共查询到20条相似文献,搜索用时 281 毫秒
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常压等离子束扫描表面多元共渗研究 总被引:2,自引:0,他引:2
用高参等离子束在常压下快速扫描涂敷合金渗剂的45^#钢管内表面,可实现多元共渗及自激冷淬火,获得多元共渗及淬火硬化层。用电子探针和透射电镜对硬化层的成分和组织结构进行分析,结果表明,渗剂中所含硼、硅、铈三种元素以不同深度渗入材料内部,硬层为隐针马氏体及硼硅化合物。经检测,硬化层具有较高的硬度及合理的硬度梯度,具有优异的耐磨性及良好的耐蚀性。 相似文献
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钛合金表面阳极微弧等离子体渗硼层的研究 总被引:1,自引:0,他引:1
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。 相似文献
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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。 相似文献
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采用液相等离子体电解渗方法对Q235低碳钢进行硼碳共渗(PEB/C)处理,研究了Q235低碳钢表面硼碳共渗层的形貌、结构和显微硬度。评估了PEB/C处理前后Q235钢的电化学腐蚀性能,以及以GCr15钢球作为摩擦副在不同载荷条件下PEB/C渗层的摩擦磨损特性。结果表明,经过PEB/C处理后(330V/30min),形成厚度约为20μm并主要由Fe2B相组成的渗硼层。PEB/C处理轻微提高了Q235钢的耐腐蚀性能,但明显降低了Q235低碳钢与GCr15钢球对磨的摩擦因数和磨损率。当载荷为5N时,PEB/C样品的摩擦因数和磨损率分别是Q235钢基体的1/4和1/59。 相似文献
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激光重熔处理对渗硼层脆性的影响 总被引:5,自引:0,他引:5
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。 相似文献
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K. S. Keerthi Prasad M. S. Murali P. G. Mukunda 《Frontiers of Materials Science in China》2010,4(1):103-110
Centrifugal casting process is a fast process with melt, cast and moulds being opaque. It is almost impossible to observe
the melt behavior during casting. Cold modeling experiments were conducted using horizontal transparent moulds and transparent
fluids of different viscosities to study the effect of different process variables on the flow pattern. Effects of the thickness
of fluid cylinder, viscosity of the fluid, diameter of the mould, and rotational speed of the mould on the formation of complete
hollow fluid cylinder are investigated. The influence of rotational speed has been studied in aluminum casting. The cylinders
are cast at different rotational speed with varying thickness. It is observed that the speed required to form uniform cylinder
increases with the increase in thickness of a fluid cylinder. As rotational speed is increased the hardness of the cast cylinder
also increases. The flow patterns seen in cold modeling experiments and actual castings agree reasonably well. 相似文献
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用双层辉光离子渗金属技术,在TiAl合金表面渗入铬元素,形成合金层。研究了温度、气压、源极电压、阴极电压等工艺参数对渗层成分、厚度及显微组织的影响。结果表明,在源极电压700V、阴极电压450-280V、极间距18mm、试样温度1050℃、工作气压25Pa和保温时间4h的工艺参数条件下,渗铬层厚度可达60μm,渗层成分呈梯度分布,表面硬度明显提高。 相似文献
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Property modification by blending of polymers has been the area of immense interest. In this paper, the isomorphic blends of two polymers poly (vinyl fluoride) (PVF) and poly (vinylidene difluoride) (PVDF) with different ratios were prepared using solution cast technique. The microhardness studies have been carried out on pure and polyblend specimens at various loads to test the plasticization and hardening effects using Vickers microhardness testing. The X-ray diffraction (XRD) study has been utilized to detect the crystalline and amorphous characteristics of specimens. Thus PVDF acts as plasticizer in the polyblend when the content of PVDF is relatively high as compare to PVF. When the PVF is major component in the polyblend, the microhardness of the blend specimen increases and the isomorphic blend specimens with 50:50 proportion of two polymers exhibit the maximum value of microhardness. Scanning electron microscopy (SEM) micrographs indicate complete chain formation with uniform texture, when the two polymers are blended in equal proportions. The findings of XRD and SEM have been correlated with the microhardness values. 相似文献
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球形碳化钨增强金属基复合涂层具有高硬度、高韧性和优异的耐磨、耐蚀性等特点,可以对材料表面起到有效保护作用。传统铸造碳化钨粉体多呈不规则的片状或多角状,流动性差且硬度低,难以满足高性能涂层材料的要求。本文以多角状铸造碳化钨粉体为原料,采用感应等离子体技术制备球形碳化钨粉体,研究感应等离子体技术工艺参数对碳化钨粉体球化效果的影响规律。采用扫描电子显微镜、X射线衍射仪、霍尔流速计、激光粒度分析仪等对球化处理前后碳化钨粉体的形貌、物相、松装密度、粒度分布进行表征。结果表明:送粉率为110 g/min、载气流量为5.0 L/min时,采用感应等离子体技术可制备颗粒饱满、表面光滑、分散性良好,球化率高达99%以上,且球形度较好的球形碳化钨粉体。球化后碳化钨粉体无孔洞等缺陷,内部组织为典型的细针状WC和W2C的共晶,组织结构均匀细密。球化后碳化钨粉体的硬度高达3 258HV,提高了408HV;球化后碳化钨粉体的松装密度由8.01 g/cm3提高到9.75 g/cm3,霍尔流速由10.30 s/50 g降低到6.80 s/50 g,粉体的流动性提高。 相似文献
