等离子熔覆高硼Fe-Cr基涂层的组织与性能

采用常压弧光等离子体在碳钢表面制备高硼Fe-Cr基合金涂层.采用扫描电镜、X射线衍射仪、能谱仪、显微硬度计等对熔覆层的相、组织和显微硬度进行了分析.结果表明,熔覆层中的主晶相是γ-Fe(Ni),Fe_2 B;熔覆层由大量等边L形、长条状Fe_2 B初晶相、γ-Fe(Ni)与硼化物的共晶体组成,共晶体呈片层状、菊花状.熔覆层与基体呈冶金结合,界面组织呈扇形共晶、树枝晶等形态.熔覆层的硬度为1 100～1 400 HV0.2,约是基体硬度(290 HV0.2)的4倍.靠近熔覆层的基体由于淬火效应硬度提高到600 HV0.2左右.

Abstract：

A harden coating of Fe-Cr based alloy, containing high boron, was produced on midium carbon steel plate by plasma cladding process. The phases, microstructures and microhardness of the cladding coating were investigated by Scanning Electron Microscopy ( SEM ) , X-ray Diffractometer ( XRD ) , Energy-dispersive Spectroscopy (EDS) and microhardness tester. The chief phases of the cladding coating are γ-Fe(Ni)and Fe_2B. The microstructures of cladding coating were consisted of Fe_2B with shapes of equilateral L or lath and eutectic of γ-Fe(Ni)and borides, and the eutectic presented itself with lamella or rosette shape. An excellent metallurgical interface between the coating and the substrate appeared. The micro-structures of the layer near the interface exhibit fan-shaped or dendritic structure. The microhardness value of the cladding coating was 1 100 - 1 400HV_(0.2) and was about 4 times of the substrate (290HV_(0.2)). The microhardness of the substrate near the interface increased to 600HV_(0.2) because of quenching.     

钛合金表面反应电火花沉积TiN/Ti复合涂层

利用自制的电火花沉积充气密闭式保护装置和DZ-1400型电火花沉积/堆焊机,以工业纯钛TA2为电极,以工业纯氮为保护气和反应气,在TC4钛合金表面上反应电火花沉积制备了TiN/Ti复合涂层.利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、X射线光电子仪(XPS)分析了涂层的组织、物相和元素组成,利用显微硬度计测定了涂层的显微硬度,利用自制磨损试验装置对比涂层与淬火W18Cr4V高速钢的磨损性能.结果表明,涂层与基体形成良好的冶金结合,涂层主要由钛和反应合成的TiN组成,涂层的平均显微硬度可达1 388 HV0.1,是基体硬度的6倍以上,涂层具有较好的耐磨性.

Abstract：

TiN/Ti composite coating was deposited on TC4 titanium alloy substrate with the self-made special gas-filled-closed electric-spark deposition device and electric-spark deposition machine modeled DZ-1400, the industry pure titanium (TA2) was used as electrode and the industry pure nitrogen gas as shielding and reacting atmosphere. The microstructures, interfacial behavior, phase and element in the coatings were investigated by scanning electronic microscope, X-ray diffraction and X-ray photo spectrum. The microhardness of coatings was tested and its wear-resistance property was tested by the self-made abrasion machine and compared with Wi8Cr4V rapid steel treated by quenching. The results show that an excellent bonding between the coating and substrate is ensured by the strong metallurgical interface. The coatings are mainly composed of Ti and synthesized TiN. The highest microhardness of coating reaches to 1 388 HV0. 1, which is six times higher than that of the substrates. Wear resistance of the coatings is excellent.     

Microstructure and wear-resistant properties of NiCr–Cr_3C_2 coating with Ni45 transition layer produced by laser cladding

NiCr–Cr3C2 metal–ceramic composite coating is commonly produced on metal substrate by laser cladding to be used as wear-resistant coating under medium- or high-temperature working conditions.The coating has high hardness, generally over three times that of the substrate.In order to make the hardness increase gradually from substrate to coating surface, the nickel-based alloy Ni45 was chosen as the transition layer and Ni Cr–Cr3C2 coating was indirectly cladded on 20Cr2Ni4 A substrate.Microstructure and composition of the coating were characterized by scanning electron microscope(SEM), energy-dispersive spectroscopy(EDS) and X-ray diffraction(XRD).Microhardness of the cross section of the coating was measured.Friction and wear behavior of Ni Cr–Cr3C2coating and substrate were investigated through sliding against the Si C ball at 20, 100 and 300 °C.The morphologies of worn surfaces were analyzed by SEM and EDS.The results show that the hardness of Ni45 transition layer is between that of the substrate and Ni Cr–Cr3C2coating, which avoids hardness jump and stress concentration of the coating.Ni Cr–Cr3C2coating contains hard phases of Cr3C2 and Cr7C3which enhance the wear resistance.With thetemperature increasing, friction coefficient and wear rate of the substrate increase significantly.Compared with the substrate, Ni Cr–Cr3C2coating has lower friction coefficient and wear rate at 100 and 300 °C, which verifies the good wear resistance of NiCr–Cr3C2 coating.     

