C1023镍基高温合金中时效析出σ相

研究了5种成分的C1023镍基高温合金850 ℃时效试样中析出σ相的形态、数量、分布及其对高温持久寿命的影响.对C1023合金铸态试样进行了850 ℃保温500 h的时效热处理及850 ℃、应力325 MPa的高温持久性能测试;对时效试样显微组织和持久试样断口形貌及微区成分进行观察分析,测定了时效试样中σ相的含量.结果表明,C1023合金850 ℃时效析出的σ相有2种典型形态:在枝晶间均匀分布的颗粒以及从枝晶间伸向枝晶干的长针;在850 ℃时效240 h左右出现析出峰,时效400 h之后σ相的生成量相对稳定.存在合金成分-σ相生成量-高温持久寿命之间的良好对应关系.成分中Cr、Mo等元素含量在成分范围的下限,而C与Ti含量在成分范围中限的合金,时效σ相的生成量相对少,σ针相对短粗,对应具有相对最高的持久寿命.

Aging precipitated σ phase in Ni-based superalloys C1023

Morphology,content and distribution characteristics of σ phase precipitated from aging specimens in 5 kind of Ni-based superalloys C1023 and its effects on endurance at high temperature were studied.Aging heat treatment at 850 ℃ for 500 h and endurance test at 850 ℃ and stress 325 MPa of as-cast superalloy C1023 samples were conducted.The microstructure and endurance fracture morphology of samples after aging were observed with SEM.The σ phase content was measured.The results show that there are 2 typical morphologies of aging σ phase.They are particles(Ti,Mo)C in dendrite grains and needles of(Cr,Mo)23C 6 along dendrite boundaries.The precipitating peak of the σ phase at 850 ℃ is about 240 h.Then the precipitating amout of the σ phase is relative stable.There is the definite corresponding relationship among σ phase content,alloy composition and endurance at high temperature.The alloys containing lower amount Cr,Mo and medium amount C,Ti have minimum σ phase with short needle and have comparatively the highest endurance correspondingly.