Electrochemical investigation on hydride electrode with tungsten carbide additive

1　ＩＮＴＲＯＤＵＣＴＩＯＮＧｅｎｅｒａｌｌｙ,ｉｎｔｈｅｃｈａｒｇｅ (ｃａｔｈｏｄｉｃ) ｐｒｏｃｅｓｓｏｆｈｙｄｒｏｇｅｎｓｔｏｒａｇｅａｌｌｏｙｅｌｅｃｔｒｏｄｅｓ,ｔｈｅｅｌｅｃｔｒｏｌｙｓｉｓｏｆｗａｔｅｒｔａｋｅｓｐｌａｃｅａｎｄｔｈｅａｔｏｍｉｃｈｙｄｒｏｇｅｎｆｉｒｓｔａｄ ｓｏｒｂｓｏｎｔｈｅｓｕｒｆａｃｅｏｆｅｌｅｃｔｒｏｄｅａｃｃｏｒｄｉｎｇｔｏｒｅａｃｔｉｏｎ(1 )ａｔｔｈｅｐｏｔｅｎｔｉａｌｏｆ -0 .82 8ＶｖｓＨｇ/ＨｇＯ .Ａｓｔｈｅｃａｔｈｏｄｉｃｐｏｔｅｎｔｉａｌ (ａｂｓｏｌ…     

A study on the fine-finish die-sinking micro-EDM of tungsten carbide using different electrode materials

In recent years, tungsten carbide (WC) and its composites (WC–Co) are widely used in the die and mold industries due to their unique combination of hardness, strength and wear resistance. Micro-EDM is one of the most effective methods for machining these extremely difficult-to-cut materials. However, numerous applications of WC often involve intense mechanical demands at the surface. Therefore, fine-finish micro-EDM of WC is becoming an imminent and important issue. In this study, investigations have been conducted with view of obtaining fine surface finish in the micro-EDM of WC using tungsten (W), copper tungsten (CuW) and silver tungsten (AgW) electrodes. It was found that the surface characteristics are dependent mostly on the discharge energy during machining. The fine-finish micro-EDM requires minimization of the pulse energy supplied into the gap. In addition, the surface finish was found to be influenced greatly by the electrical and thermal properties of the electrode material. The performance of the electrodes for the finishing micro-EDM was evaluated based on the achieved surface roughness and surface characteristics with respect to material removal rate (MRR) and electrode wear ratio (EWR). It was found that AgW electrode produces smoother and defect-free nanosurface with the lowest R_a and R_max among the three electrodes. Besides, a minimum amount of material migrates from the AgW electrode to the WC workpiece during the finishing micro-EDM. On the other hand, CuW electrodes achieved the highest MRR followed by AgW. In the case of electrode wear, the W electrode has the lowest wear followed by CuW and AgW. Finally, considering all the performance parameters, AgW appears to be the best choice for finish die-sinking micro-EDM of WC.     

Ti17合金表面电火花沉积硅青铜涂层

用硅青铜(QSi3-1)电极,分别在硅油和氩气中对Ti17钛合金进行了电火花表面强化.利用扫描电镜、X射线衍射仪、辉光放电光谱仪、显微硬度计和MM200磨损试验机等对强化层的成分、组织、硬度和耐磨性进行了研究.结果表明,用QSi3-1电极在氩气和硅油中于30V、1500μF的电参数下.分别可获得显微硬度高达HV550和HV494、厚度约10μm和5μm的强化层;前者所得强化层以Ci3Cu、Cu为主,同时还有少量的TiSi2和Ti;后者所得强化层由Ti3Cu和Cu相及少量TiO、Ti2N、Ti3SiC2相组成;在试样转速为200r/min,干圆环摩擦磨损条件下、在氩气和硅油中强化试样的磨损量仅为钛合金基体的1/56和1/24.钛合金基体主要以氧化磨损和粘着磨损为主;表面改性层磨损的原因则与强化层脱落造成磨粒磨损有关.     