激光冲击对电火花修复SiCp/Cu复合材料裂纹力学性能的影响

利用钕玻璃激光冲击强化设备对经电火花堆焊修复的 SiCp/Cu 复合材料裂纹进行了激光冲击强化处理,研究了激光冲击强化处理对电火花堆焊修复裂纹的影响.用 X 射线应力仪测定了沿垂直焊缝方向表面残余应力的分布状况,用微机控制电子万能试验机测量拉伸性能,用显微硬度计测试了焊缝表面的显微硬度.结果表明,当激光脉冲能量为 35J,激光光斑直径为 5mm 时,激光冲击强化处理可以减小或消除焊缝表面残余拉应力,提高经电火花堆焊修复的 SiCp/Cu 复合材料裂纹试样的抗拉强度,还可以提高堆焊焊缝表面显微硬度.

Abstract：

The crack of SiCp/Cu composite weld restored by electro-spark overlaying was processed by Nd: glass laser, and effects of laser shock processing on the electro-spark overlaying weld crack were analyzed. Surface welding residual stress distribution alone the transverse direction of the weld was investigated by X-ray diffraction techniques, the tensile strength of the weld was investigated by strength test, and the micro-hardness distribution of the weld surface was measured with a micro-hardness tester. The results show that when laser power is 35 J and laser spot diameter is 5 mm, the laser shock processing can reduce the welding residual stresses,which even change from the tensile stress into compressive stress,and improve the tensile strength and the hardness of SiCp/Cu composite weld restored by electro-spark overlaying.     

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.     

氩弧熔覆WC增强镍基涂层的组织与性能分析

利用氩弧为热源,以 Ni60A 和铸造 WC 混合合金粉末为原料,采用预置法在Q235 普通碳素钢上制备了 WC 增强镍基涂层,用 XJP-200 型金相显微镜和 KyKy-2800 型扫描显微镜观察了熔覆层的结合状况和组织结构,用 MH-6 型硬度计测量了熔覆层截面显微硬度,用 MPX-200 磨损试验机对比了熔覆层和 65Mn 淬火回火钢的耐磨性并分析了熔覆层的耐磨机理.结果表明,以氩弧为熔覆热源制备的熔覆层,组织致密均匀、强韧性高、耐磨性好且与基体呈冶金结合,熔覆层可以用于零件表面的耐磨强化.

Abstract：

In order to improve the wear-resistance properties of carbon steel, WC particulate reinforced Ni-based composite coatings was fabricated on Q235 steel substrate by using argon-arc cladding and using the mixed-powders of Ni60A and cast tungsten carbide powder as the raw materials. The bonding state and microstructure of the coatings were observed with metallography microscope model XJP-200 and scanning electronic microscope model KyKy2800, the microhardness of the cross section of the coatings was tested with the hardmeter of model MH-6, the abradability of cladding coating to 65Mn steel quenched and tempered was used to compare wear tester model MPX-200, and the abrasion mechanism of the claddings was analyzed. The results indicate that microstructure of the claddings is uniform, continuous and defect-free; the strength,toughness and wear resistance of the claddings are excellent; bonding between the coating and the carbon steel substrate is ensured by the strong metallurgical interface. The claddings can be used to strengthen the surface of the wear-resistant parts.     

工艺参数对堆焊层组织性能的影响

采用碳弧堆焊设备制备 Cr-B-Ni-V 系耐磨合金,在制备过程中加入直流横向磁场.外加磁场将与电弧、熔池相互作用形成电磁搅拌现象,细化堆焊层金属的组织,影响硬质相的形核及分布,进而提高堆焊层的综合力学性能.通过对堆焊层进行硬度、磨损试验以及显微组织分析,研究堆焊速度、磁场强度对堆焊层金属的硬度和耐磨性的影响规律.结果表明,堆焊速度应与磁场电流配合使用,才能使堆焊层的性能得到充分改善;当堆焊速度为 12cm/min,磁场电流为 3A 时,堆焊层的硬度得到最大值,而磨损量达到最小值,其具体数值硬度为 54.4 HRC,磨损量为 0.0335 g.

