ZG40Cr25Ni20炉管服役后断裂韧性试验分析及断口微观形貌研究（英文）

将断裂力学原理应用到炉管寿命预测中。利用MTS810试验机,对服役3万h的炉管和未服役炉管的断裂韧性进行了试验分析,并利用扫描电镜进行了断口的形貌分析。研究结果表明:服役后炉管的断裂韧性与未服役炉管相比显著下降,抵抗裂纹扩展能力减弱;服役后的炉管断裂面没有裂纹稳态扩展区和宏观塑形变形,对应于断裂韧性的下降,断裂面微观形貌呈典型的脆性断裂特征。     

炉管材料ZG40Ni35Cr25Nb过早失效的原因分析

某石化公司制氢转化炉炉管在运行不到40 000 h后突然破裂起火,在经过宏观检测、表面探伤、力学性能测试,能谱、金相、电镜、X射线、应力等分析后得出结论:由于炉管材料晶界碳化物过多以及疏松空洞的存在削弱了韧性,产生了较多的微观裂纹,加上管外保温材料中存在较多的Na 、Cl-、K 、Mg2 、Ca2 ,便在下猪尾管到下支耳之间的应力较大部位,发生应力腐蚀开裂,58号炉管首先开裂泄漏起火,其它炉管在外部火焰烘烤下短时高温损伤,并变形鼓包直至开裂,这是失效的主要原因和过程.针对失效原因提出了今后使用过程中应采取的防护措施.     

Cr25Ni20耐热钢炉管的焊接

通过对Cr25Ni20耐热钢炉管的模拟焊接，制定出该钢管的手工电弧焊工艺。     

Cr9Mo炉管高温服役后性能测试及弯曲原因分析

通过宏观观察、硬度测试、金相分析、常温和高温拉伸试验、冲击试验和扫描电镜等方法,对高温服役后的Cr9Mo炉管进行性能测试,并分析弯曲原因.结果表明:炉管金相组织明显球化;常温下的伸长率,硬度和冲击性能有所下降,高温下的屈服强度和抗拉强度均比规范值低;热应力导致炉管弯曲.     

高锰钢低温脆性与微观断口形貌

对水韧状态及硬化状态的ZGMn13钢进行了系列冲击试验,结果表明:高锰钢冲击韧性随试验温度下降而降低,有明显的低温脆性。高锰钢微观断口有:韧窝断口、塑性沿晶断口、解理断口及混合断口。     

ZG40Cr25Ni20奥氏体耐热钢的烧损研究

采用光学显微镜(OM)、能谱仪(EDS)、X射线衍射仪(XRD)、高温显微镜原位观察等实验手段,分析了ZG40Cr25Ni20奥氏体耐热钢烧损原因。结果表明,随着温度升高,奥氏体晶粒不断长大,碳化物Cr23C6不断形成和长大,碳化物中的Cr含量和碳化物硬度不断增加,奥氏体基体中的Cr含量不断减少。温度过高,碳化物溶解,形成孔洞,促进微裂纹沿晶界的扩展,奥氏体晶粒间的结合力逐渐减弱,基体发生过烧,钢的结晶组织遭到破坏,失去金属原有的塑性和强度,造成高温耐热管失效,孔洞和微裂纹的形成及扩展是材料失效的主要原因。此外,高温显微镜原位观察和热处理实验结果表明,ZG40Cr25Ni20耐热钢中碳化物的溶解温度为1030~1250℃。高温显微镜原位观察为碳化物溶解观察和耐热钢失效分析提供了一种新的方法。     

镍基合金焊条ENiCrCoMo-1性能试验及微观形貌分析研究

对两个厂家的镍基合金焊条ENiCrCoMo-1进行了工艺性和熔敷金属性能对比试验,并对微观形貌进行了分析。试验结果表明,两个厂家的镍基合金焊条ENiCrCoMo-1工艺性能均良好,熔敷金属成分及力学性能均满足国标要求。此外,由于两个厂家镍基合金焊条ENiCrCoMo-1熔敷金属成分的差异,使其凝固树枝晶及析出相形貌和分布不同,从而导致其性能存在一定的差异。     

Al对ZG40Cr25Ni20耐磨性的影响

对Al含量为0、1.68%,4.72%和7.10%的ZG40Cr25Ni20进行了对比磨损试验.结果表明,Al的加入可以不同程度的提高材料的耐磨性能,Al含量为7.10%时耐磨性最好,其在相同条件下的耐磨性为不含Al时的2.62倍,其次为Al含量为4.72%,其耐磨性比Al含量为1.68%时提高66.40%,试验合金的磨损机理为微观切削.     

