双相不锈钢中温脆化规律的研究

An Investigation on Embrittlement of Duplex Phase Stainless Steels Durlng Isothermal Heating at Intermediate Temperatures

研究了OCr 25Ni 5 Mo2,OCr 25Ni5Mo2N 和OCr 22NisMo3N 三种双相不锈钢由于中温(300～620℃)热处理而造成的脆化现象。结果表明,这三种双相不锈钢在此温区的脆化动力学曲线——等冲击功曲线都是两族相互连接的C 曲线:C 曲线族的交接处均在540—56o℃;脆化最快处发生在475℃左右。475℃脆化过程的表观激活能为160 kJ/mol,说明了475℃脆性发展的关键环节是铬原子的扩散。对试样断口形貌和精细组织的观察表明:双相钢在560℃以上处理时发生的脆化主要由碳氮化合物的析出所造成,而低温区的脆化则主要由α′相的析出所造成,碳氮有促进475℃脆性的作用。

The embrittlement of three grades duplex stainless steel aging at intermediate temperatures was investigated.Experimental results reveal that the kinetics of the embrittlement can be represented by two sets of C shaped isotoughness curves.The joints of the C carves are to be located at temperatures from 540-560℃.The apparent activation energies of 475℃ embrit- tlement of the all three steels were measured to be approximatically 160 kJ/mol.It is roughly equal to the activation energy of volume diffusion of Cr in a ferritic stainless steel.The embrit- tle microstructures of the three steels indicated that the embrittlement occurred at temperatures above 560℃ is largely due to precipitation of Cr_(23)C_6 and Cr_2N,and the formation of a(?) phase in the ferrits grains is the main cause of the embrittlement occurred at 475℃.