H13钢自保护膏剂稀土渗硼工艺优化

目前鲜见针对H13钢铁稀土渗硼的工艺优化研究。为此,采用自保护膏剂对H13钢进行稀土渗硼试验,运用正交试验法考察了渗硼时间、渗硼温度、稀土含量对渗层厚度、显微组织、显微硬度的影响,从而优选渗硼工艺。结果表明:渗层厚度随着稀土含量的增大先增加后减少,渗硼温度和渗硼时间的增加均可提高渗层厚度。由此得到最优的稀土渗硼工艺参数为:渗硼温度950℃、渗硼时间4 h、稀土含量4%,在此最优工艺下稀土渗硼层厚度达92.1μm,比无稀土渗硼提高约70%;其中,稀土渗硼的高硬度层(大于800 HV)厚度达75μm,比无稀土渗硼提高约1倍,并且显微组织更为致密均匀,渗硼层与基体结合更为紧密。     

熔盐电解法和固体粉末法在纯镍表面渗硼的对比研究

本工作分别采用熔盐电解法和固体粉末法对纯镍表面进行渗硼处理,以提高镍的表面硬度。熔盐电解法以硼砂(Na₂O₄B₇·10H₂O)作硼源,碳酸钠(Na₂CO₃)作支持电解质,电流密度为750 A/m²;固体粉末法采用碳化硼(B₄C)和氟硼酸钾(KBF₄)作为渗硼剂。利用扫描电镜(SEM)和能谱仪(EDS)分析渗硼试样的断面形貌和元素含量,利用X射线衍射仪(XRD)分析试样的物相。结果表明：采用熔盐电解法和固体粉末法在纯镍表面渗硼,均得到由Ni₂B和Ni₃B组成的渗层;熔盐电解法在电解温度为950℃、电解时间为4 h时渗层厚度约为184.35μm,渗层表面硬度值为1 755HK;固体粉末法在渗硼温度为950℃、渗硼时间为10 h时所得渗层厚度约为176.35μm,渗层的表面硬度值是1 526HK;镍经过渗硼后其表面硬度值有明显的增加,渗层厚度越大,表面硬...     

稀土对H13钢固体渗硼层高温摩擦磨损性能的影响

研究了稀土氯化物CeCl3添加量对H13钢固体渗硼层截面形貌、显微硬度、表面粗糙度以及相组成的影响,以及稀土催渗辅助渗硼H13钢的高温摩擦磨损性能。结果表明:添加2.5%和5%的稀土显著提高渗硼层厚度、显微硬度与致密性,但是表面粗糙度略有提高;10%稀土渗硼试样的渗层最厚,但是其显微硬度、致密性明显下降,表面粗糙度提高;稀土辅助渗硼层中除Fe2B相外还出现了(Fe,Cr)2B相;与不加稀土渗硼试样相比,5%稀土渗硼试样的渗层磨穿时间约增加一倍,磨损率降低21%;5%稀土渗硼试样磨损率比未渗硼H13钢降低了61%,并且也低于10%稀土渗硼试样。因此,加入5%稀土催渗辅助渗硼H13钢的高温耐磨损性能较优。     

12Cr13马氏体不锈钢B/C化学热处理的研究

研究了固体硼碳共渗及复合渗技术工艺参数对12Cr13马氏体不锈钢的组织和性能的影响。共渗方面对12Cr13钢进行不同硼碳比例的固体硼碳共渗热处理;复合渗方面对12Cr13马氏体不锈钢先进行固体渗碳,然后再进行渗硼处理,得出最优的复合渗参数。对最优参数下的共渗及复合渗12Cr13马氏体不锈钢试样进行显微硬度、XRD物相结构、电化学下耐腐蚀和摩擦磨损性能检测分析。结果表明：共渗温度950℃、共渗6 h条件下,硼碳共渗最优渗剂硼碳比为6∶4;化学渗6 h条件下,硼碳复合渗最优参数为950℃渗碳,950℃渗硼;硼碳共渗和复合渗试件经过最终热处理(淬火+低温回火)后,表层组织硬度最高可达1 507.3 HV_{0.98 N},心部硬度为420.6 HV_{0.98 N},最优参数下硼碳共渗及复合渗渗层厚度分别为976μm和1 125μm;电化学测试表明硼碳共渗和硼碳复合渗处理后材料的耐蚀性有所提高,共渗腐蚀电位为-0.578 V,复合渗为-0.582 V。磨损试验显示硼碳共渗和硼碳复合渗后经化学热处理可以显著提高12Cr13马氏体不锈钢的耐磨性能。     

