Nb-Ni-Ti-B强化药芯焊丝堆焊金属组织结构及耐磨性分析

针对Nb-Ni-Ti-B强化药芯焊丝堆焊金属进行研究,采用XRD和SEM分析了样品的相结构和显微结构;研究发现焊丝熔敷金属中的Fe2B能使熔敷金属堆焊层更加稳固,具有良好的抗剥离性能,Fe2B的硬度高、耐磨性好、分布均匀,镶嵌在熔敷金属的基体中有着骨架的作用,使该合金具有了良好的耐磨性;堆焊金属中的TiC为NbC提供了凝结核,形成NbC+TiC复合相,在提高耐磨性的同时有利于促进NbC弥散分布。NbC+TiC复合相弥散分布在熔敷金属中,部分NbC+TiC复合相嵌于Fe2B组织中有利于固化Fe2B组织。通过Nb-Ni-Ti-B强化药芯焊丝堆焊金属与5C-27Cr型高碳高铬合金焊丝熔敷金属磨损试验比较,Nb-Ni-Ti-B强化堆焊金属相对5C-27Cr型高碳高铬合金的耐磨性为2.08。     

Ti和Nb对铁基堆焊合金组织性能的影响

改变Ti或Nb的添加量制备Fe-Cr-C-B系铁基堆焊合金.借助扫描电镜、X射线衍射仪、洛氏硬度计和磨损试验机对堆焊合金组织性能进行测试分析.结果表明,在含Ti或Nb的堆焊合金中,初生奥氏体晶粒细化,共晶组织呈断网状均匀分布,并分别有黑色圆形或块状TiC和菱形或三角形NbC硬质相颗粒生成,添加5%Ti的堆焊合金组织最细小.TiC或NbC硬质相颗粒在组织中呈均匀弥散分布,能够作为耐磨质点与细化的初生奥氏体和共晶组织构成耐磨骨架,共同抵抗磨粒的楔入与切削作用.当Ti添加量为5%时,含Ti堆焊合金达到最优耐磨性,硬度为66 HRC,磨损量为0.048 7 g;当Nb添加量为4%时,含Nb堆焊合金达到最优耐磨性,硬度为65 HRC,磨损量为0.052 4 g.在同等条件下,含有适量Ti的铁基堆焊合金具有更优的耐磨性.     

原位生成NbC强化Fe-Cr-C堆焊层磨粒磨损性能

在Fe-Cr-C药芯焊丝中添加适量的铌铁粉,通过自动焊制备出含有适量原位生成的硬质相NbC的堆焊层。研究了硬质相NbC的出现对Fe-Cr-C堆焊层组织和性能的影响。结果表明Fe-Cr-C堆焊层中的M_7C_3略大。含有硬质相NbC的堆焊层初生碳化物大小和分布更加均匀,堆焊层硬度达到61.2 HRC,比Fe-Cr-C堆焊层的54.3 HRC提高了约12.71%,相对耐磨性提高49%。硬质相NbC的显微硬度达到2 234 HV。NbC的断面成不规则的多边形,NbC的分布不均匀,成团簇状聚集在一起。     

TiC对Ni35A堆焊层组织及摩擦磨损性能的影响

利用等离子弧对Ni35A及加入10%TiC的Ni35A预压块体进行堆焊试验,借助金相显微镜、X射线衍射仪、维氏硬度计及摩擦磨损试验机研究堆焊层组织及磨损性能。结果表明,堆焊层主要由(Fe,Ni)固溶体组成,加入TiC粉末后,堆焊层含硬质相Ni_3Ti及TiC,合金晶粒明显细化;焊层硬度增加,表层硬度提高了73%;磨痕深度、磨痕宽度、磨损量较Ni35A堆焊层的分别降低了38.9%、25.0%、57.6%。     

等离子弧堆焊TiC增强NiTi合金的组织和耐磨性

利用等离子弧堆焊方法在Q235钢板表面制备了添加TiC颗粒的NiTi合金耐磨堆焊层,并对堆焊层的微观组织和耐磨性进行研究.结果表明,在湿砂橡胶轮磨粒磨损试验条件下,当TiC加入量为55％时堆焊层的相对耐磨性最好,为Q235钢的11倍.TiC含量为55％的堆焊层由TiC、Ni3Ti及NiTi组成,堆焊层组织致密、与基材之间结合良好.堆焊层具有优异耐磨性的主要原因是TiC和Ni3Ti具有高硬度高耐磨性,起到抗磨骨架作用,而NiTi对TiC和Ni3Ti起到了支撑作用.堆焊层的磨损机制主要为塑性切削和硬质相的脆性剥落.     

