激光重熔处理对渗硼层脆性的影响

利用两种工艺方案对渗硼层进行了激光重熔处理，并通过声发射技术对表层脆性进行了定量测试。结果表明，激光重熔处理在不同程度上降低了渗硼层的脆性，相对脆性最大降低了71．3％。通过改变渗硼层的形貌和组织结构，消除FeB和渗层内的缺陷，改善界面结合强度和适当降低表层硬度从而使硼原子得到重新分布等方式均能降低表层脆性。     

激光处理技术对渗硼层组织与性能的影响

钢材表面经渗硼处理将会提高耐磨性,但同时也使脆性增大并产生剥落现象。采用激光技术通过改变硬化层结构,大幅度改善了表面性能。本文利用各种分析手段,系统地研究了45＃钢渗硼层显微组织特征及其变化规律.认为:(1)硬化层脆性化合物明显细化,(2)渗硼层出现了硬度低于硼化铁的组织以及,(3)显微组织在渗硼层的分布合理,导致硬度梯度平缓,是降低渗硼层脆性的主要原因。     

钢的硼—铬—稀土洪参层脆性行为研究

研究的钢的Ｂ－Ｃｒ－ＲＥ共渗层和渗硼层的脆性行为，表明，Ｂ－Ｃｒ－ＲＥ共渗层脆性明显低于渗硼层，且沿渗层不同深度的脆性分布呈“浴盆”型。进行适当渗后热处理可以降低渗层脆性。同时，地铬及稀土元素降低渗层脆性的机理作了探讨 。     

渗硼层表面脆性测量方法探讨

研究了显微硬度压痕法结合声发射技术在渗硼层表面进行脆性检测的可行性。结果表明，渗硼层表面测量的声发射能量累积计数值Ｅｎ与显微硬度压痕负荷Ｐ之间基本保持线性关系，可以用Ｅｎ－Ｐ直线方程的斜率Ｋ值定量表征渗硼层的脆性。渗硼层表面疏松较重，则给这种脆性检测方法带来一定影响。     

常压等离子多元共渗及其在气缸套上的应用

利用常压等离子体扫描金属表面，实现快速扫描多元共渗，用此技术对硼铸铁气缸套进行了Ｂ－Ｓｉ－Ｒｅ等多元共渗，通过电子探针，金相显微镜对多元共渗层的成分，组织进行了观察，利用显微硬度计测定了共渗层的硬度分布，９５型硼铸铁气缸套分别进行等离子多元共渗气缸套的耐磨性及配副性能优于激光处理，对比磨损试验结果表明，等离子体多元共渗气缸套的耐磨性及配副性能优于激光处理气缸套；缸套耐磨性提高７．７％，活塞环耐磨性     

钢的硼-铬-稀土共渗层脆性行为研究

研究了钢的B-Cr-RE共渗层和渗硼层的脆性行为,表明,B-Cr-RE共渗层脆性明显低于渗硼层,且沿渗层不同深度的脆性分布呈“浴盆”型.进行适当渗后热处理可以降低渗层脆性.同时,对铬及稀土元素降低渗层脆性的机理作了探讨.     

粉未渗硼中脆性影响因素研究

本文采用作者研制的三点弯曲小冲程脆性试验架对渗硼层脆性影响因素进行了研究,这些因素是渗硼剂中供硼剂和活性剂数量,渗硼温度,时间等,对试样表面光洁度及渗硼后冷却方式对渗硼层脆性的影响也做了研究。     

显微组织对冲蚀磨损的影响

研究了经不同热处理，特别是经渗硼＋激光共晶化处理的４５钢的４５钢的冲蚀磨损行为。结果表明，退火、正火和淬火回火系列的４５钢显示延性材料的冲蚀磨损特征，即最大部刨率发生在低攻角处，其中淬火＋高温回火试样在高角、低角冲蚀时都具有最低的磨损，渗硼和渗硼后激光共晶化的４５钢显示脆性材料的冲蚀磨损特征，即最大冲刨率发生在高攻角处，渗硼共晶层的冲蚀抗力明显优于渗硼层，且两者冲蚀抗力的差异在低攻角时更为显著。     