金刚石钻头胎体材料碳化钨一铸钢丸的试验研究

本文介绍了一种新的金刚石钻头胎体材料碳化钨-铸钢丸,这种钻头体材料的特点是钻头体表面使用铸造碳化钨材料,心部使用铸钢丸材料,从而实现钻头体表面耐磨抗冲蚀,心部高强高韧的特点.测试了这种钻头体心部材料的力学性能和表层材料的耐磨抗冲蚀能力,同时还介绍了使用含胶碳化钨粉涂抹在钻头模具表面和石墨替棒表面的方法.由于钻头体心部力...     

Investigation of coatings produced by the electrospark machining method of steel 45 with electrodes based on carbides of tungsten and titanium

The article is devoted to the development and investigation of tungsten-containing and tungstenless electrode materials for electrospark alloying using additives of boron-containing minerals, as well as aluminum-oxide nanopowder. The kinetics of the mass transfer process with the electrospark alloying of coatings was investigated. The phase composition, roughness, and kinetics of high-temperature oxidation of coatings were studied. The anticorrosive properties of obtained coatings were studied in 3% NaCl solution by the method of impedance spectroscopy. An improvement of the barrier properties of TiC–Ni–Mo coatings with increasing datolite concentrate was revealed.     

H13钢表面电火花沉积WC涂层

利用DZ-4000(Ⅲ)型电火花沉积/堆焊机,以WC为电极材料,采用氩气为保护气对H13钢基体进行了电火花表面强化.利用扫描电镜、能谱分析仪、X射线衍射仪和显微硬度计等对沉积层的成分、组织、硬度和表面粗糙度进行了研究.结果表明,利用电火花沉积工艺可获得组织均匀、致密,且与基体呈冶金结合的沉积层,沉积层平均厚度约60μm.沉积层主要由Fe3W3C、(CrFe)7C3和W2C等相组成.沉积层的平均显微硬度为1321.4 HV0.05,约为基体硬度的3倍.     

高能离子注渗碳化钨切分轮

为提高切分轧制中切分轮的综合性能，采用了高能离子注渗技术，在合金结构钢表层内形成0．3～0．5mm的碳化钨富集层，其平均使用寿命比高速钢切分轮提高3．23倍，经济效益显著。     

Sintering of tungsten carbide particles sputter-deposited with stainless steel

The purpose of this work was to study the sintering process of WC–stainless steel AISI 304 composite powders prepared by an innovative process, which consists in the use of a magnetron sputtering to coat WC powder particles with the stainless steel elements. The sintering of pressed compacts was performed in a conventional vacuum furnace using a heating rate of 5 °C min⁻¹ until the selected maximum temperature, a holding time of 50–173 min and a sintering pressure of 2–20 Pa. For comparison, a conventional prepared WC powder with 6.5 wt.% of stainless steel AISI 304 was also studied.During the sintering of the coated powders, three different sintering stages were identified: an initial one due to solid state matter transport until ∼1150 °C, followed by two other stages where liquid phase may be already present. Very high weight losses occurred during the sintering of coated powder which was diminished by the shortening of the holding time, the increase of the pressure in the sintering furnace and the appropriate control of the sintering atmosphere. Despite the high values of weight loss, 96% of densification can be obtained at a relatively low sintering temperature, T=1325 °C, for an initial content of ∼10 wt.% of binder phase.     

铜电极表面电火花沉积ZrB_2-TiB_2复相涂层

采用粉末冶金法制备Zr B2-Ti B2复相材料熔敷棒,并通过电火花沉积工艺在铜电极表面制备Zr B2-Ti B2复相涂层。通过扫描电镜结合能谱分析研究了涂层的显微结构和元素分布,利用X射线衍射和显微硬度测试对涂层的物相组成与显微硬度进行检测。结果表明:直接熔敷Zr B2-Ti B2复相涂层致密性较差,且存在较多裂纹,与基体有明显分层,涂层物相为Cu、Zr B2和Ti B2;在预沉积Ni层(Ni层)上后沉积Zr B2-Ti B2,所得的多层涂层具有较好的致密性,且涂层与基体间无分层;中间层有Ti、Zr、Cu元素的扩散,说明涂层与基体为冶金结合;Zr B2-Ti B2复相涂层硬度为900 HV0.05稍高于多层涂层硬度(800 HV0.05)。     

