Study on the Components and Performance of GCr15 Bearing Steel Surface by Gas Multi-elements Penetrating

Gas multi-elements Penetration is a new surface hardening technology to improve the performance of the surface.In this paper, we focus on the study on the influence of multi-elements penetration on hardness of GCr15 bearing steel surface by C-N-O multi-elements penetrating treatment, and analyze the three elements, C, N and O in the surface with an EDX. Analysis of SEM images shows that there forms a penetrated layer 75 μ m or so in thickness over the surface, in which,0-30 μ m is the passivation layer, 30-60 μ m, the bright layer, and 60-75, the transition layer.     

钻机导轨40Cr钢喷丸强化与离子多元循环共渗复合工艺

以钻机导轨常用材料40Cr合金钢为研究对象,分析了喷丸强化+离子多元循环共渗复合工艺的作用机理。结果表明,复合工艺处理后的试样表面硬度为912 HV0.2,渗层深度为315 μm,优于单一离子多元共渗工艺。喷丸强化通过增加扩散通道,降低扩散能量的方式增大扩散系数;循环多元共渗使试样表面与扩散层的浓度梯度呈周期性变化,为相界面反应和内扩散提供驱动力。结果表明,喷丸强化+离子多元循环共渗工艺具有协同增强作用,能有效提升钻机导轨的表面性能。     

预渗处理对H13钢盐浴多元共渗行为的影响

以H13钢为基材,通过对比含预渗处理和不含预渗处理的稀土-N-C-S-V-Nb多元共渗复合表面强化工艺的处理结果,发现即使预渗温度和时间不同,也是经过预渗处理的渗层样品表层所含的碳、氮化物比未预渗的渗层样品多,其渗层厚度达100～120μm,组织致密且呈弥散分布,硬度比未预渗样品高,而且与基体的结合程度也得到很大改善....     

高速及重载道岔在线热处理钢轨压型跟端的感应热处理

为使高速及重载道岔AT钢尖轨跟端锻造热处理后组织与性能满足最新标准和线路使用要求,采用自主研发钢轨全断面感应加热+喷风冷却生产线,对高速及重载道岔60AT2-U71MnG及60AT1-U75V在线热处理钢轨压型跟端进行了热处理工艺试验,观察了硬化层的显微组织,检测了钢轨化学成分、硬化层深度、表面硬度、断面硬度、抗拉强度、伸长率及疲劳性能。结果表明,60AT2-60 kg/m(U71MnG材质)及60AT1-60 kg/m(U75V材质)在线热处理钢轨压型跟端经热处理后,钢轨轨头中心踏面硬化层深度不小于30 mm,显微组织为索氏体,表面硬度不小于320 HBW,抗拉强度不小于1200 MPa,伸长率不小于11%,表面硬度变化范围小于30 HBW,热影响软化区小于40 mm,弯曲疲劳强度达到200万次不断,各项技术指标均满足相关要求,可满足线路使用需求。     

H13热作模具钢RE-N-C-S-V-Nb多元共渗层的研究

对H13热作模具钢进行盐浴RE-N-C-S-V-Nb多元共渗,研究了渗层试样的组织、硬度及高温抗氧化性.结果表明:H13钢经盐浴RE-N-C-S-V-Nb共渗处理后,形成了厚约17 μm的表面渗层,渗层主要由含V,Nb和C,N的化合物组成,且组织细小而均匀,显微硬度呈梯度变化,高温抗氧化性能较好.     

空气-乙炔碳氮氧离子多元共渗工艺研究

用空气-乙炔混合气体作为气源,对40Cr钢进行了离子碳氮氧多元共渗;用光学金相显微镜、X射线衍射仪和显微硬度计,对渗层形貌、物相和显微硬度进行了分析检测。结果表明:乙炔浓度是影响性能的关键因素,它对硬度、物相起着决定性的作用。与常规离子渗氮相比,以空气-乙炔混合气体作为气源的碳氮氧离子多元共渗工艺操作简便,成本低廉。     

碳氮共渗-深层稀土硼碳氮共渗复合处理在20Cr钢耐火砖模具中的应用

在20Cr钢耐火砖模具表面进行了碳氮共渗-深层稀土硼碳氮共渗复合处理的生产试验研究.结果表明,复合处理硬化层的硬度梯度较平缓,稀土硼碳氮共渗层、碳氮共渗层以及基体形成了冶金结合,使模具寿命提高了80%以上.     