H13钢双保温固体渗硼高温磨损机理

研究了H13钢高能喷丸辅助双保温固体渗硼试样和未渗硼试样的高温摩擦磨损性能,并探讨了磨损机理。结果表明,高能喷丸辅助双保温固体渗硼后的试样得到Fe2B单相渗硼层,高能喷丸能显著提高固体渗硼效率;渗硼试样的高温磨损率比未渗硼试样降低了30%,表明渗硼提高了H13钢的高温耐磨损性能。渗硼和未渗硼试样高温摩擦磨损后磨损表面均形成了氧化层,氧化物为Fe2O3。渗硼层在高温下具有较高的硬度及良好的抗氧化性,因此渗硼试样的高温磨损机理主要是渗硼层的疲劳剥落和氧化磨损,而未渗硼试样的高温磨损机理主要为氧化磨损和磨粒磨损协同机制。     

直流电场作用下的快速粉末渗硅工艺

为了探讨施加直流电场对固体粉末渗硅渗速的影响,以20钢为基材,通过在渗硅介质与被改性样品间施加直流电场,研究快速粉末渗硅的合适工艺条件,并研究该工艺获得的渗层性能。结果表明:直流电场可降低粉末渗硅温度,显著提高渗硅速度;可使常规粉末渗硅温度从1 050℃以上降低到750℃;加热温度为800℃,直流电流6 A时,20钢的渗硅层厚约85μm;直流电场条件下获得的渗硅层主要由Fe5Si3相组成,在700℃具有良好的抗氧化性能。     

双辉低温(560℃)等离子渗铬的工艺研究

采用离子氮化 双辉等离子渗铬的复合工艺(首先对T10钢进行550℃x8h离子氮化,再进行560℃双辉等离子渗铬,渗铬完成后试样随炉冷却),研究了源极电压、阴极电压、极间距、工作气压、预氮化保温时间、渗铬保温时间等工艺参数对双辉等离子渗铬的影响,得出了本工艺条件下的最佳工艺参数.结果表明,在8h预氮化极间距50～60mm,阴极电压-275～325V、源极电压-750～-850V、渗铬气压25～35Pa的工艺条件下,渗层厚度约30μm,沉积层铬浓度达55%以上,扩散层铬浓度呈梯度分布;渗层由沉积层 扩散层组成,沉积层组织致密,与基体结合紧密,扩散层晶粒细小,碳化物弥散,不改变试样原始的基体组织;经X射线衍射分析,表层物相由Fe-Cr、CrN、Cr7C3、Cr23C6等组成,表面硬度达1000～1250HV,且呈梯度分布.     

氧气在 PVDF 片材中扩散的分子动力学模拟

目的研究气体在PVDF片材中的扩散。方法采用分子动力学模拟方法研究了氧气在其片材中的扩散行为,得到氧气在PVDF片材中的扩散系数,并讨论了时间、聚合度、温度及残余压力对扩散系数的影响。结果模拟时间太短对模拟结果不利,应以大于1000 fs为宜。当聚合度由400增加到800时,扩散系数由4.77×10-6cm2/s下降到1.78×10-6cm2/s;当温度从298 K提高到303 K时,扩散系数由1.06×10-6cm2/s增加到1.42×10-6cm2/s;当残余压力由60 kPa增大到100 kPa时,扩散系数由7.07×10-6cm2/s下降到3.06×10-6cm2/s。结论氧气在PVDF片层中的扩散系数随聚合度和残余压力的增大而变小,随温度的提高而变大。     

Ti/Cu扩散溶解层的组织结构和形成规律

采用镶嵌式扩散偶,在不同退火处理条件下,对Ti/Cu扩散溶解层进行了研究.利用扫描电子显微镜和电子探针显微分析仪观察和分析了扩散溶解层的组织结构和形成规律.结果表明,随着加热温度的升高和保温时间的延长,在Ti/Cu界面处会形成相界面依附于扩散偶组元Cu丝、形态各不相同、层数以及总层与单层厚度逐渐增加的"环状"扩散溶解层;当进行700℃、100小时真空退火热处理时,扩散溶解层厚度为93μm;其中一层呈"锯齿状"朝向Cu,分别有两层处于同一个层区域内,并以"竹笋状"方式互相交错重叠;结构为Cu/Cu4Ti/Cu2Ti/Cu3Ti2/Cu4Ti3/CuTi/CuTi2/Ti,而且其结构与Cu-Ti相图上各个相的左右排列顺序一致.不同的扩散温度和时间,Ti/Cu相界面处将几乎同时结晶出不同层数、厚度和结构的扩散溶解层.     

