Stainless steel binder for the development of novel TiC-reinforced steel cermets

Steel reinforced TiC composites are an attractive choice for wear resistance and corrosion resistance applications. TiC- reinforced 17-4PH maraging stainless matrix composites were processed by conventional powder metallurgy （P/M）. TiC-reinforced maraging stainless steel composites with 〉97% of theoretical density were fabricated. The microstructure, mechanical and wear properties of the composites were evaluated. The microstructure of these composites consisted of spherical and semi-spherical TiC particles. A few microcracks appeared in the composites, showing the presence of tensile stress in the composites produced during sintering. Typical properties, namely, hardness and bend strength were reported for the sintered composites. After heat treatment and aging, the increase of hardness was observed. The increase of hardness was attributed to the aging reaction in the 17-4PH stainless steel. The precipitates appeared in the microstructure and were responsible for the increase in hardness. The specific wear behavior of the composites was strongly dependent on the content of TiC particles, the interparticle spacing, and the presence of hard precipitates in the binder phase.     

Influence of secondary carbide precipitation and transformation on abrasion resistance of a 3Cr15Mo1V1.5 white iron

The relationship between the secondary carbide precipitation and transformation of the 3Cr15Mo1V1.5 white iron and abrasion resistance was investigated by using optical microscope （OM）, transmission electron microscopy （TEM） and X-ray diffrac- tion （XRD）. The results show that the properties of secondary carbides precipitated at holding stage play an important role in the abrasion resistance. After certain holding time at 833 K subcritical treatment, the grainy （Fe, Cr）23C6 carbide precipitated and the fresh martensite transformed at the holding stage for 3Cr15Mo1V1.5 white iron improve the bulk hardness and abrasion resistance of the alloy. Prolonging holding time, MoC and （Cr, V）2C precipitations cause the secondary hardening peak and the corresponding better abrasion resistance. Finally, granular （Fe, Cr）23C6 carbide in situ transforms into laminar M3C carbide and the matrix structure transforms into pearlitic matrix. These changes weaken hardness and abrasion resistance of the alloy sharply.     

固溶温度对含铜钢时效行为的影响

利用透射电子显微镜观察了Fe-Cu(w(Cu)=1.12%)高纯净钢不同温度固溶处理后的组织,借助维氏硬度计测量了实验钢的时效硬度,研究了固溶温度对其时效行为的影响.结果表明,固溶处理后铜并非均匀分布于基体中,而是以一种不均匀的短程有序畴形式存在,其结构特征对随后的时效行为具有显著影响.     

含W的Cr15型超级马氏体不锈钢组织性能分析

采用全自动热膨胀相变仪、光学显微镜、透射电镜、高分辨电镜及能谱分析和力学万能试验机等手段,研究含W的Cr15型超级马氏体不锈钢经淬火+回火后的微观组织和力学性能.结果表明,淬火+回火后的微观组织为回火马氏体及分布在马氏体基体中的逆变奥氏体两相组织,形成的逆变奥氏体与马氏体板条符合K-S关系.在基体上弥散析出的纳米级金属化合物Laves相以及富铜相ε-Cu起到强化作用.该钢具有优良的力学性能,洛氏硬度为26～36,抗拉强度为895～1 009 MPa,延伸率为17%～21%.     

Influences of copper on solidification structure and hardening behavior of high chromium cast irons

The influences of copper on microstructure and the hardening behavior of high chromium cast irons subjected to sub-critical treatment were investigated. The results show that the microstructure of the as-cast high chromium cast irons consists of retained austenite, martensite and M1C3 type eutectic carbide. When copper is added into high chromium cast irons, austenite and carbide contents are increased. The increased addition of copper content from 0% to 1.84% leads to the increase of austenite and carbide from 15.9% and 20. 0% to 61.0% and 35.5% , respectively. In the process of sub-critical treatment, the retained austenite in the matrix can be precipitated into secondary carbides and then transforms into martensite in cooling process, which causes the secondary hardening of the alloy under sub-critical treatment. High chromium cast irons containing copper in sub-critical treatment appear the second hardening curve peak due to the precipitation of copper from supersaturated matrix.     

Evolution of carbides and carbon content in matrix of an ultra-high carbon sintered steel during heat treatment process

DTA, thermal expansion, XRD, and SEM were used to evaluate the effect of quenching temperature on the mechanical properties and microstructure of a novel sintered steel Fe-6Co-1Ni-5Cr-5Mo-1C. Lattice parameters and the mass fraction of carbon dissolved in the matrix of the steel quenched were investigated. It is discovered that the hardness of the steel increases with quench-ing temperature in the range of 840-900℃ and remains constant in the range of 900 to 1100℃. It decreases rapidly when the tem-perature is higher than 1100℃. The mass fraction of carbon dissolved in the matrix of the steel quenched at 840℃ is 0.38, but when the quenching temperature is increased to 1150℃, it increases to 0.98. The carbides formed during sintering are still present at grain boundaries and in the matrix of the steel quenched at low quenching temperatures, such as 840℃. When the quenching temperature is increased to 1150℃, most of the carbides at grain boundaries are dissolved with just a small amount of spherical M23C6 existing in the matrix of the quenched steel.     