Surface nanostructures in commercial pure Ti induced by high energy shot peening

The high-energy shot peening (HESP) technique was used to obtain the surface nanocrystalline microstructure for a hcp metal titanium. XRD, SEM and TEM were applied to characterize the microstructure of the surface layer. Large amount of the deformation twins in the surface layer were observed by SEM in the specimens after HESP treatment in a shot-time, and the number of deformation twins both in a single plane and in intersecting planes increases with HESP time, until the twin character disappears completely in the top surface layer, which means that the severe plastic deformation(SPD) occurs on the surface. The XRD analysis results show that after HESP treatmen for 30 - 60 min the surface grain size decreases to nanoscale. According to the TEM images and corresponding diffraction patterns from SPD areas of the 120 min-treatment specimen, the measured grain size near the surface is about 20 - 30 nm. The grain size in deformation layer increases with the depth from the surface, and the nanostructured layer is about 20 μm in depth. Therefore, the surface nanocrystalline and a gradient microstructure from the surface to the matrix are obtained, which results in the micro-hardness decreasing from surface to the matrix gradually.     

Effect of binder saturation and powder layer thickness on the green strength of the binder jet 3D printing (BJ3DP) WC-12%Co powders

Printed parts displaying good green/handling strength are vital for the Binder Jet 3D Printing (BJ3DP) process to succeed in manufacturing complex parts with thin sections and tiny intricate features. A study was carried out to understand the effect of the binder saturation and powder layer thickness on green strength of the printed samples. The ability of using the green strength data of the samples to identify the optimum processing conditions for printing was examined. The strength of the parts were evaluated after printing at binder saturation levels of 45–75% and powder layer thickness of 50-70 μm. For any given powder layer thickness, the strength of the samples increased with increase in binder saturation. The samples printed at 60 and 75% saturation showed similar strengths at 50 and 60 μm layer thickness. However, the strength decreased with further increase in powder layer thickness to 70 μm. Doubling the binder set time and increasing the binder saturation options were evaluated to minimize the difference in the strength of the parts printed at 60 and 70 μm thickness. Increasing the binder saturation was found beneficial in minimizing the difference in the strength of the parts printed at 60 and 70 μm thickness compared to doubling the binder set time.     

喷丸工艺对TC4钛合金梯度纳米晶结构的作用规律

目的通过改变喷丸的压力或时间,在钛合金表面制备出剧烈塑性变形(SPD)层较厚、硬度较高的梯度纳米晶结构。方法改变喷丸压力(0.3~0.6 MPa)或喷丸时间(15~60 min),调控TC4钛合金表面梯度纳米晶结构的变形层厚度和纳米晶晶粒尺寸。利用金相显微镜观察塑性变形层截面的组织形貌,通过X射线衍射仪(XRD)和透射电子显微镜(TEM)确定喷丸表面纳米晶的晶粒尺寸,通过显微硬度计对塑性变形层的截面硬度进行研究。结果一定喷丸压力(0.6MPa)下,SPD层和总变形层厚度分别在喷丸25、30 min时达到饱和值78μm和143μm。一定喷丸时间(25 min)下,SPD层和总变形层的厚度随喷丸压力的增加而增厚,在0.4 MPa时达到饱和,分别为78μm和120μm。当SPD层厚度进入饱和阶段后,表层晶粒大小和硬度强化程度都趋于稳定;在0.6 MPa下,当表面α相细化至稳定阶段时,晶粒尺寸为30~90 nm,表面硬度提高约30%。结论喷丸SPD层及总变形层的厚度随喷丸时间的延长或喷丸压力的增大而增厚,当SPD层厚度趋于饱和后,表面晶粒尺寸和硬度强化程度都已饱和。     

H13钢碳、氮、氧、硫、硼五元共渗层的性能研究

研究了H13金刚经氮、碳、氧、硫、硼五元共渗后的性能。结果表明，由于多元共渗后层存在多种化合物，从而使H13钢的热稳定性、热疲劳抗力，耐磨性等得到明显改善，上述性能指标均比单一渗氮层高得多。     

