固溶处理对电子束熔炼镍基740合金组织与硬度的影响

Effect of solution treatment on microstructure and hardness of electron beam smelting Inconel 740 superalloy

利用电子束熔炼技术制备了镍基740高温合金,用扫描电镜、透射电镜、X射线衍射仪和维氏硬度计对740合金显微组织与硬度进行了表征,研究了固溶温度与时间对740合金显微组织与硬度的影响。结果表明,当固溶温度低于1210℃时,随着固溶温度的增加,TiNiSi相逐渐固溶到基体中。在1210℃进行固溶,随着固溶时间的增加,基体中一次MC碳化物尺寸减小。当固溶温度为1220℃时,长时间的固溶处理导致M_(23)C_6碳化物的分解,时效后晶界的G相由筏化的γ'相转变而来。1210℃与1220℃固溶处理2 h后时效处理得到的二次相平均尺寸均小于30 nm,其体积分数均为40%左右。在1230℃固溶将会导致固溶微孔的形成。740合金的维氏硬度值随固溶时间的增加变化不大,时效后合金的硬度显著增加,其值由位错之间以及位错与二次相的相互作用决定。

The Inconel 740 superalloy was prepared by electron beam melting technology,microstructure and hardness of the alloys were characterized by means of scanning electron microscopy,transmission electron microscopy,X-ray diffractometer and Vickers hardness tester,the effect of solution temperature and time on the microstructure and hardness of the 740 alloy was studied. The results show that when the solution temperature is lower than 1210 ℃,Ti Ni Si phase is soluted into the matrix gradually with increasing of solution temperature. When solution treated at 1210 ℃,the size of primary MC carbides in the matrix decreases with increasing of solution time. When the solution temperature is 1220 ℃,the decomposition of M23C6 is caused due to long time solution treatment,G phase on the grain boundaries is transformed from the rafting γ＇ phase after aging. The average size of secondary phase is less than 30 nm after solution treatment at 1210 ℃and 1220 ℃ for 2 h and aging,its volume fraction is 40% approximately. The solution microvoids will be formed when solution treated at1230 ℃. The Vickers hardness value show little change with increasing of solution time,the hardness of the alloy increases significantly after aging treatment,whose value is decided by the interaction between dislocations and dislocations with secondary phase.