过滤净化对不锈钢ZG1Cr18Ni9Ti断裂韧性的影响

过滤净化可以提高不锈钢的塑性和韧性指标;它使断裂韧性提高的主要机理是过滤净化减少了夹杂物含量,以及疏松和气孔的数量,提高了合金的致密度,消除了部分裂纹源。     

ZG0Cr13Ni4Mo不锈钢铸件微观组织试验研究

以长江三峡水轮机叶片所用材料为研究对象，设计并浇注了两种类型的大型试件。用金相显微镜及扫描电镜观察了铸态下微观组织形态，测定了奥氏体晶粒大小、奥氏体晶粒内马氏体板条束个数和马氏体板条间距。分析了ZG0Cr13NiMo不锈钢铸件凝固相变过程，阐明了该材质最终微观组织的特点。试验结果和数值模拟结果对比，可以验证数值模拟结果的可信性。     

Effects of aging treatment on microstructure and mechanical properties of Cr25Ni35Nb and Cr35Ni45Nb furnace tube steel

Cr25Ni35Nb and Cr35Ni45Nb alloys are usually used in the ethylene cracking furnaces.However,premature failure of furnace tubes often occurs ahead of design life due to elevated temperature exposure conditions (1050-1100 ℃) and aggressive service environment.Effects of exposure temperature and time on microstructure and mechanical properties of Cr25Ni35Nb and Cr35Ni45Nb steel at aging temperature (1200 ℃) with various exposure time were simulated different service times at 1050 ℃.Change of mechanical propert...     

Investigations on the microstructure and room temperature fracture toughness of directionally solidified NiAl–Cr(Mo) eutectic alloy

The microstructures and room temperature fracture toughness of directionally solidified NiAl-xCr-6Mo (x = 28, 32 and 36 at%) alloys were investigated. Fully eutectic microstructure could be obtained in the alloys over a wide composition range. High temperature gradient could increase the planar/cellular transition rate and expand the eutectic coupled growth zone. The volume fraction of Cr(Mo) strengthening phase increased with the increasing content of Cr, accordingly, the fracture toughness of NiAl–Cr(Mo) alloys also gradually increased. The fracture toughness of 26.15 MPa m^1/2 was obtained in the NiAl-36Cr-6Mo hypereutectic alloy solidified at withdrawal rate of 10 μm/s and temperature gradient of 600 K/cm, which is the highest value in the NiAl–Cr–Mo alloy system until now. Well-aligned microstructure was beneficial to the enhancement of the fracture toughness, while the existence of primary phase seriously deteriorated the toughness. All the directionally solidified NiAl–Cr(Mo) alloy failed as brittle quasi-cleavage fracture. Some toughening mechanisms, such as crack bridging, crack nucleation, crack blunting, crack deflection, interface debonding and shear ligament toughening as well as linkage of microcracks were observed. In addition, mobile dislocation generated from the interface also had significant influence on the toughness.     

Microstructure and fracture toughness of Ti(C0.7N0.3)-WC-Ni cermets

Mo₂C is normally added to improve the wettability between Ti(C,N) and Ni in Ti(C,N)-based cermets. Due to the increasing price of Mo₂C, much attention has been paid to Ti(C,N)-based cermets with WC addition. In this paper, effect of WC content on the microstructure and properties of Ti(C_0.7N_0.3)-xWC-15wt.%Ni cermets free of Mo₂C was studied. The experimental results show that the microstructure is refined obviously with the increase of WC content. The fracture toughness decreases with the increase of WC content when WC content is 10-25 wt.%, and increases when WC content varies from 25 wt.% to 30 wt.%.     