模具钢稀土硼铝共渗的研究和应用

研究了3Cr2W8V钢稀土硼铝共渗工艺，试验表明，共渗层具有高硬度（HV1800－2000），低脆性和良好的耐磨等性能，通过实际应用，取得良好效果。     

Cr及RE元素对硼化物层脆性的影响

对渗硼工艺形成的硼化物层脆性进行了分析,认识其剥落脆性是影响硼化物层脆性的主要因素,探讨了Ｃｒ及ＲＥ元素对降低硼化物脆性的机理,同时用ＥＥＴ理论对含Ｃｒ硼化物的价电子结构进行了研究。     

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。     

45钢激光渗硼后的显微组织及相结构分析

用扫描电子显微镜和Ｘ射线衍射仪对４５钢激光渗硼层的显微组织和相结构进行了分析，结果表明４５钢激光渗硼后，渗硼区的显微组织：表层为胞晶组织，次表层为树枝晶组织，再往里为共晶组织。渗硼区组织的相组成为α－Ｆｅ、ＦｅＢ、Ｆｅ２Ｂ、Ｆｅ３（Ｃ·Ｂ）及Ｂ４Ｃ相等。不同显微组织中各相所占比例不同，因而导致各区显微硬度不同。     

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.     

Localized boriding of low-carbon steel using a Nd:YAG laser

Localized boriding of low-carbon steel by the conventional technique requires tedious preboriding treatment and a long processing time. Laser boriding of low-carbon steel can be performed faster, and without any preboriding treatment. The feasibility of selective boriding of AISI 1018 steel using a NdYAG laser has been investigated. High hardness in the range 950–2200 H_v was obtained during laser boriding of AISI 1018 steel. The wide range of hardness is due to the variety of microstructures possible during laser boriding. Electron microprobe analysis showed that the highest hardness (2200 H_v) was due to the formation of FeB, and the lowest hardness was due to a mixture of Fe₂B and eutectic (_Fe+Fe₂B). The most desirable microstructure in laser boriding of AISI 1018 steel was found to be Fe₂B, which incorporates a combination of a high hardness, in the range of 1300–1700 H_v, and a compressive stress at the treated surface.     

Q235钢固体粉末渗硼及渗层生长动力学行为

各类材料渗硼工艺不同,硼的扩散也不同,其中有许多现象往往不能定量分析.采用固体粉末法对Q235钢进行了渗硼,得到的渗硼层为锯齿状,垂直于钢表面楔入基体.用sigma Plot 10.0软件对试验数据进行了分析和拟合,得出了渗硼层等厚度图,为制定渗硼工艺提供了依据:利用此图,既可以对设定的渗硼时间和温度预测渗硼层厚度,又可以用一定的固体渗硼厚度值确定渗硼时间和温度.通过动力学研究得到了渗层相组成为单一的Fe2B相硼,在不同温度下的扩散速率常数:K800℃=1.074×10-13m2/s,K850℃=1.622×10-13m2/s,K900℃=3.921×10-13m2/s,平均扩散激活能为134.473 kJ/mol.     

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.     

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.     

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...     

Effect of boronising on mechanical properties,wear and corrosion of N80 steel

Abstract

The effect of boronising on N80 steel tube was investigated by pack boriding. During the present investigation, microstructures of boride layer and substrate, hardness, mechanical properties, wear and corrosion were examined. In order to improve the tensile properties of the steel substrate after boronising, four different cooling methods were employed including annealing, air cooling, fan cooling and fan cooling with a graphite bar in the centre of boriding agent. Among these methods, the fan cooling with a graphite bar in the centre of the boriding agent makes the microstructure of ferrite and pearlite finest and the mechanical properties highest, in accordance with the mechanical properties required by API SPEC 5L. The borided N80 steel showed a better wear resistance at an applied load of 50 N with a sliding velocity of 0˙785 m s^–1, it also displayed a better corrosion resistance in both H₂SO₄ and HCl acid environments.