Incoloy 800H合金在模拟服役条件试验过程中的性能与组织演化研究

Properties and microstructure evolution of Incoloy 800H during simulated service condition test

利用模拟试验台对Incoloy 800H合金传热管在温度675℃、管内7 MPa高压蒸汽、管外微正压氦气保护环境下进行了20000 h的试验,研究了微观组织演化及力学性能变化规律。结果表明:试验后Incoloy 800H合金具有良好拉伸性能,室温拉伸性能均满足《蒸汽发生器用Incoloy 800H管材技术要求》对新管的要求;且随试验时间的延长,抗拉强度、规定塑性延伸强度和维氏硬度均呈先上升后稳定的趋势,老化20000 h后,3项指标较供货态分别上升了13.6%、7.9%和17.7%;析出相为晶界、晶内的M_(23)C_(6)型碳化物和晶内的二次Ti(C,N)相,且随着试验时间的延长,晶界不连续颗粒状M_(23)C_(6)碳化物尺寸增大;晶内弥散分布的M_(23)C_(6)和二次Ti(C,N),在5000 h之前其尺寸随服役时间延长而增大,5000 h时M_(23)C_(6)和二次Ti(C,N)的尺寸分别为230~320 nm和350 nm,之后两者尺寸基本稳定,未发现σ相和G相等有害相。Incoloy 800H合金的抗蒸汽氧化性能较好,氧化皮剥落风险较小。

The Incoloy 800H alloy heat transfer tube was tested for 20000 h at 675℃on simulation test bench in environment with 7 MPa high pressure steam inside the tube and micro positive pressure helium gas protection outside the tube.The microstructure evolution and mechanical property change were studied.The results showed that,the tensile properties of Incoloy 800H were excellent after test,which could meet the requirements of Technical Requirements of Incoloy 800H Tube for Steam Generator for new tubes.With the extension of test time,the tensile strength,specified plastic elongation strength and micro-Vickers hardness increased at first and then kept stable.After test for 20000 h,the three parameters increased by 13.6%,7.9%and 17.7%respectively.The M_(23)C_(6) carbides were mainly distributed along the grain boundaries and in the matrix,the second Ti(C,N)phases distributed in the matrix after test.The size of grain boundaries M_(23)C_(6) carbides increased slightly with the extension of test time.The size of M_(23)C_(6) carbides and secondary Ti(C,N)dispersed in the matrix increased with the extension of service time before test for 5000 h.After test for 5000 h,the sizes of M_(23)C_(6) carbides and secondary Ti(C,N)were 230~320 nm and 350 nm respectively,and then they were basically stable.No harmful phase like theσphase and G phase was found.Incoloy 800H alloy has good resistance to steam oxidation and low risk of spalling.