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以新型1900 MPa级超高强度马氏体时效不锈钢为研究对象,通过激光扫描共聚焦显微镜对其超声疲劳试样断口进行观察与分析。结果表明,在超声疲劳试验过程中,所有的试样在表面均产生了烧蚀的痕迹。对于表面起裂的超声疲劳试样,即使在不同的应力幅值下(640~560 MPa),试样的疲劳寿命均在105周次左右,且烧蚀现象更为严重。而对于基体内起裂的试样,烧蚀现象较为轻微,且烧蚀处均在断口两侧几乎对称的位置。经对比分析可知,超声疲劳过程中产生的热效应对表面起裂试样的疲劳寿命有很大的影响,而内部起裂试样的疲劳寿命对超声疲劳热效应不敏感。
A new type of 1900 MPa ultrahigh strength martensitic stainless steel was taken as the research object. The fracture of ultrasonic fatigue specimen was observed and analyzed by laser scanning confocal microscope. The results show that during the ultrasonic fatigue test, all the samples have ablated traces on the surface. For ultrasonic fatigue specimens with surface cracking, the fatigue life of the specimens is about 105 weeks even at different stress amplitudes (640-560 MPa), and the ablation phenomenon is more serious. For the samples with rupture in the matrix, the ablation phenomenon is slight, and the ablation sites are almost symmetrical on both sides of the fracture. The comparative analysis shows that the thermal effect produced by the ultrasonic fatigue has a great influence on the fatigue life of the surface cracking specimen, while the fatigue life of the internal cracking specimen is not sensitive to the ultrasonic fatigue thermal effect.