铌含量对Fe-Cr-C熔敷金属组织与性能的影响

采用埋弧自动焊的方法制备出不同铌含量的Fe-Cr-Nb-C堆焊层,研究了铌含量对堆焊层微观组织结构和性能的影响,焊接过程中铌和碳发生反应生成NbC,随着铌含量的增加NbC数量增多,尺寸有所增大,堆焊层硬度和耐磨性能先增加后降低.当铌含量增加到一定程度时堆焊层中硬质相M7C3的数量减少,基体含碳量降低,组织软化.试验结果表明,铬含量在15 %左右、碳含量在4 %左右的情况下,铌含量为5 %左右最为合适,Fe-Cr-Nb-C堆焊层表现出优良的综合性能.     

Fe-Cr-C-B-Nb堆焊合金的显微组织和耐磨性

采用明弧自保护法制备Fe-Cr-C-B-Nb系耐磨堆焊合金,借助光学显微镜(OM)、扫描电镜(SEM)和X射线衍射(XRD)等手段,分析堆焊层中的物相组成,探究熔池中硬质相析出顺序,研究B和Nb元素含量对其显微组织和耐磨性影响. 结果表明,制备的堆焊合金显微组织为马氏体+残余奥氏体+ M23(C,B)6+NbC,NbC先于M23(C,B)6生成. 当堆焊层中B元素含量为0.21%,Nb元素含量为1.44%时,可以使堆焊合金有较高的硬度和耐磨性. 洛氏硬度可达69 HRC±1.5 HRC,磨损量为0.037 6 g. 过量的B元素不利于NbC析出,而使Nb元素固溶强化硼化物和基体. 耐磨性试验结果表明,M23(C,B)6和NbC两种硬质相显著改善了Fe-Cr-C-B-Nb系堆焊合金的耐磨性.     

原位合成TiC-M7C3金属复合涂层

为提高钢基材的耐磨性能,采用等离子堆焊技术,制备了原位自生M7C3-TiC增强铁基堆焊层。利用金相显微镜、扫描电镜、X射线衍射仪及显微硬度计对堆焊层的组织和性能进行了测试。结果表明:堆焊层与基体之间形成了良好的冶金结合;堆焊层表层组织由马氏体、(Fe,Cr)7C3和TiC构成;初生(Fe,Cr)7C3呈六边形,晶粒尺寸较大,均匀弥散分布在堆焊层中,TiC颗粒呈开花状、立方体或团聚状;堆焊层硬度从基体到表面呈合理的梯度分布,较基体有显著提高。     

几种表面耐磨工艺的磨料磨损实验研究

采用表面堆焊工艺制备Fe-Cr-C、Fe-Cr-C-NbC两组堆焊试样,采用感应钎焊工艺制备YG8硬质合金钎焊试样,对试样的组织和耐磨性能进行了研究。结果表明,亚共晶Fe-Cr-C堆焊合金的显微组织主要为马氏体+共晶碳化物,其耐磨性较40Cr淬火钢有一定提升。添加3%~5%的NbC后,堆焊合金层中形成大量弥散分布的块状NbC硬质相,阻碍了磨粒对基体的切削作用,其耐磨性是Fe-Cr-C堆焊合金层的3.3倍。YG8硬质合金硬度为1280HV,相对耐磨性为Fe-Cr-C堆焊合金的29.8倍,表现出极高的耐磨性。     

NbC增强Fe-Cr-C耐磨堆焊合金组织与磨粒磨损性能

以H08A为焊芯,在Fe-Cr-C耐磨合金焊条药皮中加入NbC,对堆焊层组织及NbC对堆焊层硬度和耐磨性的影响进行了研究.结果表明,NbC增强Fe-Cr-C耐磨合金的宏观硬度和耐磨性都高于Fe-Cr-C合金,宏观硬度达到61.6 HRC,比Fe-Cr-C耐磨合金提高9.6%;相对耐磨性提高60%.NbC增强Fe-Cr-C耐磨合金中NbC硬质相断面呈不规则形状,分布于M7C3之间,或镶嵌在M7C3中,以菱形或多边形居多,NbC分布不均匀,有局部聚集的区域.与Fe-Cr-C耐磨合金的共晶碳化物比较,Fe-Cr-C-NbC合金的共晶碳化物要粗大,共晶碳化物的间距也较大.     

