20钢渗硼过程中硼化物形核和生长的TEM观察及室温形变的影响SCIEI

本文采用单向减薄制样法在透射电镜下直接观察了20钢渗硼初期硼化物的形核和生长特性及室温形变的影响。X射线及电子探针分析结果表明:渗硼初期试样表层仅有Fe_2B形成;表层硼原子浓度与形变量之间具有单调增长的关系;偏聚于位错胞壁之中的硼原子阻碍了形变组织的恢复和再结晶,加速了硼化物的形核和长大。     

渗硼层生长的控制因素及其动力学过程分析SCIEI

本文采用透射电镜观察了渗硼初期硼化物的形核特征及不同阶段硼化物晶体内部显微组织的差异,提出了试样表层硼化物晶核密度是渗硼层生长的控制因素。渗硼的动力学过程可分为两个阶段:在第一阶段,渗层厚度随时间的变化呈抛物线规律;当渗层前沿的压应力超过某临界值时,便在硼化物晶体中诱发出层错,加速了硼原子的扩散和渗层的生长,使渗硼过程进入第二阶段,此时层厚和保温时间之间的关系,偏离抛物线规律而呈近似的直线关系。     

A study of the behavior of boron diffusion in plain carbon steels

Boronizing treatment of ferrous materials has been widely employed by industry as a surface-strengthening technology for inhibition of corrosion, wear and erosion. Pack boronization using a pack composition that produces a graded boride microstructure has been studied using AISI 1018 and 1045 steels. Carbon in these alloys creates a resistance to boron diffusion because a carbon-enriched zone forms in front of the boride layen The carbon concentration at the boride/pearlite interface was found to be as high as 3.0% in AISI 1045 steel. No significant layer phenomena could be distinguished inside the boron layer using the pack composition developed during this research. This result is significant because a graded microstructure with a continuous variation of the boron composition has been produced. Evidence developed during this study suggests that the boride layer consists of a mixture of FeB, Fe₂B, and FeB_x, which is probably FeB₁₉. Analysis determined a measure of the resistance of carbon to boron diffusion at the boride/pearlite interface.     

Some Properties of a Boronised Spheroidal-graphite Cast Iron

Abstract

Boronising treatment of spheroidal graphite cast iron was investigated by means of electrolysis in a molten salt mainly consisting of B₂O₃, K₂O and Na₂O at various temperatures and over different periods of time. The microhardness and the thickness of boride layers were measured and the distributions of B, Si and C on the surface of specimens were observed by an X-ray microanalyser. Microscopic examination and the results of X-ray microanalysis showed that the boride layer consisted of two layers; an outer FeB layer and an inner Fe₂B layer. The microhardness of these boride layers were approximately HVN 1500–1800. The thickness of the boride layer increased in proportion to the square root of treatment time at constant temperature. The activation energy for diffusion of boron in the specimen was 19.5 kcal/mol, as obtained from the slope of Arrhenius plots.

A Si rich layer was formed in a region outside the boride layer in specimens after boronising. Moreover, graphite formation was observed in the Si rich layer in specimens boronised at austenitising temperatures for a prolonged time. Graphite formation in the Si rich layer can be considered to be a consequence of the precipitation of carbon, during the cooling process after boronising, which diffused from spheroidal graphite to the austenite matrix at the boronising temperature. Large amounts of graphite formed in the Si-rich layer resulted in a crack passing through these graphite particles.     

白层形态及形成机制

用透射电镜研究了冲击磨损所形成白层的组织形态，试验结果表明，钢中白层的亚结构具有多种形态，由表及里依次为细条状，缠结胞状，多边网状和等轴状位错组态，它们均由不均匀变形造成，观察结果进一步证实了白层的形变机制。     

