共查询到20条相似文献,搜索用时 31 毫秒
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人们衡量堆焊方法一般总是从两个方面进行 ,一是熔敷速度 ,二是稀释率。在追求大熔敷速度的同时总是希望将稀释率控制得尽量小。目前 ,国内堆焊方法大都处于高熔敷速度高稀释率或低稀释率低熔敷速度的状态。熔敷速度的提高和稀释率的降低是矛盾的两个方面 ,二者相互制约。能否协调熔敷速度与稀释率之间的矛盾关系 ,是能否实现高效、高质的堆焊工艺的关键。等离子弧作为粉末堆焊的热源 ,其焰流特性参数是影响堆焊质量和效率的主要因素。本文从理论上定性分析了等离子弧的焰流特性参数和粉末在电弧中获得的动量和热能情况 ,阐述了实现高效、低稀释率等离子堆焊的机理 ,并据此提出了新型焊枪结构的设计原则 ,为进一步研制高效、低稀释率等离子堆焊系统奠定了理论及试验基础。 相似文献
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利用碳极氩气拘束电弧进行了粉末堆焊试验,发现其母材稀释率远比其它电弧堆焊方法低得多,而且合金元素过渡系数高。作者认为其稀释率低与电弧温度分布及压力分布均匀、温度适中、电弧气氛具有一定还原性的特点有关。电弧径向温度分布及压力分布均匀可使熔池的熔深均匀,不易形成锅底形熔池,故稀释率低;温度适中既提高了熔敷效率又有利于降低合金烧损;还原性的电弧气氛及氩气的保护作用有利于降低合金元素烧损,从而提高合金元素的过渡系数,并且提高熔敷层对母材的润湿性。其综合作用使碳极氩气拘束电弧堆焊稀释率低,合金元素过渡系数高。 相似文献
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Victor Vergara Diaz Jair Carlos Dutra Ana Sofia Climaco Monteiro D'Oliveira 《Welding International》2013,27(2):87-95
The plasma powder transferred arc welding process which uses feed stock in a powder form has similarities with plasma wire transferred arc welding. This paper describes a comparative study of the two processes using a cobalt-based alloy commercially known as stellite 6. This Co-based alloy is recognized for its superior cavitation erosion resistance. The aim of this paper is to investigate the potential of plasma transferred arc coatings for the protection and refurbishment of hydraulic turbine blades. Coatings were evaluated for the influence of plasma gas flow rate on coating dilution, geometry, hardness and microstructure. Coatings processed with the atomized stellite 6 powder feedstock showed a superior surface quality, lower dilution, better wettability and wider tracks. This study provided new information about the refurbishing of worn hydraulic turbine blades, leading to a longer service working life. 相似文献
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针对传统微束等离子弧焊中焊丝熔敷率与焊接电流不能解耦的局限,提出旁路耦合微束等离子弧焊方法.通过给外填焊丝添加一电流,使焊丝与焊枪钨极间产生一个旁路电弧,实现熔化母材热量与熔化焊丝热量的解耦,确保熔化母材电流稳定的同时提高填充焊丝的熔化速度.对旁路耦合微束等离子弧焊的熔敷率、母材热输入及焊缝成形质量进行试验研究.结果表明,该方法既保持了传统微束等离子弧焊的优点,又在提高焊丝熔敷率的同时降低母材的热输入;并在其它焊接参数保持不变时,随旁路电流的增加,焊缝的熔宽、熔深和稀释率减小,余高和成形系数增大. 相似文献
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Ultrafast thermal plasma physical vapor deposition of yttria-stabilized zirconia for novel thermal barrier coatings 总被引:1,自引:0,他引:1
Heji Huang Keisuke Eguchi Makoto Kambara Toyonobu Yoshida 《Journal of Thermal Spray Technology》2006,15(1):83-91
This research aims to develop advanced thermal plasma spraying technology for the next-generation thermal barrier coatings
(TBCs) with a high power hybrid plasma spraying system. By using thermal plasma physical vapor deposition (TP-PVD), various
functional structured yttria-stabilized zirconia (YSZ) coatings were deposited. Parameters, such as powder feeding rate, hydrogen
gas concentration, and total mass flow rate of the plasma gas, were optimized, and their influences on the evaporation of
YSZ powder were investigated. Ultrafast deposition of a thick coating was achieved at a rate of over 150 μm/min. The deposited
porous coating has a low thermal conductivity of 0.7W/mK and the dense coating with interlaced t′ domains possesses a high nanohardness of 27.85 GPa and a high reflectance. These characteristics show that the TP-PVD technique
is a very valuable process for manufacturing novel TBCs. 相似文献
