Cr-Mn-N奥氏体耐热钢中M_(23)C_6型碳化物析出特征及其对韧塑性的影响  

PRECIPITATION BEHAVIOR OF M_(23)C_6 AND ITS EFFECTS ON DUCTILITY AND TOUGHNESS OF A NOVEL Cr-Mn-N AUSTENITIC HEAT RESISTANT STEEL

作　　者：郑雷刚[1] 胡小强[1] 康秀红[1] 李殿中[1] 

机构地区：[1]中国科学院金属研究所沈阳材料科学国家(联合)实验室,沈阳110016

出　　处：《金属学报》2013年第9期1081-1088,共8页Acta Metallurgica Sinica

摘　　要：利用OM,SEM与XRD物相分析等方法,研究了一种C和N含量相近的Cr-Mn-N奥氏体耐热钢在600—1000℃温度范围内时效过程中析出相的析出特征及其对材料韧塑性的影响.结果表明,实验钢中时效析出相主要为富Cr的M(23)C6型碳化物,且具有连续膜状、层片状、短杆状、颗粒状等典型形貌特征,析出序列为"晶界膜状析出→胞状组织内层片状析出-→晶内短杆状析出".此外,实验钢的时效脆性与M(23)C6型碳化物的析出特征密切相关.晶界处呈连续膜状特征的M(23)C6型碳化物显著降低实验钢的冲击韧性,是造成时效脆性的主要因素.Cr-Mn-N austenitic heat resistant steels have bright future in wide applications due to their lower cost, excellent mechanical properties, and outstanding local corrosion resistance after substituting the nickel partly or completely by the Mn, N and C elements. As the content of C or N elements increasing in Cr-Mn-N steels, a large quantity of precipitates form during hot working, resulting in embrittlement of these steels. In the present study, a new Cr-Mn-N austenitic heat resistant steel was aged at temperatures from 600 ~ to 1000 I~ in duration from 10 min up to 6000 min. By OM, SEM and XRD, the microstructure evolution of precipitates and their effects on ductility and toughness of the studied steel were investigated. The results indicated that precipitates formed during aging were mainly Cr-rich M23C6 carbides, whose morphologies changed in a sequence of intergranular films, lamellae in cellular microstructure and intragranular rods or particles with the increase of aging time and/or temperature. The time-temperature-precipitation （TTP） curves for M23C6 carbides were determined, which have a typical C-shaped profile with a nose temperature between 850 ℃ and 900 ℃, and an incubation period not more than 1 min. In addition, it was found out that the aging embrittlement of the studied steel is strongly dependent on the morphology of M23C6 carbides. The intergranular film-shaped M23C6 carbides were considered as the main factor to favor cracks rapidly expanding along grain boundaries, finally resulting in brittle intergranular fracture.

关 键 词：Cr—Mn-N奥氏体耐热钢 M23C6型碳化物 胞状组织 时效脆性 

分 类 号：TG142[一般工业技术—材料科学与工程]