WC/钢复合材料渗硼中WC颗粒对硼化物生长的影响

采用粉末渗硼法,对三种WC含量不同的WC/钢复合材料进行渗硼处理.利用SEM、XRD及自制的黑白图片伪彩色处理仪等方法对渗硼层的组织结构、硬度分布、渗硼层厚度及渗硼层内裂纹萌生进行研究,重点分析了WC含量及分布状况对硼化物生长的影响.结果表明：进行渗硼后,材料表面可获得高硬度FeB＋Fe2B的渗硼层,且随WC含量的增加,Fe2B含量相对增加.在渗硼过程中,WC颗粒对硼化物的生长起阻碍作用,而且含量愈多,阻碍作用愈大,渗硼层愈浅.当WC颗粒的分布方向与渗硼方向平行时,对硼化物生长的阻碍作用最小,渗硼层厚且致密,且在冷却时不易产生裂纹;当WC颗粒的分布方向与渗硼方向垂直时,对硼化物的生长阻碍作用最大,获得的渗硼层较浅,并且在渗层中出现明显的疏松区;当WC粒子呈无序分布,对硼化物的生长阻碍作用介于上面两者之间.硼化物生长时,遇到大颗粒WC其尖端变钝并停止生长;遇到小颗粒WC可以＂吞食＂.     

La2O3包埋渗硼TB2钛合金的腐蚀与磨损性能

为了改善TB2合金的表面性能,采用4％La2O3(质量分数)包埋渗硼法对TB2合金进行1100℃,20 h渗硼处理,研究TB2钛合金的渗硼层组成与厚度以及腐蚀与磨损性能.结果表明,La2O3在渗硼过程中促进硼化物层的生长,提高其连续性和致密性,TiB晶须长度从16.80增至21.84μm.这是因为La2O3能与B反应生...     

Kinetics of plasma paste boronized AISI 8620 steel in borax paste mixtures

In the present study, AISI 8620 steel was plasma paste boronized by using various borax paste mixtures. The plasma paste boronizing process was carried out in a dc plasma system at a temperature of 973, 1023 and 1073 K for 2, 5 and 7 h respectively in a gas mixture of 70% H₂-30% Ar under a constant pressure of 10 mbar. The properties of the boride layer were evaluated by optical microscopy, X-ray diffraction, the micro-Vickers hardness tester and the growth kinetics of the boride layers. The thickness of the boride layers varied from 14 to 91 μm depending on the boronizing time and temperature. X-ray diffraction analysis of boride layers on the surface of the steel revealed the formation of FeB and Fe₂B phases. Depending on the temperature and layer thickness, the activation energies of boron in steel were found to be 99.773 kJ/mol for 100% borax paste.     

Investigation of kinetics of borided ductile and lamellar graphite cast iron

In this study, kinetics of borided ductile iron and lameller graphite grey cast iron were investigated by processing boronizing treatment (was carried out in Ekobor-II powders). The process temperatures and durations respectively 1123, 1173, 1223 K for 2, 4 and 6 hours, with pack boronizing method and under atmospheric pressure in electrical resistance furnace. Changing of borided layer properties was investigated by using optical and scanning electron microscopy, X-ray diffraction and micro-Vickers hardness testers. The growth kinetics of the boride layers forming and thickness of boride layer were computed for both cast iron. The main phases for two processes Fe₂B and FeB were defined on the surface.     

Influence of process duration on structure and chemistry of borided low carbon steel

In this study, we employed an ultra-fast boriding technique to grow hard boride layers on low carbon steel substrates using an induction furnace at 900 °C. The technique utilizes an electrochemical cell in which it is possible to achieve very thick (i.e., about 90 μm thick) boride layers in about 30 min. The effects of process duration on boride layer thickness, composition, and structural morphology were investigated using microscopic and X-ray diffraction (XRD) methods. We also developed an empirical equation for the growth rate of boride layers. XRD results revealed two principal boride phases: FeB and Fe₂B thickness of which was very dependent on the process duration. For example, Fe₂B phase was more dominant during shorter boriding times (i.e., up to 15 min.) but FeB became much more pronounced at much longer durations. The growth rate of total boride layer was nearly linear up to 30 min of treatment. However during much longer process duration, the growth rate assumed a somewhat parabolic character that could be expressed as d = 1.4904 (t)^0.5 + 11.712), where d (in μm) is the growth rate, t (in s) is duration. The mechanical characterization of the borided surfaces in plane and in cross-sections has confirmed hardness values as high 19 GPa at or near the borided surface (where FeB phase is present). However, the hardness gradually decreased to 14 to 16 GPa levels in the region where Fe₂B phase was found.     

