38CrMoAl钢循环等离子氮碳氧硫共渗工艺的研究

对38CrMoA l钢进行了常规等离子渗氮、循环等离子渗氮以及循环等离子氮碳氧硫共渗处理,研究这几种工艺对表面硬度、渗层组织、硬度梯度的影响。结果表明：循环等离子氮碳氧硫共渗有利于形成共渗元素进一步扩散的通道,加速共渗元素的渗入;综合表面硬度和渗层厚度,循环等离子氮碳氧硫共渗工艺明显优于常规等离子渗氮和循环等离子渗氮。     

离子氮铝共渗方法及对42CrMo钢组织性能的影响

目的 研发离子氮铝共渗试验方法,达到不影响42CrMo钢基体组织性能前提下,显著提高试样表面硬度和耐磨性效果。方法 采用电解法在42CrMo钢表面沉积氢氧化铝膜,再在520 ℃/4 h工艺下进行离子氮铝共渗处理,并在相同工艺参数条件与传统离子渗氮进行对比。用光学显微镜、维氏显微硬度计、摩擦磨损测试机、X射线衍射仪及SEM对截面显微组织、截面硬度、耐磨性及物相等进行了测试和分析。结果 获得了离子氮铝共渗试验方法,在520 ℃/4 h相同工艺参数下,离子氮铝共渗形成的化合物层和有效硬化层厚度比常规离子渗氮显著增加,其中,化合物层厚度由17.24 μm增加到52.13 μm,有效扩散层从175 μm增加到1 050 μm,相当于等离子处理效率提升6倍;同时,渗层形成了AlN及FexAl强化相,大幅度提高了渗层的硬度及耐磨性能。表面硬度由750HV0.025提高到1 250HV0.025,摩擦因数由常规离子渗氮0.52下降到0.29,磨损率由常规离子渗氮3.22×10^?5 g/(m.N)下降到1.21×10^?5 g/(m.N),磨痕明显减轻。结论 采用电解硝酸铝生成氢氧化铝沉淀附着在工件表面作为预处理,获得了离子氮铝共渗试验方法,与常规离子渗氮相比,离子氮铝共渗形成了多层次渗层结构,大幅度提高常规离子处理效率、表面硬度及耐磨性。     

工业纯铁的氮碳钛离子共渗工艺

针对氮、碳二元离子共渗电磁纯铁的渗氮层硬度低、耐磨性差的问题,采用氮、碳、钛三元离子共渗的方法对其进行表面改性处理。结果表明,在相同渗氮工艺下,海绵钛的加入,有效地提高了渗氮层的表面硬度;在520 ℃共渗8 h时,测得渗层硬度最高可达513 HV0.05。但是三元离子共渗降低了纯铁的磁性能,尤以低磁性能降低较多,稍低于GB/T 3656—2008要求,中磁性能与高磁性能仍满足标准要求。     

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。     

退氮处理对SDHS2模具钢渗氮层组织与性能的影响

采用光学显微镜和显微硬度仪对比研究了离子渗氮的SDHS2模具钢退氮处理前后渗氮层的组织和性能。结果表明:通过离子渗氮处理得到的渗层深度约230μm,渗层表面硬度达1 000 HV0. 3以上,渗层组织致密,与基体结合良好;分别经530和550℃退氮处理8、12、16 h后,渗氮层的硬度均大幅度降低。但随着渗氮时间的延长,渗层硬度随之提高;退氮温度的升高也会导致基体硬度的大幅度下降。综合比较得出,SDHS2模具钢退氮处理的最佳工艺为:退氮温度530℃、退氮时间8 h。在保证基体硬度满足要求的条件下,退氮处理可使表面硬度由处理前的1 000 HV0. 3以上降低至780 HV0. 3左右。     

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。     

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。     

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.     

奥氏体不锈钢稀土催渗离子渗氮工艺研究

对304、316L奥氏体不锈钢采用不同氮一氢比的气氛,在不同温度和不同保温时间进行了离子渗氮和稀土催渗离子渗氮。结果表明,经580℃在氮一氢比为1：3的气氛中稀土催渗离子渗氮9h,304和316L钢的渗层深度分别为0．12mm和0．112mm,表面硬度达1000HV0．1左右,与常规离子渗氮工艺相比,渗氮时间缩短了1h。     

添加微量硼对离子渗氮渗层组织性能的影响EI北大核心CSCD

以42CrMo钢为材料,探索添加微量硼对离子渗氮效率和渗层组织性能的影响。利用光学显微镜、X射线衍射仪(XRD)、显微硬度计、摩擦磨损测试仪等仪器对截面显微组织、物相、截面硬度、渗层韧性以及耐磨性等性能进行测试和分析。研究结果表明,离子共渗可显著提高渗氮效率,在相同离子渗氮工艺520℃保温6 h条件下,化合物层厚度随B添加量增加逐渐加厚,由常规离子渗氮处理后的18.78μm增加到29.44μm;同时硼氮离子共渗后在化合物层与扩散层相连处形成了锯齿状垂直楔入基体的硼铁化合物FeB和Fe_(2)B,达到增强渗层与基体结合力及提高渗层硬度的显著效果。随B添加量增加,试样表面硬度和有效硬化层深度都逐渐提高,表面硬度可由常规离子渗氮的750 HV_(0.05)提高至100 2 HV_(0.05);有效硬化层厚度由常规离子渗氮的265μm增加到355μm,相当于渗氮效率提高约35%。硼氮离子共渗处理后试样耐磨性和渗层韧性明显高于常规离子渗氮。     

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).     

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.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

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.