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将18Cr10NiNb耐热钢在650℃进行10,000h的时效试验,用扫描电镜和透射电镜分析了18Cr10NiNb奥氏体耐热钢的组织,通过热力学计算研究了500-1400℃碳、铌和氮含量的变化对平衡析出相的影响。结果表明:在18Cr10NiNb钢的时效过程中在晶内析出了富Nb的MX相,在晶界析出了富Cr的M_(23)C_6相。根据热力学计算,其平衡析出相为MX,M_(23)C_6和σ相。MX相和M_(23)C_6型碳化物的最高溶解温度分别约为1340℃和840℃。MX相的数量随C和Nb含量的提高而增加。σ相的数量随着C含量的提高而减少。添加0.2%的N元素后,MX相为含有N、Nb、Cr和少量C的复杂碳氮化物,且在其平衡组织中出现了Cr_2N相。
The 18Cr10NiNb heat-resistant steel was subjected to aging test at 650 ℃ for 10,000h. The microstructure of 18Cr10NiNb austenitic heat-resistant steel was analyzed by scanning electron microscopy and transmission electron microscopy. The changes of carbon, niobium and nitrogen contents at 500-1400 ℃ were studied by thermodynamic calculation On the balance of precipitation. The results show that during the aging process of 18Cr10NiNb steel, the Nb-rich MX phase precipitates and the Cr-rich M_ (23) C_6 phase precipitates in the grain boundary. According to thermodynamic calculation, the equilibrium precipitates are MX, M_ (23) C_6 and σ phase. The highest melting temperature of MX phase and M_ (23) C_6 type carbides are about 1340 ℃ and 840 ℃, respectively. The amount of MX phase increases with the increase of C and Nb contents. The amount of σ phase decreases with increasing C content. After adding 0.2% N element, the MX phase is a complex carbonitride containing N, Nb, Cr and a small amount of C, and the Cr 2 N phase appears in its equilibrium structure.