不锈钢复合板热疲劳性能分析

利用冷热疲劳试验机模拟分析了冷热循环对不锈钢复合板热疲劳性能的影响,并采用扫描电镜、电子探针和电子背散射衍射仪对热疲劳试样V形缺口及裂纹区域的形貌和成分进行了深入分析。结果表明,不锈钢复合板热疲劳试样经 20~550 ℃ 7 500次冷热循环后,结合界面处V形缺口区出现微裂纹,且微裂纹起裂于V形缺口尖端基层侧。随着冷热循环的继续进行,微裂纹向基层内扩展,但并非沿着结合界面处扩展,而是沿着基层侧扩展。此外,热疲劳裂纹的起裂和扩展与氧化和应力作用有关,微裂纹起裂于热疲劳试样 V 形缺口区域基层侧表层局部氧化孔洞,并在冷热循环的应力作用下向基层内扩展,同时加剧氧化。随着冷热循环的继续进行,晶界氧化逐渐加剧,导致微裂纹扩展成更为明显的裂纹。

Analysis on thermal fatigue properties of stainless steel clad plate

The effects of cooling and heating cycles on the thermal fatigue properties of stainless steel clad plate were simulated by hot and cold fatigue testing machine, and the morphology and composition of V-notch and crack area for thermal fatigue sample were analyzed by scanning electron microscope(SEM), electron probe microanalyzer(EPMA) and electron back-scattered diffraction(EBSD). The results show that microcracks appeare in the V-notch region at the bonding interface of thermal fatigue sample of stainless steel clad plate after 7 500 cooling and heating cycles at 20-550 ℃, and the microcracks originate from the base side of V-notch tip. As the cycle of heating and codling continues, the microcracks expand into the base steel along the base side, but not along the interface. In addition, the initiation and propagation of thermal fatigue cracks are related to oxidation and stress, and the microcracks start from the local oxidation holes on the surface of base layer in V-notch region of thermal fatigue sample, and expand into the base layer under the action of hot and cold cyclic stress, the oxidation is accelerated at the same time. As the cooling and heating cycles continuing, grain boundary oxidation is gradually intensified, resulting in the microcracks expensing into more obvious cracks.