MICROSTRUCTURES AND OXIDATION RESISTANCE OF Fe3Al WELD OVERLAY

1. Introduction Iron aluminides based on Fe3Al are candidates for a variety of structural applications because of their excellent oxidation and sulfidation resistance, low density and high strength at elevated temperatures. However, low ductility and poor machinability have restricted their uses as engineering materials[1,2]. Weld overlaying is a surfacing process, which has been widely used to repair or fabricate products in industry[~J. By depositing Fe3AI on stronger base materials, the…     

无熔滴电弧热丝GTAW自润滑耐磨堆焊层组织及性能

目的采用无熔滴电弧热丝GTAW堆焊技术,在Q235钢表面堆焊具有自润滑功能的含石墨相耐磨合金。方法设计含有镍包石墨粉的药芯焊丝,并使用无熔滴电弧热丝GTAW堆焊技术和传统GMAW两种方法进行对比堆焊。焊后,采用销盘式摩擦磨损试验机对堆焊层进行对比摩擦磨损性能测试,利用光学显微镜、SEM和EDS研究堆焊层的微观结构及成分,并对磨损面形貌进行对比分析,探究自研焊接系统制备含石墨相堆焊层的工艺特点和堆焊层自润滑耐磨性能。结果无熔滴电弧热丝GTAW可以有效降低母材的稀释率,保证药芯焊丝自润滑石墨相过渡,且能提高熔敷率。堆焊层形成了Fe-Cr-B耐磨基体,并在晶界处分布大量的颗粒状石墨相。摩擦磨损实验中,堆焊层摩擦系数可低至约0.65,随着摩擦时间的延长,摩擦系数进一步减小,磨损面未发现典型犁沟,表面平滑且呈黑色,堆焊层具有自润滑功能,且摩擦系数与焊接参数有关。传统GMAW方法制备的堆焊层的摩擦系数为1.4左右,且随着磨损时间的延长,摩擦系数略有增大。结论无熔滴电弧热丝GTAW堆焊技术低热输入和高熔敷率的工艺特点适合堆焊,尤其适合防止焊丝化学成分烧损的堆焊。在合理控制工艺参数,焊接稳定的前提下,选择低辅助电流,可以成功制备含石墨相的自润滑耐磨堆焊层。     

核级ENiCrFe-7镍基合金电焊条的研制

迄今,核电设施的焊接用镍基合金电焊条都依赖进口。为此,成功研制了核级ENiCrFe-7镍基合金电焊条,并在低合金钢板上制备了约20mm厚的堆焊层。随后检测了焊缝金属的宏观和微观形貌及室温和350℃力学性能,并对其进行了弯曲试验、剪切试验、晶间腐蚀试验和STF(strain-to-fracture)试验。结果表明:焊缝金属的宏观质量、微观组织、力学性能和耐晶间腐蚀性能均符合第三代先进压水堆核电站的要求,并且对高温失塑裂纹(DDC)不敏感。新研制的核级ENiCrFe-7镍基合金电焊条的综合性能与进口焊条的相当,有望替代进口的焊条。     

硅钨酸修饰多晶铂电极及其电催化性能

通过循环伏安扫描制备了硅钨酸修饰多晶铂电极，在电极制备过程中发现，SiW12在Pt电极表面的氢区发生了氧化-还原反应，而在氧区使电极表面含氧粒子的吸附增加。通过循环伏安和恒电位I-t曲线研究了该修饰电极在硫酸溶液中的电化学行为和对甲醇氧化的电催化作用。研究结果表明：硅钨酸修饰多晶铂电极提高了甲醇氧化的催化活性和抗CO中毒性。     

Behaviour of coatings with AWS ERNiCrMo-3 electrode on ASTM A516 Gr.60 steel in ageing tests