10CrMo910钢老化过程中的巴克豪森效应

基于Larson-Miller参数对10CrMo910钢进行了不同时段的高温加速老化模拟实验,运用光学显微镜(OM)和透射电子显微镜(TEM)对试样进行了显微组织观察,并研究了显微组织变化和不同老化程度对巴克豪森噪声(BN)的影响.结果表明,随高温加速老化时间的增加,老化过程中的主要组织结构变化为珠光体的消散与分解,碳化物自基体中析出与长大并向晶界迁移,晶粒亦有所长大,与此同时,位错密度则显著下降.与之对应的巴克豪森噪声检测结果显示,随着老化程度的增加,其BN振铃计数率呈逐渐降低趋势,作者从磁畴结构的角度并结合显微组织的变化对此进行了详细的分析并指出,老化过程中磁畴壁数目的减少是其最为主要的原因.     

动态时效对Al-Cu-Mg-Ag合金组织与力学性能的影响

对Al-Cu-Mg-Ag新型耐热铝合金进行预时效+中温轧制变形+终时效的动态时效工艺处理,采用硬度测试、拉伸性能测试,结合金相显微组织分析和透射电子显微分析,探究动态时效对其力学性能与微观组织的影响。结果表明：动态时效能够提高合金的时效硬化速率,随着变形量的增大,合金的峰时效时间逐渐减小,峰值硬度逐渐增大。动态时效能够改变晶粒形貌,随着变形量的增大,晶粒的纵横比增大,位错数量增多,强化相数量增多尺寸减小,使得合金强度随着变形量的增大而逐渐增大,但伸长率逐渐减小。变形量为50%合金的强度最高,抗拉强度和屈服强度最大,分别为527.4 MPa和467.0 MPa,伸长率保持在较高值9.1%。     

热老化对核级316LN锻造控氮奥氏体不锈钢微观组织及性能的影响

研究了热老化对核级316LN锻造奥氏体不锈钢的位错组态、电阻率及显微硬度的影响规律。结果表明,随着热老化的进行,奥氏体基体中位错密度总体下降,而始于晶界向晶内延伸的扩展位错数量增多且宽度变窄,其中,固溶态的扩展位错宽度约为1．0μm,热老化5000h后约为0．2μm。分析认为,碳原子在晶界及其附近微区的偏聚是引起位错亚结构变化的主要原因：电阻率随热老化时间的延长、检测温度的升高而增大,且热老化5000h后电阻率随温度的增长速率高于固溶态;晶内和晶界处的显微硬度值随热老化的进行均有所升高,二者之间显微硬度的差值逐渐增加。     

Mechanical properties and microstructure changes after long-term aging at 700℃ for a nickel-base superalloy

Mechanical properties and microstructure changes have been investigated on a new nickel-base superalloy after long-term aging at 700℃ It is found that the major precipitates of the tested alloy are MC, M23C6, M6C and in the course of long-term aging at 700℃. The carbides maintain good thermal stability with the aging time up to 5008 h. The growth rate of gamma prime precipitates is relatively high in the early aging period and then slows down. The coarsening behavior of gamma prime follows a diffusion-controlled growth procedure. The room temperature Rockwell hardness of the alloy aged at 700C increases slightly at the initial stage of aging, but it decreases with the prolonged time. It mainly depends on the size of gamma prime. In comparison with Nimonic     

高纯低碳铜钢固溶处理的研究

为了使含铜高纯低碳钢进行时效强化,有必要研究时效前的固溶处理.研究了固溶处理工艺对固溶态组织、硬度的影响,应用高分辨电镜研究了含铜高纯低碳钢的固溶态的组织结构特征.结果表明,该钢固溶处理后得到铜分布不均匀的铁素体组织,这种过饱和固溶体是由大量的有序畴组成的.     

合金元素对Cu-Te-Cr合金时效组织与性能的影响

采用扫描电镜(SEM)、X射线衍射仪(XRD)、电子能谱(EDS)分析Cu-Te-Cr合金时效析出相的形貌与组成,研究合金元素对Cu-Te-Cr合金时效组织与性能的影响。结果表明,时效过程中Te、Cr以多元化合物或细小的单质Cr析出,合金的硬度明显升高,随时效温度的升高,Cr粒子长大,共格度降低;同时基体晶粒内,部分析出相重溶,使合金硬度下降;由于Cr和Te两种元素互不相溶,其交互作用生成CrxTey化合物,随着Te含量的增加,铸造过程中生成这种化合物越多,减少Cr元素在铜基体的固溶度,从而合金硬度下降,而导电率有所提高。     

钢的退火软化机理

分析了钢的退火软化机理,指出钢的退火软化应从固溶体强化、位错强化、细晶强化等方面降低对铁素体基体的硬化作用,同时使钢呆的出的碳化物球状化、对Ｈ１３钢退火碳化物颗粒的平均直径、弥散度一硬度的 研究表明在碳化物体积分数一定时,硬度是碳化物颗粒平均直径的函数,颗粒直径越大,退火硬度越低     

