李见
,
孙旭东
,
李在先
,
李春生
金属学报
<正> Unthank等人曾指出,含Cr高的奥氏体不锈钢在600～800℃氮化时,将沿晶界形成大量的CrN,并可能导致沿晶开裂,造成氮化层剥落.Kindlimann和Ansell认为,氮化表面上Fe或Ni-Fe的氮化物增到一定厚度时将产生“白亮层”,冷却时可能剥落。高濑孝夫在讨论氮化温度对18-8钢氮化层脆性影响时指出,低温氮化易出现氮化层剥落。本工作通过氮化前对试样作适当的预先热处理找到了解决氮化层剥落的方法,并探明了氮化层剥落的原因。
关键词:
钢的氮化
,
spalling
,
heat resistant steel
Xiaoqiang Hu Namin Xiao Xinghong Luo Dianzhong Li
材料科学技术（英文）
Thermodynamic calculation, thermal analysis, and identification and observation of precipitates have been carried out on a W-alloyed 10 wt pct Cr steel by means of ThermoCalc program, differential thermal analysis (DTA), X-ray diffraction (XRD) and transmission electron microscopy (TEM) with an energy dispersive X-ray spectrometer, respectively. Several critical phase transformation points were determined by combining experimental results with calculations. Two individually stable phases of Nb(C, N) and VN, instead of one single phase MX (X: C, N), M23C6 or Laves phases, were predicted in the calculated equilibrium phase diagram. An unstable elongated M7C3 with relatively higher Cr was detected unexpectedly in the normalized and tempered steel. Two kinds of spherical Nb(C, N) with different size were recognized as the primary and the secondary precipitates of Nb(C, N) which contain different V contents. It was observed that one kind of complex precipitate in a special V-wing shape was resulted from two plate-like VN adhering to coarse primary spherical Nb(C, N).
关键词:
Heat resistant steel
,
9-12%Cr steel
,
phase transformation
,
microstructure
,
MX precipitate
Xiaoqiang Hu Namin Xiao Xinghong Luo Dianzhong Li
材料科学技术（英文）
Thermodynamic calculation, thermal analysis, and identification and observation of precipitates have been carried out on a W-alloyed 10 wt pct Cr steel by means of ThermoCalc program, differential thermal analysis (DTA), X-ray diffraction (XRD) and transmission electron microscopy (TEM) with an energy dispersive X-ray spectrometer, respectively. Several critical phase transformation points were determined by combining experimental results with calculations. Two individually stable phases of Nb(C, N) and VN, instead of one single phase MX (X: C, N), M23C6 or Laves phases, were predicted in the calculated equilibrium phase diagram. An unstable elongated M7C3 with relatively higher Cr was detected unexpectedly in the normalized and tempered steel. Two kinds of spherical Nb(C, N) with different size were recognized as the primary and the secondary precipitates of Nb(C, N) which contain different V contents. It was observed that one kind of complex precipitate in a special V-wing shape was resulted from two plate-like VN adhering to coarse primary spherical Nb(C, N).
关键词:
Heat resistant steel
,
9-12%Cr steel
,
phase transformation
,
microstructure
,
MX precipitate
陈国宏
,
白小龙
,
刘俊建
,
王家庆
,
汤文明
材料热处理学报
HR3C及T92两种典型超(超)临界机组耐热钢分别在650 ～ 700℃进行高温时效,研究时效过程中显微组织结构和硬度的变化规律,建立硬度与Larson-Miller参数(P函数)间关系数学模型.结果表明,两种耐热钢的硬度均随时效温度升高显著降低;温度不变,随着时效时间的延长,HR3C耐热钢的硬度先增加后减小,而T92钢硬度单调下降,最后都趋于稳定.孪晶界消失以及晶界与晶内析出相的析出、长大是导致时效过程中两种耐热钢硬度变化的主要原因.采用线性拟合的方法,得到了时效耐热钢硬度与其P函数关系模型.基于相同P函数,计算所得时效钢硬度与测量的硬度吻合,该模型可用于服役耐热钢管服役寿命预测.
