摘要
Precipitation behavior of P550 steel for non-magnetic drill collars was investigated by microstructure characterization as well as thermodynamic calculation.The results demonstrate that the main precipitate formed at 650–900℃was cellular Cr_(2)N,and its precipitation depended heavily on the aging temperature.The most sensitive precipitation temperature of cellular Cr_(2)N was 750℃.At 750℃,the cellular Cr_(2)N exhibited fast-slow precipitation kinetics with the aging time prolonging.The initial precipitation of cellular Cr_(2)N was governed by the short-range intergranular diffusion of Cr.During long-term aging,its growth was controlled by the long-range bulk diffusion of Cr.In addition,cellular Cr_(2)N induced the precipitation of r phase ahead of the cell after long period of aging.Increasing the nitrogen content resulted in the increment of both the nucleation site and the driving force for the cellular Cr_(2)N,which jointly promoted its precipitation.
基金
the National Natural Science Foundation of China(Grant Nos.U1960203 and 51774074)
Shanxi Municipal Major Science&Technology Project(Grant No.20181101014)
Fundamental Research Funds for the Central Universities(Grant Nos.N172512033 and N2024005-4)
Talent Project of Revitalizing Liaoning(XLYC1902046)
State Key Laboratory of Metal Material for Marine Equipment and Application(Grant No.HG-SKL(2019)13).