AISI 304奥氏体不锈钢活性屏离子渗碳

利用活性屏离子热处理技术对AISI 304奥氏体不锈钢进行低温离子渗碳(AS-PC)处理,可以在不锈钢表面形成一层无碳化铬析出的碳的过饱和固溶体(Sc相)。处理后的奥氏体不锈钢可以在不降低耐蚀性能的基础上大幅度提高不锈钢表面的硬度,并解决了不锈钢直流离子渗碳温度均匀性差,工件存在边缘效应等问题,ASPC渗碳试样表面基本可以保持原色。     

多弧离子镀TiN涂层工艺及耐蚀性研究

为提高4Cr13马氏体不锈钢的耐蚀性,对其进行多弧离子镀处理,获得TiN涂层,并用X射线衍射仪、显微硬度计、扫描电子显微镜、电化学测量仪对涂层进行物相分析、表面形貌观察、硬度检测以及电化学腐蚀性能测试.结果表明:随着电流的增大,表面的液滴数目和尺寸增大,涂层厚度增加,薄膜硬度也增大;相结构主要为TiN,有明显的择优取向,且随着弧电流的增强,衍射峰强度略有增加.TiN试样在3.5％的NaCl溶液中耐蚀性与基体相当,在1 mol/L的H2SO4溶液中的耐蚀性比基体提高了800倍.     

高温时效对异质接头碳迁移和组织的影响

电站锅炉的对流管束通常使用奥氏体不锈钢与低合金耐热钢的焊接,两种材料在成分和组织上明显不同,异质接头在高温服役中会发生碳迁移现象,形成一个增碳区和脱碳区,对异质接头进行500℃／100h高温时效处理,观察熔合线两侧成分和组织的变化,结果表明,在高温时效处理后,在熔合区碳含量增加并且析出大量碳化物,焊态下母材热影响区粒状贝氏体和上贝氏体退化,转变成铁素体和索氏体。     

类激光熔覆Stellite合金沉积层的组织及磨损性能

为了进一步提高316不锈钢的表面性能,采用类激光熔覆技术在316不锈钢表面制备了Stellite合金沉积层.利用扫描电子显微镜、能谱仪、X射线衍射仪、显微硬度计与销盘磨损试验机,研究了Stellite合金沉积层的微观组织、化学成分、显微硬度及摩擦磨损性能.结果表明,Stellite合金沉积层主要由γ-Co和M_(23)C_6相组成.沉积层组织依附于316不锈钢基体的界面呈外延生长,由界面至表面依次呈平面晶、柱状晶和胞状树枝晶形态,且越靠近表面组织越细小.Stellite合金沉积层的最高硬度可达650 HV.在摩擦磨损过程中摩擦系数随着法向载荷的增大而减小,磨损机制主要为黏着磨损、磨粒磨损和氧化磨损.     

热处理对00Cr20Ni18Mo6Mn0.2V0.8Si0.1不锈钢组织与性能的影响

研究了固溶时效热处理对00Cr20Ni18Mo6Mn0.2V0.8Si0.1耐海水腐蚀不锈试验钢组织与性能的影响.结果表明：试验钢在固溶温度为1100℃、固溶时间为2 h、时效时间为4 h的热处理条件下,其综合力学性能最佳,其抗拉强度、延伸率、硬度最大值分别为642 MPa、27.1%、93.3HRB,与铸态相比,强度提高了12.6%,延伸率提高了54.8%.     

Effect of valence electron structure on temper process and hardness of the supersaturated carburized layer

By measuring the hardness of carburized layer of a new type supersaturated carburizing steel (35Cr3SiMnMoV) at different temper temperature for 2 h, the relationship curve between the carburized layer hardness and the temper temperature is established. The result indicates that the hardness goes down firstly, then up and down, just like a wave consistent with the temperature increase. A secondary hardening peak appears at 570 °C or so. Based on Empirical Election Theory (EET) of Solids and Molecules, the valence electron structures (VESs) containing α-Fe-C, α-Fe-C-Me segregation structure units and carbide are calculated. The laws of temper process and hardness change with the temper temperature are explained, and the fact that reconstruction of θ-Fe₃C is prior to that of special carbide at high tempering is analyzed with the phase structure formation factor, S, being taken into consideration. Therefore, the laws of temper process and hardness change of supersaturated carburized layer at different temper temperature can be traced back to valence electron structure (VES) level of alloy phase.     

长期热老化对铸造奥氏体不锈钢断裂韧性的影响

为了研究热老化对铸造奥氏体不锈钢断裂韧性的影响及其微观机理,按照ASTME1820-05a等实验标准,采用标准C（T）试样对Z3CN20.09M铸造奥氏体不锈钢进行了热老化断裂韧性测量.结果表明：Z3CN20.09M铸造奥氏体不锈钢的断裂韧性随热老化时间的增加呈现下降趋势;通过SEM观察断口发现,断裂机制由原始态的微孔聚集型断裂转变为解理断裂和微孔聚集断裂的混合断裂;断裂韧性J值与热老化时间t满足幂指数关系.对该材料制造的主管道的热老化断裂韧性做出外推预测.