关键词:
耐热钢
,
高温时效
,
硬度
,
P函数
,
服役寿命
王航
,
王建军
,
韩礼红
,
田志华
,
谢斌
材料热处理学报
通过室温、高温拉伸、Gleeble热模拟试验,光学显微镜(OM)及高分辨透射电镜(HR-TEM)观察,研究了中温低合金(Cr-Mo、Cr-Mo+微合金)耐热钢的拉伸、蠕变行为及其微观机理.结果表明,高温270℃下,低合金耐热钢拉伸应力-应变曲线的屈服平台消失,形成连续光滑的应变强化曲线.相比于C-Mn钢,低合金耐热钢的高温强度明显升高.高温350℃下,相比于C-Mn钢,低合金耐热钢的蠕变速率明显降低,其中Cr-Mo+微合金钢的蠕变速率最小.微合金元素形成的强碳化物抑制了Cr、Mo合金元素从基体中析出,Cr-Mo+微合金钢的蠕变抗力得到提高.
关键词:
低合金耐热钢
,
蠕变
,
碳化物
,
微合金
程从前
,
刘宜萱
,
赵杰
机械工程材料
采用电化学阻抗试验、氧化增重法分析了Super304H、P92、15CrMo钢在554,645℃及24 MPa超(超)临界水中氧化44 h后的电化学性能和抗氧化性能,并用SEM和XRD对氧化膜的表面形貌及物相组成进行了分析.结果表明:Super304H钢氧化后没有明显的质量变化,P92钢和15CrMo钢有氧化增重现象,但氧化增重的差异不明显;Super304H钢表面由细小的针状或颗粒状的含铁和铬的氧化物组成,P92钢和15CrMo钢表面为相对较大的颗粒状Fe3O4组成;554℃超临界水氧化后在NaCl溶液中的阻抗由小至大顺序为P92、Super304H、15CrMo钢,随温度升高阻抗增大;电化学阻抗可在短时氧化条件下有效分析耐热钢的抗氧化特性.
关键词:
耐热钢
,
超临界水
,
氧化
,
电化学阻抗
岳增武
,
傅敏
,
李辛庚
,
田学雷
机械工程材料
在自制的水蒸气氧化装置中,对两种具有不同晶粒度的P91钢进行了水蒸气等温氧化试验,对表面氧化膜进行了形貌观察、能谱分析和X射线衍射分析.结果表明:两种P91钢的氧化动力学曲线均具有抛物线特征,在650℃氧化300 h后,粗晶粒钢的氧化质量增加明显高于细晶粒钢的;两种钢氧化结果的差异是由于细晶粒P91钢在氧化初期(30 h内)能更快地形成富铬的氧化层,阻碍了铁离子的向外扩散,从而有效地降低了氧化速率.
关键词:
水蒸气
,
氧化
,
晶粒度
,
扩散
,
耐热钢
王岗
,
胡正飞
材料热处理学报
以热电厂服役时间长达230000 h的主蒸汽管道X20马氏体耐热钢为研究对象,通过室温和服役高温的力学性能测试、组织以及亚结构和析出相的SEM、TEM观察、电解萃取相XRD物相分析等,研究了耐热钢长期服役的力学性能和显微结构变化.结果表明:服役钢除室温冲击性能下显著下降外,其他的力学性能退化并不显著.服役后材料的组织仍为典型的马氏体,但马氏体组织粗化明显,出现板条碎化,板条界移动,位错密度下降,碳化物粗化等现象.服役前后材料中碳化物形态和种类出现明显变化,耐热钢中主要碳化物M23C6长期服役后粗化显著,原始态中存在的亚稳态碳化物M2C及M6C和部分MX溶解,析出了Laves相和Z相.
关键词:
X20耐热钢
,
微观组织
,
电解萃取
,
碳化物
,
退化
