Transactions of Nonferrous Metals Society of China The Chinese Journal of Nonferrous Metals

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中国有色金属学报

ZHONGGUO YOUSEJINSHU XUEBAO

第29卷    第5期    总第242期    2019年5月

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文章编号:1004-0609(2019)-05-0983-07
IN718镍基高温合金的热机械疲劳性能
邓文凯1, 2,徐睛昊1, 2,江 亮1, 2

(1. 中南大学 粉末冶金国家重点实验室,长沙 410083;
2. 中南大学 粉末冶金研究院,长沙 410083
)

摘 要: 对IN718镍基高温合金进行温度循环为350~650 ℃及不同应变幅条件下的同相(IP)和反相(OP)热机械疲劳试验;比较同相和反相的热机械疲劳循环应力响应行为、滞后回线以及疲劳寿命;运用金相显微镜、扫描电子显微镜对材料的微观结构以及断口特征进行分析。结果表明:IN718合金的热机械疲劳应力-应变滞后回线最大拉应力与压应力不对称,表明合金在350~650 ℃范围内高温时抵抗变形阻力较小;合金的循环应力响应行为在低应变幅的同相热机械疲劳的高温半周呈现循环硬化现象,其余情况均为循环软化现象;合金的同相热机械疲劳寿命明显低于反相热机械疲劳寿命,合金热机械疲劳寿命在应变幅超过0.6%的条件下符合Coffin-Manson方程,在应变幅0.4%的情况下实际疲劳寿命值偏高;IN718合金的同相热机械疲劳的疲劳源处断口为沿晶断裂,反相热机械疲劳的为穿晶断裂,裂纹扩展区和瞬断区均为韧窝断裂。

 

关键字: IN718镍基高温合金;热机械疲劳;同相;反相;疲劳寿命;断口

Thermo-mechanical fatigue behavior of Inconel 718 superalloy
DENG Wen-kai1, 2, XU Jing-hao1, 2, JIANG Liang1, 2

1. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China;
2. Powder Metallurgy Research Institute, Central South University, Changsha 410083, China

Abstract:This research focuses on the thermomechanical fatigue (TMF) performance of IN718 superalloy upon in-phase (IP) and out-of-phase (OP) loading modes, respectively. The differences of strain response, hysteresis loop and fatigue life between IP and OP were compared. The hysteresis loop curves show that the stresses are not symmetric during tension and compression loading, and exhibiting relatively low deformation resistance at high temperature. In most cases, the stress exhibits cyclic softening behavior, only while at the IP TMF fatigue and upon low strain amplitude, the stress displays cyclic hardening behavior in the high temperature half cycles. The S-N curves show that the fatigue life upon out-of-phase mode exceeds that of in-phase process. The S-N plots are in accordance with the Coffin-Manson formula for the strain range over 0.6%, while it is not true below strain range of 0.4%. The microscopic examination shows that intergranular fracture dominates the deformation process for the in-phase TMF, which is contrast with the intragranular fracture for the out-of-phase counterparts. The dimples can be ubiquitously observed for these two fatigue modes.

 

Key words: IN718 superalloy; thermomechanical fatigue; in-phase; out-of-phase; fatigue life; fracture

ISSN 1004-0609
CN 43-1238/TG
CODEN: ZYJXFK

ISSN 1003-6326
CN 43-1239/TG
CODEN: TNMCEW

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