Co对NiCrMoV系海工钢组织与性能的影响  

Effect of Co on microstructure and mechanical properties of NiCrMoV marine steel

作　　者：刘浩[1,2] 李健[2] 王贞[1] 刘静[1] 罗小兵[2] 柴锋[2] LIU Hao;LI Jian;WANG Zhen;LIU Jing;LUO Xiaobing;CHAI Feng(The Laboratory of Refractory Material and Metallurgy,Wuhan University of Science and Technology,Wuhan 430081,Hubei,China;Engineering Steel Institute,Central Iron and Steel Research Institute Co.,Ltd.,Beijing 100081,China)

机构地区：[1]武汉科技大学省部共建耐火材料与冶金国家重点实验室,湖北武汉430081 [2]钢铁研究总院有限公司工程用钢研究院,北京100081

出　　处：《钢铁》2024年第11期153-164,共12页Iron and Steel

摘　　要：利用室温拉伸和低温冲击试验,结合SEM、TEM、XRD和EBSD等分析,研究了合金元素Co对NiCrMoV系海工钢微观组织、第二相析出以及力学性能的影响。结果表明,经淬火和回火处理后,NiCrMoV钢显微组织主要为回火马氏体和少量逆转变奥氏体,由于钢中Co含量的增加,马氏体相变的畸变能降低,Ms温度(冷却过程开始生成马氏体的起始温度)升高,回火过程中马氏体逆相变得到的奥氏体减少,使得逆转变奥氏体含量随钢中Co含量的增加而降低。NiCrMoV钢回火过程中主要析出了细针状m_(2)C相和少量近球状M3C相,钢中添加Co主要促进了富Cr、Mo元素的m_(2)C相析出,这是因为Co大量固溶提高了Cr、Mo在钢中的过饱和度,增强了碳化物析出的驱动力,促进Cr、Mo以m_(2)C相析出;同时Co会延迟位错亚结构的回复,使钢中位错密度增加,提供了更多的第二相形核位置。经580℃回火,0Co、4Co和8Co钢的屈服强度分别为1 141、1 216、1 310 MPa,NiCrMoV钢中每添加质量分数为1%的Co,屈服强度提升约20 MPa。强化机制分析表明,NiCrMoV钢中添加Co主要是通过固溶强化和析出强化机制来提高材料强度。0Co、4Co和8Co钢的-84℃冲击功分别为76、52、11 J,Co对NiCrMoV钢的低温韧性有一定的恶化作用,一方面是由于钢中逆转变奥氏体减少,对裂纹扩展的钝化作用减弱;另一方面可能是因为Co的大量固溶使得Ni、Mn等元素在界面位置偏聚,使晶界能量增大,增加了裂纹形成的可能性。The influence of alloy element Co on the microstructure,second-phase precipitation behavior,and mechanical properties of NiCrMoV marine steel was studied using room-temperature tensile and low-temperature impact tests combined with SEM,TEM,XRD,and EBSD analysis.The results show that after quenching and tempering,the structure of NiCrMoV steel is mainly formed of martensite and a small amount of reverted austenite.Co increases the hardenability of steel and raises Ms point temperature.This decreases the amount of austenite transformed reversely from martensite during tempering with increasing Co content in the steel.During the tempering process of NiCrMoV steel,the primary precipitates are fine needle-like M2C phase and a small amount of spherical M3C phase.The addition of Co improves the precipitation of Cr-rich and Mo-rich M2C phase.The solid solution of Co increases the saturation of Cr and Mo,enhancing the driving force of carbide precipitation and promoting the precipitation of Cr and Mo as M2C phases.At the same time,Co will delay the recovery of dislocation substructures,increase the dislocation density in the steel,and provide more second phase nucleation positions.After tempering at 580℃,the yield strengths of 0Co,4Co,and 8Co steels were 1141,1216,1310 MPa,respectively.For every 1%Co(mass percent)added to NiCrMoV steel,the yield strength increased about 20 MPa.The mechanism research shows that adding Co to NiCrMoV steel mainly improves strength through solid solution strengthening and precipitation strengthening.The impact energies at-84℃for 0Co,4Co,and 8Co steels were 76,52,11 J,respectively.Co has a certain deteriorating effect on the low-temperature toughness of the test steel.On the one hand,it is due to the reduction of reverted austenite in steel,which weakens the passivation effect on crack propagation.On the other hand,the solid solution of Co causes elements such as Ni and Mn to aggregate at the interface,increasing the energy of boundaries and promoting the possibility of crack formation.

关 键 词：NiCrMoV钢 CO 逆转变奥氏体 m_(2)C相 强韧化机理 

分 类 号：TG142.1[一般工业技术—材料科学与工程]