槽电压对纯铁表面液相等离子体电解硼碳氮三元共渗层摩擦磨损性能的影响

利用液相等离子体电解渗技术分别在340,360V和380V槽电压下对纯铁进行硼碳氮三元共渗(PEB/C/N)表面处理。分析纯铁表面PEB/C/N共渗层的形貌、成分、相组成和显微硬度分布。采用球-盘摩擦磨损仪评估槽电压对渗层摩擦磨损性能的影响,并分析渗层与ZrO_2球对磨时磨损机理。纯铁表面的PEB/C/N三元共渗层厚度随着放电电压升高而增大,最高硬度也相应增加。380V处理1h后硼碳氮三元共渗层中渗硼层和过渡层厚度分别达到26μm和34μm,渗层最高硬度可以达到2318HV。硼碳氮三元共渗层的磨损率仅为纯铁基体的1/10。硼碳氮共渗处理大幅度降低纯铁的摩擦因数和磨损率,但不同槽电压下制备的PEB/C/N共渗层的摩擦因数和磨损率变化较小。     

Influence of Surface Nano-structured Treatment on Pack Boriding of H13 Steel

In order to lower the boriding temperature of hot work steel H13, method of surface mechanical attrition treatment （SMAT）, which can make the grain size of the surface reach nano-scale, was used before pack boriding. The growth of the boride layer was studied in a function of boriding temperature and time. By TEM （transmission electron microscopy）, SEM （scanning electron microscopy）, XRD （x-ray diffraction） and microhardness tests, the grain size, thermal stability of the nano-structured （NS） surface and the thickness,appearance, phases of the surface boride layer were studied. Kinetic of boriding was compared between untreated samples and treated samples. Results showed that after SMAT, the boride layer was thicker and the hardness gradient was smoother. Furthermore, after boriding at a low temperature of 700℃ for 8 h, a boride layer of about 5 μm formed on the NS surface. This layer was toothlike and wedged into the substrate, which made the surface layer combine well with the substrate. The phase of the boride layer was Fe2B. Research on boriding kinetics indicated that the activation energy was decreased for the treated samples.     

Boriding kinetics of H13 steel

It is known that boriding has been employed to increase the service life of parts such as orifices; ingot molds, and dies for hot forming made of AISI H13 steel. In this study, case properties and kinetics of borided AISI H13 steel have been investigated by conducting a series of experiments in Ekabor-I powders at the process temperature of 1073, 1173 and 1273 K for periods of 1-5 h. The presence of borides FeB and Fe₂B of steel substrate was confirmed by optical microscopy and scanning electron microscopy (SEM). The results of this study indicated that the morphology of the boride layer has a smooth and compact morphology, and its hardness was found to be in the range of 1650-2000 HV. Transition zone observed between the hard boride coating and the matrix was relatively softer than the substrate. The kinetics of boriding shows a parabolic relationship between layer thickness and process time, and the calculated activation energy for the process is 186.2 kJ/mol. Moreover, boriding parameter BOP, which is only a function of boride layer thickness and activation energy, has been suggested for the prediction of layer thickness in boriding of AISI H13. There is a reasonable correlation between the progress of boride layer thickness and proposed time-temperature-compensated parameter. Similar findings have been found when it is applied to another steels including tool and low alloy steels, as well as Armco iron.     

渗硼层脆性及其控制措施

分析了产生渗硼层脆性的本质属性和工艺因素两个方面的原因，提出了控制渗硼层脆性的4种途径：多元渗硼，改进渗硼工艺方法，控制渗层相的组成及其结构，渗硼层的再处理，其中以多元稀土共渗，超塑渗硼，激光渗硼和渗硼层的激光重熔技术等工艺方法控制脆性效果显著，同时，对几种实用的渗硼层脆性测试方法进行了对比和评述，为进一步发挥产品渗硼后的性能提供参考。     

A comparative study of borided pure niobium, tungsten and chromium

Pure niobium (Nb), tungsten (W) and chromium (Cr) were boronized at 940 °C for 2, 4 and 8 h. The borided samples were characterized by X-ray diffraction, Scanning electron microscope and microhardness tests. Tribological investigation was conducted. X-ray study showed the presence of NbB₂, WB, and CrB. The hardnesses of boride layers formed on the pure Nb, W and Cr were 2500, 2500 and 1700 HV, respectively, whereas the hardnesses of the pure Nb, pure W and pure Cr were 110, 445 and 115 HV, respectively. Nb boride layers ranged in thickness from 8 to 22 μm, whereas W boride layers ranged in thickness from 10 to 42 μm, and the thickness of Cr boride layer varied from 4 to 12 μm with boronizing time. The boriding of W resulted in thicker boride layer compared to the boriding of Nb and Cr at given time. The frictional behaviour and wear mechanicms differ in modes and scales.     

