Effect of RE on Granulation of Eutectic Carbide in Ledeburite Steel

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燃烧合成三元碳化合物Ti2AlC1-x

采用Ti，Al和C元素粉末为反应物原料，通过燃烧合成法首次成功地制备出了单相三元碳化合物Ti2AlC1-x。实验结果表明：若以“理想”晶体结构化学式Ti2AlC化学计量比为起始反应原料配比，燃烧产物主晶相为Ti2AlC2；以缺碳的非化学计量比(Ti2AlC1-x)为反应原料配比，即Ti：Al：C=3：1．5：1=2：1：0．7(摩尔比)，得到单相的燃烧产物Ti2AlC1-x。从热力学原理的角度探讨了不同原料摩尔配比对燃烧产物相组成的影响机理。     

长期高温服役的12%Cr耐热合金钢性能退化与恢复

X2 0CrMoV12 1耐热合金钢广泛应用于热电厂主蒸汽管线等主要部件。经长期高温负荷运行后 ,材料性能明显退化。观察显微组织发现 ,材料性能下降是和晶界碳化物的粗化密切相关的。文章着重研究了损伤材料重新热处理后的性能和组织结构的变化 ,初步探讨了材料长期服役后通过热处理恢复其原始性能的可能性     

关于硬质合金行业技改项目合同管理的思考

就硬质合金行业技改项目在实施过程开展有关合同管理的问题进行分析讨论,并提出应对措施,对搞好硬质合金行业技改项目合同管理工作具有现实意义。     

Effect of SiC nanowhisker addition on microstructure and mechanical properties of regenerated cemented carbides by low-pressure sintering

The hardness and toughness of regenerated cemented carbides, in general, are contradictory. Therefore, it is critical to explore regenerated cemented carbides with both high hardness and high toughness. In this study, regenerated WC-8-wt% Co cemented carbide with SiC nanowhisker were prepared by low-pressure sintering. The influence of SiCw contents on the microstructure and mechanical properties of regenerated WC-8-wt% Co cemented carbide was investigated. The results indicated that the hardness, density, flexural strength, and fracture toughness of regenerated cemented carbide first increased and then decreased with the addition of SiCw. The Vickers hardness, density, flexural strength, and fracture toughness could reach 1575 HV, 14.6 g/cm³, 2204 MPa, 16.85 MPa·m^1/2, respectively, with SiCw content 0.5 wt%, which were increased by 14.4%, 0.7%, 12.2%, and 17.3%, respectively, when compared with the regenerated cemented carbide without SiCw. The lowest friction coefficient and the best wear resistance could be also reached when 0.5-wt% SiCw was added. The fracture mechanism of the regenerated cemented carbide contained both transgranular and intergranular fracture through the microscopic observation of fracture surface via scanning electron microscope.     

Microstructure and properties of WC-8Co cemented carbides prepared by multiple spark plasma sintering

In this study, WC-8Co cemented carbides were prepared by spark plasma sintering. When the samples sintered at 1300℃ were cooled to room temperature, the samples were sintered multiple times at 1250℃. The changes in microstructure and mechanical properties of WC-8Co cemented carbides prepared by multiple spark plasma sintering were studied. The hardness of cemented carbides increased in the first two sintering, reaching 16.5 GPa. However, the hardness decreased seriously in the last two sintering. The attenuation rates of hardness were 6.2% and 2.5% due to the abnormal coarse grains. Furthermore, the crack path along the grain boundary was almost straight, causing a decrease in the indentation fracture toughness of cemented carbides. Additionally, the grains of cemented carbides were abnormally coarsened, and the morphologies of grains became unstable due to multiple sintering.     

