【作者】 杨旭；

【导师】 刘江南；

【作者基本信息】 西安工业大学 ， 材料学， 2012， 硕士

【摘要】 00Cr18Ni10N奥氏体不锈钢是在不含氮的18-8型不锈钢基础上发展起来的新钢种,因其具有高强度和高韧性以及耐蚀性优良等特点,在航空领域广泛用于制造飞机的液压系统导管、卡箍、壳体、螺母和角盒等构件。由于这些构件在服役时受到高温和交变载荷的作用,长时间运行后容易发生突然断裂,严重影响了飞机的飞行安全。因此,很有必要对00Cr18Ni10N钢的高温持久性能和疲劳性能进行详细的研究。本文采用高温拉伸试验、高温持久强度试验和疲劳裂纹扩展试验对00Cr18Ni10N钢的高温持久性能和疲劳性能进行了研究,并在扫描电镜下对高温瞬时拉伸试样、高温持久强度试样和CT试样的断口形貌进行观察。研究结果表明：在Larson-Miller方程基础上所建立的00Cr18Ni10N钢高温抗拉强度与持久强度之间数学模型,可以很好地预测其持久强度,预测值和实测值之间的最大相对误差小于4.3%。通过高温持久强度试验分别测定了00Cr18Ni10N钢在550℃,600℃和700℃下的持久强度σ100、σ200和σ500。结果表明：在同一温度下,持久时间越长,持久强度越低：在同一持久时削下,试验温度越高,持久强度越低。不同应力比下00Cr18Ni10N钢疲劳裂纹扩展性能研究结果显示：应力幅度越小,疲劳裂纹扩展速率越慢。SEM断口分析表明：高温瞬时拉伸试样宏观断口有明显的纤维区,放射区和剪切唇；微观断口可观察到大量的韧窝、孔洞及第二相粒子,属于微孔聚集型韧性断裂。高温持久强度试样的宏观断口表面比较粗糙,低倍照片呈现出冰糖状；微观断口可见典型的楔形裂纹,晶界空洞是该材料断裂的主要原因。疲劳断口的微观形貌呈现准解理断裂特征,裂纹扩展区主要以疲劳条带扩展机制为主。应力幅度越大,疲劳条带越宽；应力幅度越小,疲劳条带相对密集。在瞬时破断区可以看到二次裂纹和大量的韧窝以及撕裂棱。更多还原

【Abstract】 OOCr18NilON steel is the new kind of steel which has been developed on 18-8 nickelless stainless steel. Because of the good property of high strength, high toughness and corrosion resistance, it has been widely used in the aircraft industry for the airplane parts, such as the hydraulic system catheters, clamps, shells, nuts, angle boxes and etc. For suffering from high temperatures and alternating load in the flight, these components will unpredictably break after long term service and seriously threaten the aircraft’s safety. Therefore, it is very necessary to study its high-temperature enduring properties and fatigue performance.In this paper, the enduring properties and fatigue performance of 00Cr18Ni10N steel have been studied by high-temperature tensile test, high-temperature enduring test and fatigue crack growth rate test and the fracture morphology of the samples has been observed by scanning electron microscope. The main results are as follows.Based on the Larson-miller parameter equation, the mathematical model in the given temperature of 00Cr18Ni10N steel is established with the relationship between the enduring strength and the high temperature tensile strength. The enduring strength can be accurately predicted by the high-temperature tensile strength, and the maximum relative error between the predicted value and the measured value is less than 4.3%.Theσ100,σ200, andσ500 enduring strength at 550℃,600℃and 700℃of 00Cr18Ni10N steel was measured and the results indicated that under the same temperature, the enduring strength decreases with the increasing of the enduring time and for a given enduring time there is the same variation tendency for the enduring strength with the test temperature.The results of fatigue crack propagation rate test show that the fatigue crack growth rate decreases with the decreasing of the stress ratio.SEM fracture analysis shows that the macro-fracture surface of the high temperature tensile has the obvious fibrous zone, radical zone and shears lips. Micro-fracture observation reveals that thers are a large number of dimples, holes and the second phase particles in the fracture and its fracture mechanism belongs to ductile fracture with microvoid aggregation. The macro-fracture surface of enduring samples looks very rough and appears the rock candy shape. The typical wedge-shaped cracks and the grain boundary voids have been observed in the micro-fracture and it reveals that the the grain boundary void is the main reason for the enduring fracture of 00Cr18Ni10N steel. Fatigue fracture morphology showed the characteristics of quasi-cleavage fracture. Fatigue mode in crack propagation region was mainly strip propagation mechanism and the width of the fatigue stripe increases with the increasing of the stress ratio. Moreover, secondary cracks, a number of shallow dimples and some lacerate ribs are observed in the instantaneous breaking zone.更多还原