Characterization of borided pure molybdenum under controlled atmosphere

In this study, the structural characterization and boriding kinetics of the molybdenum borides formed on the surface of borided pure molybdenum (Mo) have been investigated. Boronizing was carried out in solid medium with boron component forming Ekabor ® 2 (90% SiC, 5% KBF₄, 5%B₄C) powders at 1273 K, 1373 K for 2, 4, 6, 8 hours under a controlled atmosphere containing argon gas flow. The boride layer was characterized by the scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Energy dispersive spectroscopy (EDS) and Vickers microhardness tester. X-ray diffraction analysis showed that the boride layers on molybdenum consisted of MoB and Mo₂B phases. However, the MoB phase was observed at certain boriding temperature and boriding times. The thickness of boronized layers almost ranged from 12 to 42.5 μm with boriding time. A parabolic relationship was observed between boride layer thickness and boriding time. The growth rate constant and activation energy for the boride layer were calculated. The hardness of borides compounds formed on the surface of molybdenum ranged from 925 to 1150 HV_0.05, whereas the hardness of the untreated molybdenum sample was 258 HV_0.05.     

Fracture Toughness of Thick Boride Layers Estimated by the Cross-Sectioned Scratch Test

New results about the fracture toughness (K_c) of thick boride layers estimated by the cross-sectioned scratch test are presented in this study. The FeB-Fe₂B layers developed at the surface of borided AISI 1018 and AISI 1045 steels and the Fe₂B layer formed on the borided AISI 1045 steel exposed to a diffusion annealing process (DAP) were used for this purpose. The cross-sectioned scratch tests were performed with a Vickers diamond stylus drawn across the thick boride layer under a constant load to produce a half-cone-shaped fracture near to the top surface of the borided steels. The height of the half-cone-shaped fracture as a function of the cross-sectioned scratch loads was used to determine the fracture toughness of the FeB and Fe₂B layers. The results showed a fracture resistance of \(\sim2.8\,{\text{MPa}}\sqrt m\) for the FeB layer formed at the surface of borided AISI 1045 steel. Likewise, the effect of the DAP on the surface of the borided AISI 1045 steel promoted the formation of an exclusively Fe₂B layer, with an increase in the fracture toughness of the whole boride layer around \(5\,{\text{MPa}}\sqrt m\). Finally, the principle of the technique can be used to minimize the influence of the anisotropic properties on the fracture toughness along the depth of boride layers.     

Cu-Ni合金内硼化及其动力学的研究

在提出了内硼化的概念之后，对三种含镍量不同的铜镍合金进行了内硼化处理。通过层深测量、Ｘ射线衍射分析、电子探针成分测定，分析了内硼化的动力学，并对硼在内硼化过程中的渗透率进行了计算。     

硼化物抑制石墨电极氧化研究

采用硼化物溶液浸渍石墨电极,测试不同浸渍量的试样在模拟炉中氧化失重率,物理性 能及表面形态,结果表明,硼化物在高温状下能在石墨电极表面形成连续防氧化保护膜填塞表面孔隙, 延缓或抑制石墨电极氧化,可使其消耗降低１５％左右。     

Investigation of corrosion behaviors at different solutions of boronized AISI 316L stainless steel

In this study, corrosion behaviors of boronized and non-boronized AISI 316L stainless steel (AISI 316L SS) were investigated with Tafel extrapolation and linear polarization methods in different solutions (1 mol dm^?3 HCl, 1 mol dm^?3 NaOH and 0.9% NaCl) and in different immersion times. AISI 316L SS were boronized by using pack boronizing method for 2 and 6 hours at 800 and 900°C within commercial Ekabor®-2 powder. Surface morphologies and phase analyses of boride layers on the surface of AISI 316L SS were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis. SEM-EDS analyses show that boride layer on AISI 316L SS surface had a flat and smooth morphology. It was detected by XRD analyses that boride layer contained FeB, Fe₂B, CrB, Cr₂B, NiB and Ni₂B phases. Boride layer thickness increases with increased boronizing temperature and time. The corrosion experiments show that boride layer significantly increased the corrosion resistance of the AISI 316L SS in 1 mol dm^?3 HCl solution. While no positive effect of the boride layer was observed in the other solutions the corrosion resistance of the borid layer on AISI 316L SS was increased in all solution with the increase of the waiting periods.     

