奥氏体不锈钢循环离子氮氧共渗工艺研究

对OCr18Ni9奥氏体不锈钢进行氮氧共渗循环离子渗氮试验,并和常规离子渗氮进行对比.利用光学显微镜、显微硬度计、XRD及磨损仪对渗氮层进行分析.结果表明,氮氧共渗循环离子渗氮比常规离子渗氮的渗氮速度快,渗层比常规离子渗氮厚;表面硬度为920 HV0.05(比常规离子渗氮高20 HV0.05),硬度梯度平缓;渗层中的ε相减少,γ'相增多;且渗层中的微量Fe3O4降低了表面摩擦系数,使工件经氮氧共渗循环离子渗氮后获得更高耐磨性.     

304 不锈钢低温离子渗氮及氮碳共渗处理

目的研究304不锈钢离子渗氮层和氮碳共渗层的组织、硬度及耐磨、耐蚀性能,并考察渗层的磨损机理。方法利用离子渗氮及氮碳共渗工艺在304不锈钢表面获得硬化层,利用XRD,OM及共聚焦显微镜、显微硬度仪、电化学测试仪,分析处理前后渗层的组织、相结构及渗层的硬度及耐磨耐蚀性能。结果 304不锈钢氮碳共渗和渗氮层主要为S相层,在相同工艺条件下,氮碳共渗工艺获得的渗层为γN+γC的复合渗层,且厚度大于单一渗氮层。渗氮层和氮碳共渗层硬度约为基体硬度的3.5倍。在干滑动摩擦条件下,氮碳共渗层比渗氮层具有更好的耐磨性能;渗氮层的磨损机理为磨粒磨损的犁沟效应和断裂,氮碳共渗层的磨损机理为磨粒磨损的犁沟和微切削。电化学测试表明,渗氮层和氮碳共渗层的耐蚀性能均优于基体。结论 304不锈钢在420℃进行离子渗氮和氮碳共渗处理后,硬度和耐磨性能可大幅提高,且氮碳共渗处理效果更佳。     

等离子渗镀TiN/TiCN多涂层的力学和摩擦磨损性能

采用等离子渗镀复合处理技术在DC53模具钢表面制备出TiN/TiCN多层涂层,重点研究了等离子渗氮(PN)和等离子氮碳共渗(PNC)工艺对随后的电弧离子镀TiN/TiCN涂层的力学性能和摩擦磨损性能的影响。结果表明:经等离子渗氮和等离子氮碳共渗处理后,模具钢基体表面均形成Fe_3N和γ'-Fe_4N化合物。等离子渗氮(等离子氮碳共渗)-电弧离子镀复合处理工艺制备的TiN/TiCN多层涂层的硬度和结合强度明显优于单一的TiN/TiCN多层涂层样品。由于等离子氮碳共渗硬化层中存在较多的γ'-Fe_4N硬质相,有利于面心立方结构氮化物涂层外延生长,改善了涂层体系的承载能力,耐磨损性能得到显著提升。     

低温离子氮碳共渗温度对AerMet100钢摩擦学性能的影响

研究了不同温度对AerMet100钢渗氮层和氮碳共渗层的显微组织、表面硬度、渗层截面硬度梯度以及耐磨性的影响,并考察了渗层的磨损机理。结果表明,氮碳共渗层相较于渗氮层表面生成的化合物更加细小,表面更加平整光滑;离子渗氮、离子氮碳共渗处理都可显著提高AerMet100钢的表面硬度;随着温度的增加,共渗层厚度也明显增加;氮碳共渗层比渗氮层具有更低的摩擦因数,在共渗温度为480 ℃时氮碳共渗试样具有最低摩擦因数和磨损率,表现出最佳的耐磨性。渗氮层的磨损机理为氧化磨损和表面疲劳磨损,氮碳共渗层的磨损机理为氧化磨损、磨粒磨损以及表面疲劳磨损。     

喷砂预处理与离子氮碳氧硫复合工艺

按照不同共渗工艺参数,分别对38CrMoAl钢试样进行喷砂预处理离子氮碳氧硫共渗复合处理和离子氮碳氧硫共渗处理.结果表明,喷砂预处理离子氮碳氧硫共渗复合工艺有利于缩短共渗时间和降低共渗温度;在相同的共渗介质与共渗参数下,喷砂预处理离子氮碳氧硫共渗复合处理的表面硬度可达913 HV0.2,渗层厚度大约为0.33 mm,比离子氮碳氧硫共渗分别增加了35％和43％;经喷砂预处理离子氮碳氧硫共渗复合处理后耐腐蚀性增加.     

