预腐蚀与预疲劳对30CrMnSiA 螺栓钢微动疲劳行为的影响

To investigate the fretting fatigue behavior of 30CrMnSiA high-strength bolt steel under marine environmental service conditions, the influence and mechanism of pre-corrosion, pre-fatigue, and their combined effects on the fatigue damage behavior of 30CrMnSiA high-strength steel were studied by using analysis methods such as scanning electron microscopy, energy dispersive spectroscopy, electrochemical impedance spectroscopy. The results showed that, under the experimental conditions here, the damage mode of 30CrMnSiA high-strength bolt steel is fretting fatigue. With the increase of pre-corrosion time, the fretting fatigue life of 30CrMnSiA high-strength bolt steel gradually decreased, and the average fretting fatigue life of bolts decreased by 73. 69% after 6 days pre-corrosion. Under the same pre-corrosion experimental conditions, as the number of pre-fatigue cycles increased, the fretting fatigue life of bolts gradually decreased;however, the fretting fatigue life of bolts with 10 000 pre-fatigue cycles and 2 days of pre-corrosion is a little higher than that of bolts with only 2 days of pre-corrosion. The more pre-fatigue cycles and the longer the pre-corrosion time, the bolt had shorter fretting fatigue life. After 40 000 cycles of pre-fatigue and 4 days of corrosion, the fatigue life of bolts decreased by 86. 4%. The reason was that pre-corrosion and its combined effect with pre-fatigue usually promoted the initiation and propagation of fatigue cracks on the surface of 30CrMnSiA high-strength bolt steel, which led to a reduction of their fretting fatigue life. However, when the pre-fatigue cycle was small, micro wear was lighter and had a certain leveling effect on the bolt surface, thereby alleviated the adverse effects of corrosion. As a result, the fretting fatigue life of bolts is slightly longer than that of simply pre-corrosion bolts.