硼离子注入对多晶Ni力学性能及微观结构的影响

用能量为50keV,剂量为3×10~(17)ions/cm_2的B~+注入多晶Ni,通过力学性能实验研究了多晶Ni注入前后表面硬度和疲劳性能的变化,以及多晶Ni表面层注入和疲劳前后化学成分、滑移特征、裂纹萌生、断裂方式和微观结构的变化。结果表明,B~+注入多晶Ni后,表面区域形成一个不同组织结构的由Ni-B非晶、Ni_3B和Ni_4B_3第二相以及辐照损伤组成的多层次的注入层,提高了多晶Ni的表面硬度,并使其疲劳极限提高16％。探讨了B~+注入影响多晶Ni疲劳极限的几种可能机制。     

Investigation of Boronizing Kinetics of AISI 51100 Steel

In this study, some mechanical properties of borided AISI 51100 steel with high C concentration were investigated. Boronizing heat treatment was carried out in solid medium consisting of Ekabor-II at 850, 900, and 950 °C for 2, 4, 6, and 8 h. Morphology and mechanical properties of boride layer, and the effect of chemical composition on properties and kinetics of borides were investigated. The results of this study indicated that the morphology of the boride layer has a saw-tooth nature, and its hardness is over 1500 HV. Depending on process time and temperature, the depth of boride layer ranged from 30 to 106 μm. Optical and SEM studies and XRD analysis revealed that borides formed on the surface of steel substrates have dominantly single Fe₂B boride phase in addition to small amount of Cr₂B.     

电渣熔铸钢结硬质合金渗硼初探

采用粉末渗硼法对电渣熔铸钢结硬质合金进行渗硼处理,利用光学显微镜对所获渗硼层的显微组织结构进行观察,用X射线衍射仪对渗硼层相结构进行分析,用显微硬度计对渗硼层硬度分布及渗硼层厚度进行了测量,研究了不同处理时间对硼化物生长的影响。结果表明:电渣熔铸钢结硬质合金具有良好的渗硼性能,渗硼后,合金表面可获得含有FeB+Fe2B的高硬度渗硼层,且随渗硼处理的时间延长,渗硼层厚度和表面硬度也随之增加,FeB含量也增加,在渗硼过程中,WC颗粒对硼化物的生长起阻碍作用,并且含量愈多,阻碍作用就愈明显,WC的形态对硼化物的生长影响较大,块状和树枝状的WC使渗硼后所获得的渗硼层浅而疏松。     

CrMnB堆焊合金抗空蚀和冲刷磨损性能的研究

研究了CrMnB堆焊合金的抗空蚀和冲刷磨损性能，结果表明，该堆焊合金的抗空蚀和冲刷磨损性能优于0Cr13Ni5Mo马氏体不锈钢，其原因是具有亚稳奥氏体和硼化物共晶组织的CrMnB堆焊合金，在冲击力的作用上，亚稳奥氏体相转变成了马氏体，提高了堆焊合金表面的硬度和强度并吸收了冲击能，同时沿奥氏体边界分布的高硬度的硼化物共晶组织，构成了耐磨“骨架”。     

Hard boride coating on iron aluminide (FeAl)

The mechanical properties of borided iron aluminide (FeAl) were investigated. Boronizing was carried out in a solid medium consisting of Ekabor powders at 940 °C for 2, 4 and 8 h. The formation of FeB on the surface of FeAl was confirmed by XRD analysis. Metallographic studies revealed an almost saw-tooth-like and compact boride layer on the FeAl. The thickness of boride layer ranged from 15 to 32 µm with standard deviation. The hardness of borided specimens decreased with the distance from the surface to the interior of the FeAl. The hardness of the boride on the FeAl ranged from 1362 to 1572 1572 HV while the hardness of the FeAl ranged from 374 to 436 436 HV. Radio Frequency-Glow Discharge Optical Emission Spectroscopy (RF-GDOES) allows the simultaneous measurement of the bulk composition and the depth profiles of all of the elements of interest.