对铸造镍基高温合金M38在900℃下的低周疲劳行为进行了研究. 实验采取轴向总应变控制, 应变比为-1, 应变速率为1×10-2s-1. 实验结果表明: M38在900℃下具有与IN738LC接近的疲劳性能. 在高应变幅时, 疲劳裂纹主要萌生在表面碳化物等应力集中处;在低应变幅时, 氧化对裂纹的萌生起重要作用, 疲劳裂纹主要萌生于易于优先氧化的表面晶界和碳化物等处. 在所有应变幅下, 疲劳裂纹均沿着垂直应力轴的方向穿晶扩展.
Low cycle fatigue tests of cast nickel base superalloy M38 have been conducted at 900℃ in air under fully reversed total strain control, and the strain rate is 1×10-2s-1. After failure, the fracture surfaces and longitudinal sections of the specimens were examined using a scanning electron microscope. Experimental results revealed that the fatigue property of M38 is similar to that of IN738LC. At high strain amplitudes, crack tends to initiate at stress concentration sites such as surface carbides. While at low strain amplitudes, oxidation takes significant effect on crack initiation. The Cr-rich surface-connected grain boundaries (G.B.) and Ti-rich surface-carbides were observed to be favorable crack initiation sites. Under all strain amplitudes, the crack propagation mode is transgranular.
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