空气和腐蚀环境下双相不锈钢SAF2507的疲劳性能

Fatigue Properties of Duplex Stainless Steel SAF2507 Under Air and Corrosive Environments

对超级双相不锈钢SAF2507分别在空气和3.5%NaCl溶液中进行旋转弯曲疲劳实验,研究两种介质下SAF2507不锈钢的疲劳性能。结果表明:宏观上,双相不锈钢SAF2507在3.5%NaCl腐蚀环境中的疲劳强度较空气中的下降幅度小,为空气下的90%。但微观上,空气中疲劳断口表现为韧性断裂,在铁素体和奥氏体相上呈现大量疲劳辉纹;腐蚀环境下,奥氏体为韧性断裂,而铁素体呈现解理断裂模式。两相上疲劳辉纹的宽度和间距随着晶粒位向及二次裂纹的开裂而不同。在奥氏体-铁素体双相不锈钢的疲劳断口中,不能根据疲劳辉纹的间距进行相的鉴别。

Rotating bending fatigue tests were conducted on the super duplex stainless steel of SAF 2507 to investigate fatigue properties in both air and 3. 5% NaC1 aqueous environment. The results show that on the macro scale, compared to the air fatigue, there is no significant reduction in the fa- tigue strength of SAF2507 under corrosive environment, which is 90% of the air fatigue strength. But on the micro scale, the fatigue failure exhibits ductile fracture with fatigue striations observed in both ferrite and austenite in air. While in 3.5% NaCl, austenites have ductile fracture and ferrites exhibit cleavage fracture mode. The width and space between fatigues striations vary with grain orientations and second cracks, indicating that ferrite and austenite phase on fracture surface could not be identified simply by fatigue striations space.