High temperature stability of Cr-carbides in an experimental Co–Re-based alloy
High temperature stability of Cr-carbides in an experimental Co–Re-based alloy
复制标题
实验性钴铼基合金中铬碳化物的高温稳定性
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
J. Rösler
中科院分区：
文献类型：
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作者：
D. Mukherji;M. Klauke;P. Strunz;I. Zizak;G. Schumacher;A. Wiedenmann;J. Rösler
摘要研究了一种实验用钴铼基合金的高温组织稳定性。实验合金主要由铬碳化物强化，特别是由薄层板形式的碳化物强化。在1000和1200 °C下暴露1000 h的试样的电子显微镜研究表明，在这些温度下，以不同形态存在于合金中的Cr23 C6型碳化物是不稳定的。还观察到，在将样品暴露于升高的温度后，合金硬度下降，并且这种损失大部分发生在前100 h内。同步辐射原位衍射结果表明，在1 000 °C保温3 h后，碳化物开始溶解。此外，原位小角中子散射结果表明，在晶界处的碳化物和块状碳化物溶解，然后薄的层状碳化物。此外，由于Cr碳化物的溶解而发生的Cr在Co基体相中的富集稳定了富Cr-Re的σ相。虽然层状碳化物的溶解导致强度的显著损失，但具有极高硬度的σ相的形成部分地补偿了损失。σ相在1200 °C时仍保持稳定。
Abstract The stability of the microstructure at high temperatures was studied in an experimental Co–Re-based alloy. The experimental alloy is mainly strengthened by Cr-carbides, particularly by those in the form of thin lamellar plates. Electron microscopic investigation on samples exposed for up to 1 000 h to temperatures of 1 000 and 1 200 °C showed that Cr23C6 type carbides present in the alloy in different morphologies are unstable at these temperatures. It was also observed that the alloy hardness dropped after exposing the samples to elevated temperatures and much of this loss occurred within the first 100 h. In-situ diffraction measurements with synchrotron radiation showed that carbide dissolution started as early as 3 h of holding at 1 000 °C. Moreover, in-situ small angle neutron scattering results indicated that the carbides at the grain boundaries and the blocky carbides dissolve first and then the thin lamellar carbides. Further, the enrichment of Cr in the Co-matrix phase, which took place due to the dissolution of Cr-carbides, stabilized a Cr–Re-rich σ phase. Although the dissolution of lamellar carbides results in a significant loss of strength, the formation of σ phase with extremely high hardness partly compensated the for loss. The σ phase is stable even at 1 200 °C.