Ni/W比对NiWCx催化剂加氢性能的影响

过渡金属碳化物具有类似贵金属的电子结构和加氢性能。采用等体积浸渍法制备了不同Ni/W比的NiW/γ-Al₂O₃催化剂,以程序升温碳化法转化为NiW碳化物后对芳烃模型化合物和低温煤焦油中分离所得芳烃组分进行加氢处理。催化剂的N₂吸附、XRD、H₂-TPR和SEM表征表明,Ni的添加促进了载体表面WO₃物种的分散和还原,抑制了WO₃晶体的团聚和大晶粒的生成。萘的加氢实验表明,Ni/W原子比为0.6时催化剂的活性最佳,而添加苯酚和吡啶后的模型油加氢过程中萘的转化率和十氢萘的产率均明显下降,Ni/W原子比为0.47和0.6的催化剂性能相近,煤焦油中芳烃组分加氢后Ni/W原子比为0.47的催化剂性能更优。结果表明,Ni和W均具有良好的加氢活性,但Ni耐杂原子性能较差,二者存在一个最佳的配比以使加氢性能更优。有杂原子化合物存在时,如煤基芳烃组分的加氢,Ni/W原子比为0.47的NiW碳化物催化剂具有更好的加氢性能。     

Formation of a chromium-carbide conversion coating on silicon carbide

The formation of a chromium-carbide conversion coating on SiC was achieved using the pack-cementation technique. The conversion coating is intended to improve the corrosion resistance of SiC and its derivatives, such as SiC-base continuous fibers and composites, by forming a protective Cr₂O₃ scale upon exposure to high-temperature corrosive environments. Different pack chemistry and processing parameters were evaluated in the laboratory. Results indicated that the coating morphologies and compositions achieved were significantly affected by variation of these processing factors. In this paper, the conversion coating obtained from one of the systems investigated is reported. The coating consists of a multilayered structure with each of the sublayers containing a high-Cr concentration. In addition, the coating surface is relatively dense and pore free compared to the underlying SiC substrate material. A dense and pore-free morphology is highly desirable for coating applications, especially on porous substrates. The multilayered coating structure consists of the following sublayers: Cr₂₃C₆/Cr₇C₃/Cr₇C₃+Cr₃Si/Cr₅Si₃C_x/SiC substrate.     

低成本钢尾渣-矿渣基矿山充填料的优化开发

 为实现多固废协同利用、降低充填成本,在矿渣基全粒级细尾砂胶结充填料基础上,以流动性和抗压强度为表征,利用热闷钢渣磁选尾渣(钢尾渣)替代部分矿渣作为胶凝材料,脱硫灰和水泥熟料替代部分专用添加剂作为外加剂,采用正交试验探寻掺量规律,优化固体填充料配比,开发钢尾渣-矿渣基软性矿山充填料,并研究了外加剂与胶材比、灰砂比等因素的影响。对比分析了矿渣基准组、钢尾渣-矿渣基准组(B1)、强度最优外加剂组分钢尾渣-矿渣组(B7)等3组充填料的微观形貌及XRD图谱以探究其水化机理。结果表明,钢尾渣替代矿渣量增加、外加剂与胶材比减小,充填料浆流动性改善,但充填体抗压强度下降。强度正交试验结果表明,钢尾渣掺量大小决定强度低高,脱硫灰掺量宜高于水泥熟料。进一步调整外加剂组分配比,在灰砂比为1∶6、钢尾渣替代矿渣为20%条件下,找出B7组外加剂组分为脱硫灰、水泥熟料分别替代30%、20%专用添加剂,B7组料浆扩展度为143 mm,充填体形貌为富铁绿泥石胶结假方体钙硅灰石,28 d抗压强度达2.13 MPa,较基准组低0.19 MPa,较B1提高0.26 MPa。该替代方案满足现场充填C2级强度的要求,改善流动性并显著降低了充填成本。优化的外加剂组分配比在灰砂比为1∶4条件下同样具有强度优化作用,但较灰砂比为1∶6条件下低。     

熔渣法碳化铬涂层的抗氧化性能研究

对熔渣法碳化铬涂层在各种温度下经20h和200h的氧化性能进行了研究，与常用的一些锅炉用钢进行了对比试验，结果表明碳化铬涂层抗氧化性能比15CrMo、102、T91钢好，可以与TP347钢相媲美。