高温时效对25Cr35Ni-Nb合金碳化物的影响

摘要

25Cr35Ni - Nb合金被广泛用作乙烯裂解炉和制氢转化炉炉管材料,服役温度高达1050℃.将25 Cr35 Ni - Nb合金炉管在不同温度时效100 h,通过对不同温度显微组织的观察和维氏硬度测试,研究了不同温度时效后碳化物的变化规律.研究结果表明:随着时效温度的升高,晶界碳化物宽度不断增大,由原始铸态平均宽度1.5 μm,增大到1200℃时效后的5.3 μm;从900℃到1100℃,奥氏体晶内碳化物平均尺寸由1 μm长大至2μm,然而,随着时效温度提高至1200℃,晶内碳化物平均尺寸下降至1.7 μm.当时效温度从900℃增加为1100℃时,维氏硬度从173 HV10升高为192 HV10,1200℃时,维氏硬度为193 HV10.碳化物尺寸及维氏硬度与时效温度之间定量关系对炉管服役温度范围的确定提供了参考.%25Cr35Ni - Nb alloys were widely used in ethylene pyrolysis and hydrogen generation reformer furnace tube materials, the wall temperature were usually up to 1050 ℃. The 25Cr35Ni - Nb alloys were heated for 100 hours at different temperatures. By observing the microstructure and testing vickers hardness of as -cast and aged 25Cr35Ni - Nb alloys, the carbide transformation characterization at different aging temperature was studied. The results indicated that with aging temperature increased, the width of intergranular carbides became larger, in as -cast tubes, the average width of intergranular carbides was about 1.5 μm, with the aging temperature raised to 1200 ℃ , the average width of intergranular carbides grown up to 5.3 μm. When the aging temperature raised from 900 ℃ to 1100 ℃ , the average size of in-tragranular carbides grown from 1.0 μm to 2.0 μm. However, with aging temperature up to 1200 ℃, the average size of intragranular carbides decreased to 1.7 μm. When the aging temperature raised from 900 ℃to 1100 ℃, the vickers hardness raised from 173 HV10 to 192 HV10, while aging temperature increased to 1200 ℃, the vickers hardness was 193 HV10 with little variety compared with aging at 1100 ℃. The quantitative relationship between size of carbides and vickers hardness with aging temperature provided a reference for confirmation of 25Cr35Ni - Nb alloy tube real serve temperature.