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采用透射电镜(TEM)、扫描电镜(SEM)对不同服役时间下的含Hf涡轮叶片典型部位的组织进行了观察与定量表征,采用能谱分析仪(EDS)对服役过程中的碳化物的成分变化进行了分析,并对不同服役时间叶片进行显微硬度测试,研究了含Hf涡轮叶片在服役过程中组织及性能的演化规律,并根据LSW理论对不同部位的服役温度进行了定量反推。结果表明:在高温高应力下,服役400,650 h的叶片均发生了明显的组织退化,作为主要强化相的γ’粒子由规则立方体形貌逐渐粗化长大为L,H型等较为复杂的粒子形态,其等效直径由0.53μm增大至0.64μm,粗化过程由Ostwald熟化机制与粒子聚集机制的共同控制;其中,叶身中部粗化现象最为严重,经反推,其服役温度可达1180K;碳化物由富Ti-Ta的MC(1)型转变为富Hf的MC(2)型,并析出少量M23C6型碳化物,Hf元素在一定程度上抑制了M6C及TCP相的析出;在晶内第二相与γ基体界面及筏排处出现少量蠕变空洞,即蠕变空洞在位错堆积前沿萌生;随着服役时间的延长,合金的显微硬度逐渐降低,发生明显软化。
The microstructure of typical Hf turbine blades with different service time was observed and characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The composition of carbide during service was analyzed by energy dispersive spectroscopy (EDS) The microstructure and properties of Hf turbine blades during service were studied. The LSW theory was used to quantitatively estimate the service temperature of different parts. The results showed that under the condition of high temperature and high stress, obvious leaf tissue degeneration took place in 400 and 650 h after inoculation. As the main strengthening phase, the γ ’particles gradually roughened from the regular cube shape to the more complicated particles such as L and H type Morphology, the equivalent diameter increased from 0.53μm to 0.64μm, roughening process by the Ostwald ripening mechanism and particle aggregation mechanism jointly controlled; of which, the middle of the leaf body roughening the most serious, by reverse thrust, its service temperature up to 1180K. Carbides changed from MC (1) rich in Ti-Ta to MC (2) rich in Hf, and a small amount of M23C6 carbides were precipitated. Hf elements inhibited the precipitation of M6C and TCP phases to a certain extent. A small amount of creep voids appear in the intergranular phase and γ matrix interface and in the raft row, that is, creep voids develop at the frontier of dislocation accumulation. With the extension of service time, the microhardness of the alloy gradually decreases and softens obviously.