超超临界锅炉用新型奥氏体耐热钢HR3C的高温时效脆化研究
Study on Aging Embrittlement of New Type Austenitic Heat Resistant Steel HR3C Used in USC Boiler
李太江, 刘福广, 范长信, 姚兵印
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作者单位：(西安热工研究院有限公司, 陕西 西安 710032)
中文关键字：超超临界机组； 奥氏体耐热钢； HR3C； 时效脆化
英文关键字：USC boiler; austenitic heat resistant steel; HR3C; aging embrittlement
中文摘要：通过冲击性能试验、 光镜、 透射电镜和扫描电镜等方法对超超临界机组用新型奥氏体耐热钢HR3C经650 ℃时效不同时间后的冲击韧度和显微组织变化进行了研究。 结果表明，HR3C钢在650 ℃时效过程中具有较明显的时效脆化倾向，时效500 h后冲击韧度由时效前的351.7 J/cm2降低到40 J/cm2以下，而后随着时效时间的延长(直至6000 h)，冲击韧度基本稳定在20～25 J/cm2；HR3C钢长时时效后的断裂形式主要是以沿晶断裂为主的脆性断裂；时效初期HR3C钢冲击韧度降低的主要原因是由于沿晶析出较多网状M23C6和少量σ沉淀相造成的；时效后期，M23C6出现聚集、球化、长大，但由于σ相的析出量增加，使该钢时效6000 h后 的冲击韧度仍保持在较低的水平。
英文摘要：The impact toughness and microstructure variation of new type austenitic heat resistant steel HR3C used in USC boilers aging at 650 ℃ for different time were studied through impact property test, OM, TEM and SEM. The results show that the aging embrittlement of HR3C steel is obvious, the impact toughness decreases to below 40 J/cm2 after aging at 650 ℃ for 500 h from 351.7 J/cm2 before aging treatment and with the continuation of aging time, the impact toughness changes between 20 J/cm2 and 25 J/cm2. The fractography of impact specimen is intergranular brittle fracture. The microstructure results indicate that the main reasons for the impact toughness degradation are the dispersion of net-like M23C6 and a little amount of σ phase along grain boundary at early stage, at later stage, the combination of M23C6's spheroidizing, congregation and coarsening and the amount of σ phase increasing is responsible for the embrittlement of HR3C steel.