TC4钛合金惯性摩擦焊接头组织及断裂韧性与裂纹扩展特性分析

文章采用了XRD、SEM、EBSD等显微表征技术分析了焊态及焊后热处理态下焊接接头各区域的微观组织特征,并研究了焊接接头的断裂韧性和疲劳裂纹扩展性能。结果表明,焊缝区以再结晶组织为主,热力影响区等轴状初生α_p相转变为棒状结构,热影响区组织与母材基本相同,热力影响区与热影响区的原始β晶粒内部分区域形成了取向差角度约为60°的针状马氏体α′相,热处理促进了残余亚稳态β相分解,在片状α_s相间形成了大量断续分布组织。焊缝区α晶粒内大量的平行或交叉分布的片状α相和复杂的相界面结构可有效阻碍裂纹的扩展并改变裂纹的扩展路径,提高焊接接头的断裂韧性及抗疲劳裂纹扩展能力。     

固溶处理对ZG40Cr25Ni20Si2耐热钢耐蚀性能的影响

采用动电位极化曲线、电化学阻抗谱、中性盐雾试验、光电子能谱研究了固溶处理(固溶温度1080℃,保温时间90 min)对ZG40Cr25Ni20Si2不锈钢耐腐蚀性能的影响.结果表明:在此固溶处理参数下,处理后的试样腐蚀电位下降,腐蚀电流密度升高,容抗弧尺寸明显低于铸态,耐腐蚀性能降低.中性盐雾试验中在96 h内固溶态和...     

Al对ZG40Cr25Ni20抗磨耐热钢高温抗氧化性的影响

在ZG40Cr25Ni20抗磨耐热钢中加入不同含量的Al,在900℃和1100℃下分别进行循环高温抗氧化性试验。通过不同温度下氧化增重测量、氧化动力学分析,以及试验后试样形貌观察,得出了Al对ZG40Cr25Ni20高温抗氧化性能的影响规律,结果表明适量的Al能明显提高ZG40Cr25Ni20的高温抗氧化性。     

20Cr2Ni4A钢的高强韧化工艺

根据低碳马氏体型钢20Cr2Ni4A的材料特点,通过提高冶金质量获得高纯净度及成分、组织均匀的原材料。结果表明,将有利于提高淬透性的成分控制在中上限、加入细晶元素,及采取930 ℃高温正火+610 ℃高温回火+900 ℃高温淬火+200 ℃低温回火的热处理工艺,获得回火马氏体组织,降低材料脆性转变温度及缺口敏感性,满足石油吊环用钢的高强和抗低温冲击要求。     

Microstructure evolution and room temperature fracture toughness of as-cast and directionally solidified novel NiAl-Cr(Fe) alloy

The microstructure evolution and room temperature fracture toughness of as-cast and directionally solidified NiAl-Cr(Fe) alloy were investigated using OM, SEM, EDS, DSC and three-point bending tests. From the as-cast microstructure and DSC result, NiAl-34Cr-4Fe (at.%) is a eutectic alloy which consists of eutectic cells in different sizes. The half-baked mesh-like structure is observed at the cell center, and the radial emanating thicker or longer Cr(Fe) phases embedded within NiAl matrix are observed near or at the cell boundary. In the directional solidification process, the solid-liquid interface morphology has an evolutionary process of planar to cellular, even dendritic interface with increasing the withdrawal rates, and the eutectic cell and the microstructure at the cell center refines gradually. From the transverse microstructure, the characteristic of eutectic cell is similar to that of eutectic cell in as-cast alloy. It can be seen from the longitudinal colony/cell center that the broken (short) Cr(Fe) rods are observed at 6 μm/s, and they evolve to granular Cr(Fe) phases when the withdrawal rate increases further. Moreover, regardless of vacuum induction melting (as-cast) and directional solidification, NiAl-34Cr-4Fe (at.%) eutectic alloy possesses a poor fracture toughness due to the inferior brittleness of both NiAl and Cr(Fe) phases. Meanwhile, the crack propagation and fracture surface are observed to better understand the fracture behavior.     

正火冷速对3.5Ni无缝钢管组织和性能的影响

对不同正火处理后的3.5Ni无缝钢管样品进行夏比低温冲击试验,利用金相显微镜、扫描电镜和透射电镜,观察其显微组织、断口形貌和析出组织。结果表明：随着正火冷速的增加,3.5Ni无缝钢管组织晶粒尺寸减小、形成粒状贝氏体组织,当正火冷速为25 ℃/s时,在细晶强化、相变强化等综合作用下, 3.5Ni无缝钢管低温韧性大幅提高,冲击吸收能量(-100 ℃)平均值达到82 J。