Formation of composite coatings based on titanium carbide via electrospark alloying

This work concerns studying the coatings prepared via electrospark alloying. To deposit the coatings, we used STIM-2/30 electrodes derived from a combination of self-propagating high-temperature synthesis (SHS) and extrusion. It was found that the composite coating is formed from titanium carbides and a solid solution of nickel in iron and contains both large (4–5 μm) and small carbides (less than 1 μm); in addition, large grains of titanium carbide are formed in the central portion of the coating, and the grain size decreases to 100 nm while approaching the transition zone. Large grains of titanium carbide in the coating consist of dispersed carbides with sizes less than 1 μm. It is determined that the composition of the substrate has an effect on the size of the transition and diffusion zones. It ranges from 17 μm for steel 9KhSA to 26 μm for steel 20; that is, the higher the degree of alloying, the less the depth of the modified layer.     

点焊电极表面电火花沉积TiB_2涂层的特征

在CuCrZr电极表面通过电火花振动沉积制备了TiB_2功能涂层,测试了功能涂层的显微形貌、物相、硬度以及界面元素分布.试验表明,TiB_2涂层电极具有典型的电火花涂层结构,存在明显的元素互扩散,表明功能层与基体之间为冶金结合.但TiB_2涂层结构不致密,存在裂纹和孔洞,硬度较低.随着电火花电容和电压的增加.涂层的硬度降低.元素扩散和涂层氧化的加剧,是导致涂层硬度降低的主要原因.由于基体Cu的气化、脆性剥落和熔敷棒的切削作用,沉积TiB_2后基体质量反而降低.高电压下电火花沉积以及预涂敷Ni,都会导致基体质量降低更多.     

电火花沉积法在铜电极表面制备TiB2/Ni涂层

为了提高镀锌钢板用点焊电极的使用寿命,在铜电极表面涂覆过渡层Ni后沉积了TiB2涂层。通过SEM和XRD分析了Ni和TiB2涂层的物相和微观结构,并测试了其显微硬度。结果表明：由于材料具有良好的塑性,预涂覆的Ni涂层结构致密无裂纹,与基体Cu无分层;而TiB2涂层内存在裂纹和孔洞。通过过渡层Ni将TiB2涂层和基体Cu粘结起来,获得了较理想的涂层。随着电火花放电电容和电压的增加,TiB2的氧化程度增强,Cu和Ni大量扩散进入涂层表面,使TiB2/Ni涂层的硬度降低。由于TiB2良好的导电和导热性能及高的硬度,TiB2/Ni涂层电极在点焊时的塑性变形降低,寿命比无涂层电极和TiC涂层电极得到了明显提高。     

Effect of tungsten on carbide formation in steel 30KhG

Conclusions Alloying of Cr-Mn steel with tungsten inhibits diffusion processes, due to which the temperature at which elements are redistributed between the matrix and iron carbide increases. Alloyed chromium carbide is formed in the steel with 0.75% W in the process of tempering at 600°C. In the steel with 1% W chromium carbide is formed at 575°C. Hexagonal chromium carbide is formed in these steels due to gradual rebuilding of orthogonal iron carbide. Raising the tungsten content to 1.25% causes substantial enrichment of cementite with tungsten, and at 600°C hexagonal carbide (W, Cr)₂C is formed by the aging mechanism, the tungsten content increasing considerably, and the concentrations of chromium, iron, and manganese decreasing, with increasing temperatures. A larger tungsten content leads to formation of carbide identified as tungsten carbide W₂C.Institute of Problems of Casting, Academy of Sciences of the Ukrainian SSR. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, pp. 9–13, June, 1979.     

