit of two zero-inclusion steels exists. SEM analysis shows the fatigue crack initiates from nonmetallic inclusion for commercial 42CrMo steels, and from surface of the matrix for two zero-inclusion steels. In the regime of 2 x 10(6)-10(9) cyc, it is very difficult to fracture for zero-inclusion steels, and the reliability of fatigue life is substantially improved.