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The processing technique is decisive for the characteristics of a coating. This is because the heat supply, which depends on the technique and on the parameters, has an influence on the dilution and the solidification rate. In alloys with low metallurgical complexity, the effect of processing with deposition techniques that give a higher cooling rate may be translated into refining of the microstructure. A more refined microstructure is expected to result in higher mechanical strength of the coating. However, in the deposition of alloys that are more complex metallurgically this does not always occur, because the high cooling rate may suppress formation/precipitation of phases responsible for strength. The influence of processing on the microstructure and hardness of coatings of alloy Colmonoy-6® was assessed in this study. The alloy was processed by plasma transferred arc and high-power diode laser on plates of AISI 304 with two levels of dilution. In both cases, good-quality, defect-free coatings were obtained. Increase in Fe content (dilution) and different cooling rates result from processing with different parameters and techniques. This leads to significant changes in microstructure and hardness of the coatings, associated with the distribution, morphology and chemical composition of the carbides and particularly of the borides. 相似文献
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A. Gjevori J.W. Gerlach D. Manova W. Assmann E. Valcheva S. Mändl 《Surface & coatings technology》2011
By inserting an auxiliary rf plasma source in an experimental setup for depositing TiO2 thin films with a cathodic vacuum arc and high voltage pulses, i.e. metal plasma immersion ion implantation & deposition (MePIIID), it is shown that this auxiliary plasma source can increase the growth rate at low gas flow ratios only but not increase the oxygen/titanium ratio. It can be surmised that the plasma source creates activated oxygen species which are otherwise supplied from collisions of the titanium plasma stream with the background gas at higher pressures. 相似文献
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A study on consumable aided tungsten indirect arc welding 总被引:1,自引:0,他引:1
A consumable aided tungsten indirect arc welding method has been studied. This method is different from the traditional TIG welding because it introduces an MIG welding torch into the traditional TIG welding system. An indirect arc is generated between the consumable electrode of the MIG welding torch and the tungsten electrode of the TIG welding torch, but not generated between the tungsten electrode of the welding torch and the base metal. Welding current flows from the consumable electrode to the tungsten electrode in the free-burning indirect arc. The consumable aided tungsten indirect arc welding not only rapidly melts the welding wire but also effectively restrains the excessive fusion of the base metal. The welding experiment and the theoretical analysis confirm that this method can obtain a high deposition rate and a low dilution ratio during the welding process. 相似文献
