Ni-24Fe-14Cr-8Mo镍基合金锻造开裂原因探究

STUDY ON FORGING CRACKING OF Ni-BASE ALLOY Ni-24Fe-14Cr-8Mo

以Ni-24Fe-14Cr-8Mo合金为研究对象,采用电子探针、扫描电镜、能谱分析、X射线衍射等检测手段,研究了第二相的析出规律,以及对锻造开裂的影响作用。结果表明,Ni-24Fe-14Cr-8Mo合金锻态组织中除了纳米级Mo_(2)C、Nb_(2)C与TiC碳化物之外,晶界与晶内还存在大量1~5μm的富Nb、Mo球形Laves相;在合金锻造裂纹附近存在的析出相为球形Laves相与短棒状σ相,后者直接造成塞积位错应力集中导致开裂;短棒状σ相析出温度范围为850~950℃,且密度增长迅速,高于950℃则逐步回溶到基体中,1000℃基本观察不到σ相的析出;Laves相在800~1000℃时效过程基本没有发生形貌变化,析出相的数量也没有显著改变。通过将终锻温度提高至950℃以上,避免棒状σ相大量析出,可以有效改善Ni-24Fe-14Cr-8Mo合金锻造开裂问题。

Taking Ni-24Fe-14Cr-8Mo alloy as the research object,the precipitation law of the second phase and its effect on forging cracking were studied by means of electron probe microanalysis,scanning electron microscopy,energy spectrum analysis and X-ray diffraction.The results show that,in addition to Nano-sized Mo_(2)C,Nb_(2)C and TiC carbides,there are a large number of 1~5μm Nb-rich and Mo-rich Spherical Laves phases in the grain boundaries and grains of Ni-24Fe-14Cr-8Mo alloy.The precipitated phases near the forging crack are spherical Laves phase and short Rodσphase,the latter directly causes plug dislocation stress concentration and leads to crack,the precipitated temperature of Short Rodσphase is 850~950℃,and the density of the precipitated phase increases rapidly,above 950℃,σphase cannot be precipitated at 1000℃,and the morphology of Laves phase does not change and the number of precipitates does not change significantly at 800~1000℃.The forging cracking of Ni-24Fe-14Cr-8Mo alloy can be effectively improved by raising the final forging temperature above 950℃and avoiding large amount of Barσphase precipitation.