Effect of cooling rate on microstructure and tensile properties of powder metallurgy Ni-based superalloy  

冷速对一种镍基粉末高温合金的显微组织和拉伸性能的影响（英文）

作　　者：Han-hui DING Guo-ai HE Xin WANG Feng LIU Lan HUANG Liang JIANG 丁晗晖;何国爱;王薪;刘锋;黄岚;江亮(中南大学粉末冶金国家重点实验室,长沙410083;中南大学粉末冶金研究院,长沙410083)

机构地区：[1]State Key Laboratory of Powder Metallurgy,Central South University,Changsha 410083,China [2]Powder Metallurgy Research Institute,Central South University,Changsha 410083,China

出　　处：《Transactions of Nonferrous Metals Society of China》2018年第3期451-460,共10页中国有色金属学报（英文版）

基　　金：Project(2012AA03A514)supported by the National High-Tech Research and Development Program of China;Projects(2016YFB0700300,2016YFB0701404)supported by the National Key Research and Development Program of China

摘　　要：The effects of size distribution,morphology and volume fraction ofγ′phase and grain size on tensile properties of powder processed Ni-based superalloy were investigated by using two different quenching methods.Oil quenching and air cooling were adopted with cooling rate of 183°C/s and 4?15°C/s,respectively.The experimental results show that the average size of the secondaryγ′after oil quenching is 24.5 nm compared with 49.8 nm under air cooling,and corresponding volume fractions ofγ′are 29%and 34%,respectively.Meanwhile,the average grain size remains nearly equivalent from both oil-quenching and air-cooling specimens.The tensile strength at room temperature is higher for the oil-quenched specimen than the equivalent from the air-cooled specimen,but the difference approaches each other as the temperature increases to 650°C.The fractography clearly demonstrates that transgranular fracture governs the failure process at ambient temperature,in contrast to the intergranular fracture at 650°C or even higher temperature.These two mechanical responses indicate the strengthening effects ofγ′precipitates and grain boundary for polycrystalline Ni-based superalloys at different temperatures.研究不同淬火制度下晶粒尺寸及强化相γ′的尺寸分布、形貌和体积分数对镍基高温合金拉伸性能的影响。采用油淬和空冷两种淬火方式,其对应的平均冷却速度分别为183°C/s和4~15°C/s。实验结果表明,油淬和空冷后的二次γ′相的平均尺寸分别为24.5 nm和49.8 nm,相应的体积分数分别为29%和34%;然而两种条件下的平均晶粒尺寸几乎相等。在室温下,油冷态γ′相的拉伸强度高于空冷态的,当温度升高到650°C时,二者强度逐渐接近。断口形貌分析表明,在室温下,断口由穿晶断裂主导;随着温度升高,直至650°C以上,断口由沿晶断裂主导。结果表明,强化相γ′和晶界在镍基粉末高温合金中不同温度下发挥着不同的强化作用。

关 键 词：powder metallurgy Ni-based superalloy cooling rate tensile properties γ′phase precipitate fracture mechanism 

分 类 号：TG132.3[一般工业技术—材料科学与工程]