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Laser deposition with wire offers saving potentials over powder based systems. These include a cleaner processing environment, reduced economic and environmental cost of producing the wire, better surface finish and higher material deposition rates. This technique is rapidly finding applications for the manufacture and repair of high value components. For the first time, the deposition of Inconel 625 wire for single tracks at varying processing parameters using a 2-kW Ytterbium doped fibre laser has been investigated. A process map predicting the process characteristics in terms of wire dripping, smooth wire transfer and wire stubbing at different cladding conditions has been developed. Track geometrical characteristics including aspect ratio and contact angle were evaluated using surface profilometry and optical microscopy. Scanning electron microscopy equipped with energy dispersive X-ray spectroscopy was used to determine the dilution ratio (%) of the tracks. Wire deposition volume per unit length of track and energy per unit length of track were found to be key parameters influencing both the process and track geometrical characteristics. Aspect ratio and dilution ratio showed positive dependency whereas contact angle showed negative dependency on energy per unit length of track. Conversely, material deposition volume per unit length of track varied directly with contact angle but inversely with aspect ratio and dilution ratio (ranging from 0% to 24%). Processing conditions at which a combination of favourable single track properties including low contact angle (<80°), minimal dilution ratio (5–13%) and high surface quality were achieved are presented. These properties are required for depositing overlapped tracks of good surface finish, minimal dilution and free of inter-run porosity. 相似文献
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当前主流的镀层沉积技术中,电弧离子镀因镀料熔融喷溅脱靶致镀料中夹杂微米尺度高温颗粒,易使镀层表面粗糙和基体高温损伤;直流磁控溅射因镀料碰撞溅射脱靶致离化率低,易使镀层厚度不均和组织疏松。为解决以上技术缺点,依据气体放电等离子体物理学知识,采用新型阶梯式双级脉冲电场诱发阴极靶材与阳极腔体间气体微弧放电,依靠微弧放电后产生的高密度等离子体,增强Ar+对靶面的轰击动能和靶面产生的焦耳热,实现镀料由碰撞溅射脱靶向热发射脱靶的转变,并以此提高镀料的离化率,达到改善镀层结构的目的。实验结果表明:双级脉冲电场诱发的气体微弧放电呈现出耀眼白光,而靶面形貌则表现出高低起伏的凹坑和水流波纹,其靶面形貌不同于镀料碰撞溅射脱靶后的多边形凹坑,说明靶面局部区域的镀料以热发射方式脱靶。同时,在双级脉冲电场下制备的TiN镀层具有较为致密的组织结构,沉积速率可达51nm/min。 相似文献
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高功率脉冲磁控溅射技术虽能实现提高镀料离化率以增强镀层力学性能的设计初衷,但其极低的沉积速率降低了工作效率,阻碍了该技术产业化的成功推广。因此,期望在达到镀料高离化率的同时,兼顾高速沉积是本研究的主要目的,为此本文提出一种创新性的研究思路,利用自主研发的双级脉冲电场,通过分别调控两个脉冲阶段的电场参量引发阴极靶面气体放电由辉光向弧光转变,借助弧光放电产生的高密度等离子体,增强靶面氩离子的碰撞动能和金属靶材产生的焦耳热,诱发镀料以高离化率、高产额的热发射方式脱离靶材。实验结果表明:在持续提高铜靶和钛靶的靶电流密度时,阴极靶材与阳极腔体间的伏安特性会由正比例的递增关系转变为反比例的递减关系,这说明气体放电会由辉光放电向弧光放电转变,并以此诱发镀料由碰撞溅射脱靶转变为溅射+热发射脱靶。实验以钛靶作为研究对象,采用双级脉冲电场在提高钛靶电流密度时,靶面形貌由具有阶梯状直线条纹的多边形凹坑结构转变为具有直线条纹的多边形凹坑和水流波纹状的圆形凹坑的混合结构,说明此时靶面镀料的脱靶方式除典型的碰撞溅射外,已逐渐向碰撞溅射加热发射双重脱靶方式转变,镀层的沉积速率也由6 nm/min大幅增大至26 nm/min。 相似文献
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采用特殊的等离子体技术成功研制出适合于金刚石涂层工具工业化生产的中试设备-强电流直流伸展电弧等离子体CVD-500型中试设备。单腔体沉积的沉积工件数量在100支以上;对该设备的沉积均匀性进行了系统的研究,位于等离子体扩散区同一柱面不同位置沉积的金刚石形貌及质量均匀、一致,涂层厚度的不均匀度在±3.5%的范围内;同一沉积试件不同位置处的金刚石形貌及质量稍有差别,但均在许可范围之内,涂层厚度的不均匀度在±2%的范围内;等离子体的扩散区的径向6 cm~8cm,轴向距阳极7 cm-19cm的范围为该设备的有效沉积区域。 相似文献
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Tri-arc双丝电弧焊堆焊工艺研究 总被引:1,自引:0,他引:1
采用三电弧双丝电弧焊,利用耐磨堆焊Fe-Cr-C-B系药芯焊丝作双丝,在Q235钢表面制备不同焊接工艺参数堆焊层,分析堆焊层熔合比、组织结构及耐磨性。结果表明:三电弧双丝药芯电弧焊堆焊可在较大范围调整焊接参数,获得较小的焊缝熔深、较低稀释率和较高的熔敷效率,耐磨性优异;当三电弧电流为150 A、电压30 V、焊丝伸出长度15 mm、送丝速度6 m/min、脉冲频率70 Hz时,堆焊层熔合比为0.07,堆焊层HRC为65,磨损量最小,耐磨性优良。 相似文献