Microstructure characteristics of as-surface nanocrystallized 1420 aluminum alloy by high-energy shot peening

A nanostructured surface layer was fabricated on 1420 aluminum alloy by high-energy shot peening.Microstructures were characterized by X-ray diffractometer (XRD), transmission electron microscope (TEM) and high-resolution electron microscope(HRTEM), and microhardness measurement was conducted along the depth from top surface layer to matrix of the sample peened for 30 rain. The results show that a nanocrystalline layer about 20μm in thickness is formed on the surface of the sample after high-energy shot peening, in which the grain size is changed from about 20 nm to 100 nm. In the surface layer of 20-50μm in depth, the microstructure consists of submicron grains. The surface nanocrystallization is accomplished by dislocation slip. The microhardness of the top surface nanostructured layer is enhanced obviously after high-energy shot peening(HESP) compared with that of the coarse-grained matrix.     

不同入射角弹丸强化残余应力场的数值模拟

目的通过建立有限元模型模拟研究弹丸入射角度对残余应力场和强化效果的影响。方法采用ABAQUS软件建立了单粒弹丸强化靶体的三维对称模型,对单个弹丸喷丸强化进行了数值模拟,模拟了50、75、100 m/s三种不同速度下,弹丸垂直入射作用在靶体上所产生的残余压应力场,以及30°、60°和90°三种不同入射角度下靶体上产生的残余应力场。结果不同速度下弹丸垂直入射作用在靶体上所产生的残余压应力场的模拟结果显示,随着弹丸速度的增加,靶材次表层的最大残余压应力以及压应力层深度增加。不同入射角度下靶体上产生的残余应力场深度和大小变化不相同,入射角为90°(垂直入射)时,所产生的残余压应力最大,入射角为60°时次之,入射角为30°时最小。结论模拟结果与实验结果的残余压应力最大值和曲线的变化趋势基本一致,吻合程度较高,说明所建的有限元模型可靠。在相同速度下,随着入射角度不断变大,所产生的最大残余压应力也不断增加,在垂直入射时达到最大值。     

表面纳米化对β型钛合金耐腐蚀性能的影响(英文)

采用表面机械研磨处理(SMAT)方法对医用β型TiNbZrFe合金表面处理60 min,研究表面纳米化对TiNbZrFe合金在生理环境下耐腐蚀性能的影响。采用TEM观察表层纳米晶微观结构特征,采用电化学方法研究表面为粗晶与纳米晶的TiNbZrFe合金在0.9%NaCl和0.2%NaF溶液环境下的电化学行为。结果表明:TiNbZrFe合金表面形成深度约30μm的纳米晶层,纳米晶尺寸为10~30 nm。在0.9%NaCl和0.2%NaF腐蚀环境下,与粗晶表面相比,表面为纳米晶的合金表现出较高的电阻、较正的自腐蚀电位以及较低的自腐蚀电流密度。合金耐腐蚀性能的提高主要归因于在纳米化的TiNbZrFe合金表面能够快速形成致密且稳定的钝化膜。     

18CrNiMo7-6钢渗碳淬火齿轮不同喷丸处理后的齿根表层应力分布

对模数20 mm的18CrNiMo7-6钢渗碳淬火齿轮经不同喷丸处理后的齿根表层应力分布进行测试,并与未喷丸时进行了对比。结果表明,在喷丸前后18CrNiMo7-6钢渗碳淬火齿轮齿根最表层均为压应力状态,从表至里均呈先升高后降低的变化趋势。未喷丸时最表层残余应力约为-75 MPa,最大残余应力出现在次表层110~120 μm处,约为-250 MPa;喷丸处理可使齿根表层残余压应力提高4~5倍,最表层残余应力在-350 MPa左右,最大残余应力出现在次表层90～110 μm处,为-900~-1000 MPa。     

Influence of Plasma Nitriding on the Microstructure, Wear, and Corrosion Properties of Quenched 30CrMnSiA Steel