Effect of electrospark surface alloying on the wear resistance of steel

Metal Science and Heat Treatment -     

Structure and properties of a hard alloy based on tungsten carbide with Fe-Ni binder

Conclusion The x-ray structural and metallographic analysis showed that alloys with Fe-Ni binder undergo complete transformation after heat treatment, as was confirmed by measurements of the microhardness of the binder, which increased H 200 after heat treatment. The bending strength and hardness of the alloys also increased considerably after heat treatment.All-Union Scientific-Research and Design Institute of Refractory Metals and Hard Alloys. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 56–57, May. 1978.     

激光熔覆原位合成碳化钨增强铁基表面复合材料的研究

利用激光熔覆原位合成技术,在预置N i涂层的45钢表面原位自生碳化钨陶瓷。通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)、显微硬度计等分析测试手段对碳化钨陶瓷增强相的组织形貌、物相组成、化学成分及力学性能等方面进行了研究。结果表明,熔覆区内的碳化物由过饱和固溶体共晶析出;涂层与基体间的结合为冶金结合;制备的表面复合材料的硬度高于基体,改性效果极为明显。     

铸钢材料电火花表面沉积WC-4Co涂层的组织与性能

采用电火花沉积工艺,在铸钢表面制备了WC-4Co沉积涂层,采用X射线衍射仪、扫描电镜、显微硬度计等对沉积层的相结构、显微组织、显微硬度及耐磨性能进行了分析.结果表明:沉积层主要由Co3W3C、Fe3W3C、W2C、Fe7W6等相组成;沉积层与基体呈冶金结合,Fe7W6、W2C等硬质相弥散分布于沉积层中,部分区域硬质相达到了纳米颗粒尺寸;沉积层的平均硬度为1517HV0.3,约是基体硬度(502 HV0.3)的3倍;其耐磨性能比基体提高了2.4倍;沉积层的主要磨损机制为疲劳磨损,细小的弥散分布的硬质相是沉积层硬度以及耐磨性能提高的主要因素.     

塑料模具钢表面激光熔覆WxC/Ni基合金涂层的组织及性能

采用TJ-HL-5000横流CO2连续激光器在2738塑料模具钢表面制备了WxC/Ni基合金涂层.利用金相显微镜、SEM、EDS、XRD、显微硬度计以及摩擦磨损试验机等检测设备研究了激光熔覆涂层组织及性能.XRD分析结果表明,熔覆层的主要物相有γ-Ni、W2C、WC、M23C6(M=Cr,Ni,Mo,W)、NiCr和Cr2O3等.金相显微镜、SEM和EDS分析结果表明,结合区为良好冶金结合,结合区为FeNiCrW合金,厚度为20 μm左右;基体对熔覆层合金的稀释度很低;熔覆层从界面向外依次分布着平面晶区、细等轴晶区、粗树枝晶区以及表面细晶区.显微硬度计结果表明,熔覆层的硬度值平均约900 HV1,是基体硬度的2.8倍左右.摩擦磨损试验结果表明,与基体相比熔覆层的耐磨性有了很大提高.     

化学脱钴对硬质合金沉积金刚石薄膜的影响

采用HFCVD系统,以CH4和H2为反应气体,分别在YG3、YG6、YG10、YG13硬质合金上沉积了金刚石薄膜,研究了化学脱钴处理对不同钴含量硬质合金沉积金刚石薄膜的影响.通过对105个样品的实验结果进行统计分析发现,YG3所得金刚石薄膜样品具有足够结合强度的比例为89%;而YG6、YG10 和YG13所得样品的相应值分别为24%、7%和0%.相反,YG3、YG6、YG10 和YG13所得金刚石薄膜严重破坏的比例分别为0%、64%、72%和79%.研究表明,化学腐蚀脱钴处理能够解决金刚石涂层形核率低的问题,但难以解决高钴硬质合金的附着性差的问题.