This work is intended to evaluate the microstructure of nickel-based overlay welds after ageing heat treatments. GMA welds using an AWS ERNiCrMo-3 electrode were deposited with a robot on ASTM A516 Gr.60 steel. Two weld heat inputs were used, 1.0 and 1.4 kJ/mm, with a current of 290 A, arc voltage of 33 V, and welding speeds of 9.7 and 6.8 mm/s, respectively. The ageing processes were conducted at 600°C using times of 100 and 300 h. Micro-hardness profiles and scanning electron microscopy together with energy dispersive spectrometry analysis were carried out to characterize the overlay. The hardness profile indicated that, in the ‘as welded’ condition, the overlay and heat-affected zone (HAZ) hardness were about 240 and 190 VH, respectively. The ageing process decreased the HAZ hardness to 120 VH and increased the overlay hardness to 290 VH after 100 h and to 310 VH after 300 h. These changes occurred due to HAZ decarburization and transformation of micro phases. After ageing, hard zones with values of around 800 VH were observed in the partially diluted zone, caused by the higher concentration of carbides and microstructural changes.     

A comparative experimental study of machining characteristics in vibratory, rotary and vibro-rotary electro-discharge machining

This paper compares the effects of high- and low-frequency forced axial vibration of the electrode, rotation of the electrode, and combinations of these methods in respect of material removal rate (MRR), tool wear rate and surface roughness in die sinking electro-discharge machining (EDM) with a flat electrode (planing mode).

The results of the combined states of rotation and vibration at high and low frequency (vibro-rotary EDM) are compared in order to establish which combinations are most appropriate to different machining regimes (finishing, semi-finishing and roughing). It is found that the combination of high-frequency vibration and rotation of the electrode is effective in attaining a high MRR at a specified surface roughness (R_a). This case is modelled by stepwise linear regression. The significant parameters are found by analysis of variance (ANOVA) and the optimum machining parameter settings are obtained using overlay contour plots. The advantages of vibration and rotation are seen to combine in this new process when employed for die sinking EDM with a flat electrode.     

改性J422焊条电弧焊碳钢接头在亚硫酸铵溶液中的耐蚀性

针对亚硫酸铵介质中碳钢焊接接头腐蚀严重的实际,采用向普通碳钢焊条J422药皮中添加镍的方法,以三电极电化学研究方法和金相组织分析法研究了焊缝不同含镍量情况下碳钢焊接接头在亚硫酸铵溶液中的腐蚀行为.结果表明,镍元素的加入使得焊缝组织晶粒细化,针状铁素体减少;同时提高了碳钢焊接接头的自腐蚀电位;焊接接头在亚硫酸铵溶液中的极化率增大,自腐蚀电流减小;其中焊缝Ni元素含量为1.2%的焊接接头腐蚀速率最小.     

电极材料对含S碱液电化学氧化脱硫的影响及应用

采用全玻璃电解池装置,辅助电极为Pt网,以含S碱液作为电解液.研究不同的电极材料对S化物电化学氧化脱S的影响.它们分别为Pt电极、石墨电极和Ru-Ti电极.结果表明,电极材料对S离子电化学氧化过程有显著影响.据此,选择了工业模拟实验的工作电极——Ru-Ti电极,研制了一套多级电化学脱除H2S工业模拟装置     

A new method to improve surface morphology of Ni-Fe-Mo-Co alloy electrode and its catalytic activity for HER

A new pretreatment method has been developed to improve the catalytic activity of the Ni-Fe-Mo-Co alloy elec- trode for hydrogen evolution reaction (HER). The procedure involves pre-electrolyzing the Ni-Fe-Mo-Co alloy electrode in 30% KOH solution containing 10% potassium sodium tartrate at 70°C for 2 h, until some of the Mo and Fe elements are leached out. The surface morphology of the Ni-Fe-Mo-Co alloy demonstrates a unique hive-like structure after the pre- treatment, which has the pore size in a nanometer range (about 50 nm), a very large real surface area, and good stability. The results of the electrochemical studies show that compared to other similar electrode materials and the treated Ni-Fe-Mo-Co electrode by leaching method, the pre-treated Ni-Fe-Mo-Co electrode has a much lower overpotential and much higher exchange current density for HER. In addition, a long-term continuous electrolysis test with a current interrup- tion shows that the Ni-Fe-Mo-Co alloy has excellent catalytic stability.