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通过热力学模拟软件Thermo-calc优化合金成分,结合实验研究,开发了一种在750℃环境中工作的新型镍基气阀合金LF8。计算结果表明:随Cr含量增加,γ’相稍有增加,碳化物由M_7C_3转变为M_(23)C_6;Ti含量超过4.5%时合金中有大量η相生成。实验研究结果表明:合金热处理后的主要析出相为γ’、Cr_(23)C_6和TiC,γ’相呈近球形,细小弥散分布在晶内,尺寸为20 nm;Cr_(23)C_6大部分在晶界处不连续分布,呈椭圆或者点状,尺寸为400~800 nm;TiC在晶内或者晶界附近呈块状分布,以初生TiC为主。通过优化合金成分开发的LF8气阀合金室温和高温强度以及硬度均高于Nimonic 80A,有希望成为750℃气阀合金的备选材料。
Through the optimization of the alloy composition by thermo-simulation software Thermo-calc, a new nickel base valve alloy LF8 working at 750 ℃ has been developed in combination with experimental research. The calculated results show that as the content of Cr increases, the γ ’phase increases slightly and the carbide changes from M_7C_3 to M_ (23) C_6. When Ti content exceeds 4.5%, a large amount of η phase is formed in the alloy. The experimental results show that the main precipitates are γ ’, Cr_ (23) C_6 and TiC after heat treatment, and the γ’ phase is nearly spherical with small and diffuse distribution in the crystal with a size of 20 nm. Most of Cr_ (23) C_6 Discontinuous distribution in the grain boundaries, oval or dot-shaped, the size of 400 ~ 800 nm; TiC in the grain or grain boundaries were block-like distribution to the primary TiC-based. Developed by optimizing the composition of LF8 valve alloy valve alloy room temperature and high temperature strength and hardness are higher than the Nimonic 80A, hope to become 750 ℃ valve alloy alternative materials.