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Shuiqiang Zhang Zian Wang Yongsheng Han Yuqing Zheng Dongsheng Zhang 《Fatigue & Fracture of Engineering Materials & Structures》2020,43(1):110-118
Evaluation of the thermo‐mechanical behaviour and prediction of the service life of cast aluminium alloys are important for the design of automobile engine cylinder heads. In this study, cast Al alloy specimens are extracted from cylinder heads and subjected to in‐phase thermo‐mechanical cyclic loading. The hysteresis curves related to stress and strain were recorded under the individual thermo‐mechanical loading conditions. The number cycles to failure corresponding to multiple mechanical strain and temperature ranges were obtained. It is found that the cyclic stress amplitude decreases and the cyclic softening rate increases with increasing maximum temperature rise. A modified fatigue‐creep model based on energy conservation has been developed for prediction of the fatigue life of cylinder heads. The proposed method shows good agreement with the well‐established Ostergren model and low standard deviations. In summary, the proposed method described in this study provides an option for prediction of the thermo‐mechanical behaviour of metals. 相似文献
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Effects of conventional and active screen plasma nitriding on properties of electroless Ni–B coating
《Materials Science & Technology》2013,29(6):680-684
AbstractIn the present study, the properties of nitrided electroless Ni–B coatings prepared by conventional plasma nitriding and active screen plasma nitriding were investigated. For this purpose, electroless Ni–B coatings were deposited from an alkaline bath on AISI 4140 substrates. Then, some of the prepared coatings were plasma nitrided by conventional method and the other ones by active screen method under the same conditions. Microstructure, morphology, microhardness and wear resistance of the coatings were evaluated. Based on the results, post-treatments change the amorphous as deposited coating structure to a crystalline one, which increases microhardness and wear resistance. Employing plasma nitriding treatment on the coatings results in higher microhardness and superior wear resistance than conventional heat treatment. The sputtering of iron atoms during plasma nitriding process can be the main reason for these results. In addition, active screen plasma nitriding demonstrates less surface roughness and superior wear resistance than conventional plasma nitriding. 相似文献
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M. Yue F. Han‐guang M. Shang‐lin L. Yong‐ping 《Materialwissenschaft und Werkstofftechnik》2014,45(10):912-919
The effects of quenching temperature on microstructure and hardness of cast Fe–8Cr–2B alloy containing 0.3 wt% C, 2.0 wt% B, 8.0 wt% Cr, 0.6 wt% Si, and 0.8 wt% Mn were investigated by optical microscopy (OM), scanning electron microscopy (SEM), X‐ray diffraction (XRD), Rockwell hardness and Vickers microhardness testers. The experimental results indicate that the as‐cast microstructure of cast Fe–8Cr–2B alloy consists of M2B (M = Fe, Cr), M7(C, B)3, α‐Fe, and γ‐Fe. The dendritic matrix composed of lath martensite mixed with a small amount of retained austenite, and the netlike boride M2B distribute in the grain boundary. After quenching between 950 °C and 1100 °C, the netlike eutectic boride are broken up and a new phase‐M23(C, B)6 which is distributed in the shape of sphere or short rod‐like are precipitated from the matrix. Both the macrohardness and microhardness of specimens increase with the increasing quenching temperature. At about 1050 °C, the hardness reaches the maximum value. However, when the temperature exceeds 1050 °C, the hardness will decrease slightly. With the increase of tempering temperature, the hardness of cast Fe–8Cr–2B alloy quenching from 1050 °C decreases gradually and its impact toughness increases slightly. Crusher hammer made of cast Fe–8Cr–2B alloy quenching from 1050 °C and tempering from 300 °C has good application effect, and its service life improves by 150–180% than that of high manganese steel hammer. 相似文献