Research on Properties of Fe-Based Powder Metallurgy Material Strengthened by Boriding

Strength of Materials - The pack boriding process of Fe-based powder compact was carried out at 850 to 1050°C for 3 to 10 h. The microstructure and the thickness of the boride layer were...     

钛合金表面阳极微弧等离子体渗硼层的研究

采用阳极微弧等离子体技术研究了钛合金表面渗硼层的微观组织和性能。通过光学显微镜、扫描电镜(SEM)、X射线衍射仪(XRD)、能谱仪(EDS)表征分析了渗硼层的表面和截面的微观组织、形貌、相结构、渗层元素分布。借助摩擦磨损试验机测试了渗硼层的耐磨性,运用电化学工作站对渗硼后的TC4材料进行了耐腐蚀性测试。结果表明,钛合金表面阳极微弧等离子体渗硼技术制备的渗硼层连续致密。渗硼层主要由金属间化合物TiB2和TiB组成,其与氧化层共同作用,能显著提高钛合金表面的耐磨性。渗硼后的TC4钛合金耐腐蚀性较基体有所降低。表面阳极微弧等离子体技术是一种新型的钛合金表面改性方法。     

PZT95／5型铁电陶瓷复合烧结研究

本文研究了ＰＺＴ９５／５型铁电陶瓷的复合（层叠）烧结，Ｎｂ２Ｏ５添加剂含量不同的两组份层叠形成的复合之间存在一个扩散界在层，组成间Ｎｂ含量浓度梯度差值越大，扩散界面层厚度越大。理论分析表明，烧结工艺对扩散界面层厚度一的影响，烧结温度赵高，保温时间越长，扩散界面怪厚度越大。     

Influence of different electron beam surface pre-treatments on the results of subsequent boriding-part I

Boriding produce thick hard layers on cast iron components, which can improve their wear and corrosion behaviour. However, this potential cannot be fully exploited by a simple boriding due to the material specific presence of graphite. In that context, this paper presents results of two fundamentally different electron beam liquid surface treatments (remelting, cladding with nickel-based additive) and their possibilities and limitations regarding subsequent boriding. The boriding behaviour under conventional high temperatures (760 °C–860 °C), and experiments on low-temperature boriding (600 °C–700 °C) were investigated. Under identical treatment conditions, the compound layer thicknesses generated on the unalloyed surfaces (remelting) were approx. 50 %–75 % greater than those of the alloyed surfaces (cladding). A two-layered boride layer structure were generated, though with different phase compositions. Nevertheless, the hardness of all borided layers were comparable. Surface hardness measurements revealed that the supporting effect of substrates plays a decisive role up to a boride layer thickness of approx. 57 μm. In this layer-thickness range, the compound hardness of the alloyed substrates is higher than that of the unalloyed substrates. This knowledge should prove decisive for the selection of layer composites for corrosive and/or tribologically stressed components.     

Effects of rare earth additions during surface boriding on microstructure and properties of titanium alloy TC21

Abstract

In the present paper, the effects of rare earth (RE) additions to the solid state boriding of titanium alloy TC21 have been studied. The microstructural evolution and phase transformations of the borided layers were examined using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction. Moreover, the microhardness for the borided layer was also determined by Vickers hardness test. The results showed that the addition of a small amount of RE elements in the boriding process can lead to an increased boron concentration in the surface layer coupled with the improved surface hardness and coating layer thickness. Furthermore, the presence of trace quantities of RE oxide (Ce₂O₃) in boride layers indicated that the RE elements as catalysts could not only influence but also accelerate boriding process.     

Electrochemical boriding and characterization of AISI D2 tool steel

D2 is an air-hardening tool steel and due to its high chromium content provides very good protection against wear and oxidation, especially at elevated temperatures. Boriding of D2 steel can further enhance its surface mechanical and tribological properties. Unfortunately, it has been very difficult to achieve a very dense and uniformly thick boride layers on D2 steel using traditional boriding processes. In an attempt to overcome such a deficiency, we explored the suitability and potential usefulness of electrochemical boriding for achieving thick and hard boride layers on this tool steel in a molten borax electrolyte at 850, 900, 950 and 1000 °C for durations ranging from 15 min to 1 h. The microstructural characterization and phase analysis of the resultant boride layers were performed using optical, scanning electron microscopy and X-ray diffraction methods. Our studies have confirmed that a single phase Fe₂B layer or a composite layer consisting of FeB + Fe₂B is feasible on the surface of D2 steel depending on the length of boriding time. The boride layers formed after shorter durations (i.e., 15 min) mainly consisted of Fe₂B phase and was about 30 μm thick. The thickness of the layer formed in 60 min was about 60 μm and composed mainly of FeB and Fe₂B. The cross sectional micro-hardness values of the boride layers varied between 14 and 22 GPa, depending on the phase composition.