镍基单晶合金中TCP相的析出行为及其对持久性能的影响

Precipitation behavior of TCP phase and its influence on stress rupture property of single crystal nickel-based superalloys

通过对有/无元素Re、有/无TCP相合金进行时效处理、持久性能测试及组织形貌观察,研究TCP相的析出特征以及元素Re、TCP相对合金持久寿命的影响。结果表明:在时效期间,合金中析出的TCP相在{111}晶面沿<110>晶向呈片状析出,其在(100)晶面具有相互平行或垂直的针状形貌,在(111)晶面呈现互成60°角排列的针状形貌,该TCP相鉴定为μ相。在无Re合金中析出的μ相尺寸较小,在时效期间不发生球化;而在4.5%Re合金中析出的μ相尺寸较大,且随时效时间的延长,μ相逐渐粗化并转变成球状。由于析出的μ相消耗较多的难溶元素,故可明显降低合金的蠕变抗力和缩短持久寿命。其中,无Re合金2中析出的针状μ相,在蠕变期间易产生应力集中,并促使其发生裂纹萌生和扩展,是较大幅度缩短合金持久寿命的主要原因;在4.5%Re合金中形成的球状μ相,在蠕变期间不易产生应力集中,是使合金持久寿命缩短幅度减小的主要原因。

By means of measurement of the stress rupture property and microstructure observation,an investigation was made on the features of TCP phase precipitated and the influence of element Re and TCP phase on the stress rupture property of the single crystal nickel-based superalloys.The results show that during aging,TCP phase is precipitated along the 110 orientation on {111} planes in the form of the slice-like structure.Thereinto,TCP phase displays a strip-like morphology,arranging in the upright each other on the {100} planes,or arranging at an angle of 60° each other on the {111} planes,and the TCP phase is identified as μ phase.The μ phase precipitated in the free-Re alloy is shorter in size,and no feature of the spheroidization is detected during the aging.But the μ phase precipitated in the 4.5%Re alloy displays a longer size,and the coarsening occurs as the aged time prolongs,and then μ phase is gradually transformed into the sphere-like morphology.The precipitated TCP phase may obvious decrease the creep resistance and stress rupture lifetimes of the superalloys due to the consumption of the refractory elements.Thereinto,the stress concentration is easily generated in the regions near the strip-like μ phase in the free-Re alloy,and promotes the initiation and propagation of the cracks during creeping,which is a maim reason reducing the stress rupture lifetimes of the alloy a great extent.And the stress concentration is not easily generated in the regions near the sphere-like μ phase in 4.5% Re alloy,which is a main reason reducing the stress rupture lifetimes of the alloy a small extent.