P92钢时效的Laves相演化行为  

LAVES PHASE EVOLUTION IN P92 STEEL DURING AGEING

作　　者：王学[1,2] 于淑敏[1] 任遥遥[1] 刘洪 刘洪伟 胡磊[1,2] 

机构地区：[1]武汉大学动力与机械学院,武汉430072 [2]武汉大学流体机械与动力工程装备技术湖北省重点实验室,武汉430072 [3]东方电气集团东方锅炉股份有限公司,自贡643001

出　　处：《金属学报》2014年第10期1195-1202,共8页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目51074113和51374153;四川省应用基础研究计划项目2013JY0123资助~~

摘　　要：对P92钢进行650℃,0~8000h时效实验,采用SEM-BSE和定量金相技术对Laves相的体积分数、平均直径和数量密度进行定量,研究了Laves相的析出和粗化动力学特性,评估了Laves相演化对蠕变强度的影响.结果表明,Laves相在时效0~2000 h内析出,优先在晶界析出长大,最终析出时的体积分数约为0.95%.Laves相粒子在时效3000 h后明显聚集粗化,粗化速率明显快于M23C6碳化物的原因是由于晶界扩散机制的作用.Laves相在1000~3000 h内具有最佳的析出强化效果,超过3000 h后由于显著粗化使沉淀强化作用明显下降.由于体积分数小和热稳定性差,Laves相的强化作用远小于M23C6型碳化物.ASME P92（9Cr-0.5Mo-1.8WVNb） is a key material for the main steam pipe and header with larger diameter and thick wall in ultra-supercritical（USC） plant,because of its low thermal expansion coefficient,good corrosion resistance,good fabricability and especially its high creep rupture strength.The Laves phase（Fe2M） precipitates in service and plays complicated and controversial role in affecting and/or determining the creep strength of the P92 steel.The fine Laves phase particles may contribute to precipitation strengthening and decrease the creep rate in the primary and transient creep region,however,the subsequent coarsening of Laves phase reduces the precipitation strengthening.Thus,in order to provide a systematic and definite understanding of the creep properties,it is necessary to investigate the precipitation and coarsening behavior of the Laves phase in P92 steel.In this work,the Laves phase parameters of P92 steel,including volume fraction,mean diameter and number density,were measured using SEM-BSE and quantitative metallography methods during aging at 650 ℃ for 0~8000 h.The precipitate and coarsening kinetics were investigated based on the quantification of Laves phase in P92 steel.Furthermore,the martensitic lath stability during aging was observed by OM and TEM.Lastly,the influence of Laves phase evolution on the creep rupture strength was estimated from the change of Orowan stress during aging.The results indicate that SEM-BSE is a suitable method for measurement of Laves phase precipitates,and can achieve significantly statistical data when characterizing large particles comparing with the EFTEM,so that evaluate the kinetics of precipitation and coarsening of Laves phase.The Laves phase precipitates at grain boundaries preferentially during the 0~2000 h of aging and its final volume fraction is around 0.95%.Obvious coarsening of Laves phase is observed after aging for 3000 h and its rate is much greater than that of M23C6 carbides.Grain boundary diffusion may play significant role in muc

关 键 词：P92钢 LAVES相 析出 粗化 蠕变强度 

分 类 号：TG142.7[一般工业技术—材料科学与工程]