38CrMoAl钢喷丸预处理与稀土催渗等离子多元共渗复合工艺研究

目的探索38CrMoAl喷丸预处理与稀土离子多元共渗复合强化新工艺的效果及其机理。方法通过设计正交实验筛选出最优处理工艺,在最优工艺参数条件下进行对比试验,分别测定渗氮后各试样的表面硬度及渗层厚度,观察其金相组织,利用SEM和能谱分析研究每组试样渗氮层的性能及产生原因。结果 38CrMoAl钢喷丸预处理与稀土催渗离子多元共渗的最优工艺参数为:渗氮温度540℃,氨气流量2.0 L/min,保温时间9 h。38CrMoAl钢试样的最大硬度为1221HV,渗层厚度为355μm。38CrMoAl钢试样的金相显微组织分析表明,喷丸预处理、稀土催渗对等离子多元共渗有促进作用,两者复合工艺的多元共渗作用效果大于单一稀土催渗和等离子多元共渗工艺。38CrMoAl钢试样渗层的能谱检测结果显示,复合处理工艺与单一处理工艺相比,在同一深度渗入的氮、碳、氧元素含量以及渗层深度均有明显提高。结论喷丸预处理与稀土催渗离子多元共渗工艺优于普通多元共渗和稀土多元共渗,喷丸和稀土的复合处理可以显著增强渗层厚度和渗入元素含量,有利于材料表面性能的提升。     

球铁曲轴加氧渗氮工艺研究

球铁曲轴常常由于渗氮层薄、质量不稳定而引起断裂失效，本课题研究了球铁曲轴加氧渗氮工艺。对球铁试样经570℃、580℃，不同氨气流量和氧加入量渗氮4h后的表面硬度、渗层深度及渗层组织进行分析，结果表明，加氧渗氮可获得比常规气体氮碳共渗更高的表面硬度和渗层深度。优选出的适合于球铁曲轴的加氧渗氮工艺为：570℃保温4h，氨气流量2000L／h，氧气流量10L／h，炉压35mm水柱；或580℃保温4h，氨气流量1800L／h，氧气流量10L／h，炉压35mm水柱，二种工艺均可获得深度超过0．20mm、表面硬度600HV0．1以上的渗层。     

38CrMoAl钢钛催渗等离子氮化工艺研究

目的 探究38CrMoAl钢钛催渗等离子渗氮工艺及机理.方法 在其他工艺参数确定的情况下,通过常规等离子渗氮与钛催渗等离子渗氮处理对比试验,研究38CrMoAl钢钛催渗离子渗氮处理随渗氮时间的变化规律.对试样进行表面硬度、渗层深度检测和显微金相组织与SEM形貌的观察,探究不同处理工艺的催渗效果及钛催渗等离子渗氮的机理.结果 在渗氮的前3 h,渗氮层厚度增加明显,当渗氮时间超过3 h后,其氮化层的厚度便趋于饱和.对比不同时间(3、5、8 h)钛催渗等离子渗氮的表面硬度,差距不大.综合得出38CrMoAl钢在渗氮温度535℃、氨气流量2.0 L/min的工艺参数下,钛催渗等离子渗氮效率最优的渗氮时间为3 h,其表面硬度为1160.8HV,渗层深度为300μm,优于常规离子渗氮8 h的作用效果.结论 38CrMoAl钢试样经过钛催渗等离子渗氮后,渗层的表面硬度和深度明显高于常规离子渗氮.钛的加入可以促使合金元素向表面富集,有利于表面合金化,提升渗氮效率,增强渗氮效果.     

42CrMo钢的钛催渗等离子渗氮工艺

研究了不同渗氮时间下钛元素对42CrMo钢常规离子渗氮工艺的作用效果,表征分析了不同渗氮工艺下试样表面的渗层组织及性能。结果表明,钛催渗离子渗氮试样的表面硬度和渗层深度均明显高于常规离子渗氮。在535℃×3 h的工艺条件下,钛催渗离子渗氮试样渗层的表面硬度达到887.4 HV0.2,渗氮层厚度约为400μm。钛元素的加入促进了氮元素的渗透和扩散,在试样表面生成高硬度化合物TiN。相较于相同保温时间下的常规离子渗氮,钛催渗离子渗氮试样表面硬度提高了60 HV0.2,渗层厚度增加了80μm,渗氮效率提升了约25%。与常规离子渗氮相比,钛催渗离子渗氮工艺具有显著优势,不仅有利于改善渗层组织性能,增强渗氮效果,还提高了渗氮效率,使渗氮周期明显缩短。     

2Cr13钢氮碳氧硫变温离子共渗工艺及性能研究

从温度、时间、氨气流量和混合气(乙醇和二硫化碳混合液)流量方面研究2Cr13不锈钢氮碳氧硫变温离子共渗工艺,寻找最优的共渗参数,并与常规离子渗氮和变温离子渗氮相比较。利用显微硬度计、金相显微镜、X射线衍射仪和电化学工作站对试样进行分析。结果表明:2Cr13钢经535℃变温共渗8 h,氨气流量1.5 L/min,混合气流量0.25 L/min变温离子共渗处理,表面硬度达到硬化要求,共渗层厚度0.28 mm,梯度平缓;共渗层中微量的Fe3O4可降低摩擦系数,FeS具有储油减磨的特性,使工件耐磨性更好;另外,其耐腐蚀性略低于常规离子渗氮。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。