The oil-quenched 30CrMnSiA steel specimens have been pulse plasma-nitrided for 4 h using a constant 25% N₂-75% H₂ gaseous mixture. Different nitriding temperatures varying from 400 to 560 °C have been used to investigate the effects of treatment temperature on the microstructure, microhardness, wear, and corrosion resistances of the surface layers of the nitrided specimens. The results show that significant surface-hardened layer consisting of compound and diffusion layers can be obtained when the oil-quenched steel (α′-Fe) are plasma-nitrided at these experimental conditions, and the compound layer mainly consists of ε-Fe_2-3N and γ′-Fe₄N phases. Lower temperature (400-500 °C) nitriding favors the formation of ε-Fe_2-3N phase in surface layer, while a monophase γ′-Fe₄N layer can be obtained when the nitriding is carried out at a higher temperature (560 °C). With increasing nitriding temperature, the compound layer thickness increases firstly from 2-3 μm (400 °C) to 8 μm (500 °C) and then decreases to 4.5 μm (560 °C). The surface roughness increases remarkably, and both the surface and inner microhardness of the nitrided samples decrease as increasing the temperature. The compact compound layers with more ε-Fe_2-3N phase can be obtained at lower temperature and have much higher wear and corrosion resistances than those compound layers formed employing 500-560 °C plasma nitriding.     

20CrMnTi钢压辊深层稀土硼碳氮共渗

对20CrMnTi钢深层稀土硼碳氮共渗工艺进行了研究，并对其共渗层的组织、硬度及耐磨性和耐腐蚀性能进行了测试与分析。结果表明，与碳氮共渗工艺相比，深层稀土硼碳氮共渗层的硬度、耐磨性和耐蚀性明显提高。将其应用于20CrMnTi钢粮机压辊，模具寿命提高了40％，取得了较好的经济效益。     

等离子共渗W-Mo-Y工艺及渗层组织的研究

采用辉光等离子渗金属技术对Q235钢进行W-Mo-Y三元共渗,探讨了极间距、气压、保温时间、温度对共渗层厚度的影响,并分析了共渗层的金相显微组织、合金元素分布及物相组成.结果表明:在试验涉及的条件下,以极间距25 mm,气压30 Pa,保温时间3 h,温度1000℃为最佳工艺参数;共渗层主要由Fe3Mo,Fe(Mo,W...     

20CrMnTi钢粮机压辊碳氮共渗的应用研究

对粮机压辊在材料与热处理工艺方面进行了改进，并采用金相显微镜、硬度计、电子天平等设备对共渗层进行了组织、硬度、耐腐蚀性分析。与38CrMoAl钢氮化处理相比，20CrMnTi钢碳氮共渗处理得到了硬度与层深的适当配合．取得了模具成本降低50％、经济效益提高70％的良好效果。     

Effect of gas composition on cementite decomposition and coke formation on iron

Cementite decomposition and coke formation in the metal dusting process of iron were investigated at 700 °C in CO-H₂-H₂O gas mixtures. The presence of graphite deposited on the surface initiates the decomposition of cementite into iron and graphite. The morphology of the reaction products varies with gas composition. For CO concentrations less than 5 vol%, particles of iron or even closed iron layers have been observed at the cementite/graphite interface. With increasing CO content the amount of iron in the interface decreases. At CO concentrations higher than 30 vol%, iron could not be detected at the interface by optical microscopy. Thermo-gravimetric analysis shows that the rate of carbon take-up increases with increasing CO concentration reaching a maximum at about 60-75 vol%.The morphologies of graphite in the coke layer can be identified as three types: porous graphite clusters with embedded iron-containing particles, compact bulk graphite with a uniform thickness and a columnar layered structure, and filamentous carbon with iron-containing phases at the tip or along its length. For gas mixtures with low CO concentrations, e.g. 5 vol%, porous graphite clusters are the main form of carbon although filamentous carbon can be seen at the early stage of reaction. With increasing CO concentrations to, e.g. 30 vol%, a compact bulk graphite is formed on the top of the surface. Under this compact graphite, there is an inner layer of graphite which is the combination of porous graphite clusters and filaments. These two layers of graphite are clearly distinguishable when CO content reaches more than 75 vol%. In this case, the main form of graphite in the inner layer is filamentous carbon. The compact graphite layer suffers a serious deformation and forms many cracks because of the growth of catalytic filamentous carbon underneath. These filaments grow outside from compact graphite crevices and finally cover the whole surface. The higher the CO content in the gas, the more the tendency of filamentous carbon formation. The interplay between morphologies of carbon formation and metal dusting has been discussed.