18Cr-9Ni-3Cu钢长期服役后的组织与力学性能

Microstructure and mechanical properties of 18Cr-9Ni-3Cu steel after long-term service

利用力学性能试验机、光学显微镜、扫描电镜、能谱检测和透射电镜研究了18Cr-9Ni-3Cu钢在超超临界机组服役5×104h后的微观组织和力学性能。结果表明:服役后18Cr-9Ni-3Cu钢主要析出物为M23C6相、σ相、Nb(C,N)相及富Cu相,其中M23C6及σ相在晶界呈链状析出,Nb(C,N)在晶内聚集。第二相析出强化及M23C6共格强化是18Cr-9Ni-3Cu钢强度增加的主要原因,而σ相的大量析出导致材料塑性及冲击性能降低。此外,服役态向火侧较背火侧析出物尺寸大且析出量多,强度增量较大,塑性和冲击性能下降较多。

Mechanical properties test,optical microscopy,scanning electron microscopy and transmission electron microscopy were used to study microstructure and mechanical properties of 18 Cr-9 Ni-3 Cu steel after serving in a power plant for 5 × 104 h. The results show that M23 C6,σ phase,Nb（ C,N） and Cu-rich particle are the main precipitates in 18 Cr-9 Ni-3 Cu steel after serving. Amounts of continuous M23 C6 and σphase precipitate along grain boundary in a chain-like manner,coarse Nb（ C,N） precipitates inside austenite grains. σ phase leads to the decreases of plasticity and impact properties. Second-phase precipitation strength and coherent strength are the main reason of tensile strength increasing. Additionally,compared with the leeward,the windward in service mode has more precipitates and bigger size,greater strength increment,and more decreases of plasticity and impact properties.