Abstract：

In order to refine the structure of deposited metal and control the morphology and distribution of hard phase in surfacing deposit, DC transverse magnetic field was applied to the carbon arc surfacing of Cr-B-Ni-V iron based alloy system. The influence of magnetic intensity and surfacing speed on degree of hardness and wearing resistance was studied through analyzing the hardness, wearing and microstructures of the surfacing deposit. The results show that good match of magnetic field intensity and surfacing speed can improve the properties of surfacing deposit; the optimal values of surfacing deposit are 54.4 HRC and Δm = 0.033 5 when magnetic field current is 3 A, surfacing current is 180 A and surfacing speed is 12 cm/min.     

Characterization of diffusion-bonded joint between Al and Mg using a Ni interlayer

Aluminum and magnesium were joined through diffusion bonding using Ni interlayer. The microstructure and mechanical performance of the Al/Ni/Mg joints at different temperatures was investigated by means of scanning electron microscope(SEM), electro-probe microanalyzer(EPMA), X-ray diffraction(XRD), Vickers hardness testing, and shear testing. The results show that the addition of Ni interlayer eliminates the formation of Mg–Al intermetallic compounds and improves the bonding strength of the Al/Mg joints. The Al/Ni/Mg joints are formed by the diffusion of Al, Ni and Mg, Ni. The microstructure at the joint interface from Al side to Mg side is Al substrate/Al–Ni reaction layer/Ni interlayer/Mg–Ni reaction layer/Mg substrate multilayer structure. The microhardness of the Mg–Ni reaction layer has the largest value of HV 255.0 owing to the existence of Mg_2Ni phase.With the increase of bonding temperature, the shear strength of the joints increases firstly and then decreases.The Al/Ni/Mg joint bonds at 713 K for 90 min, exhibiting the maximum shear strength of 20.5 MPa, which is greater than that of bonding joint bonded directly or with Ag interlayer. The fracture of the joints takes place at the Mg–Ni interface rather than the Al–Ni interface, and the fracture way of the joints is brittle fracture.     

Corrosion behavior of a CuCrNiAl alloy in the presence of NaCl deposit

The corrosion behavior of a CuCrNiAl alloy with NaCl deposit at 700 and 900℃ was studied by means of metalloscope, XRD, SEM/EDX, and thermogravimetric analysis. The results indicated that the corrosion of the CuCrNiAl alloy beneath the NaCl deposit is severe; the corrosion production is loose and easy to scale off; the Cr phase is easier to erode than the Cu phase, and the contents of Cu and Cr decrease when the content of Ni increases in the matrix of the alloy beneath the corrosion region. The effects of distortion on the corrosion of the CuCrNiAl alloy were discussed, and the acceleration mechanisms of NaCl on the corrosion were also discussed.     

Alloying Effect Of Ni And Cr On The Ttability Of Copper On W Substrate

By the sessile drop technique, the wettability of Cu/W systems with the additions of Ni and Cr has been studied under vacuum atmosphere. Effects of Ni and Cr contents and wetting temperatures on the wettability and the wetting mechanisms of copper on W substrate have been investigated in detail. The results show that the wetting angles of Cu on the W substrate are decreased with an increase in the content of Ni or Cr, and also decrease with raising the wetting temperatures. SEM, EPMA, and X-ray diffraction have been used to analyze the interracial characteristics of the CuNi/W and CuCr/W systems. The results reveal that there is a transition layer about 2- 3μm in the interface of Cu-4.0 wt pct Ni/W, in which the interrnetallic phase Ni4W is precipitated. As to CuCr/W system, no reaction occurs at the interface. The two factors are that the contents of Cr and Ni and the infiltration temperature must be chosen appropriately in order to control the interfacial dissolution and reaction when the Cu- W alloys are prepared by the infiltration method.     

安徽省巢湖市尖山铁矿北段地质特征及找矿标志

安徽省巢湖市尖山铁矿北段位于肥东新太古代—早元古代变质岩区浮槎山—大康集复背斜中段南东翼,铁矿体主要赋存于大横山岩组斜长片麻岩中,属沉积变质型铁矿床.基础地质和成矿作用研究工作揭示了该区具有寻找沉积变质型铁矿的良好前景,但本区铁质来源不够丰富,而且地壳振荡运动频繁,以致矿体范围较小;虽然矿层层数多,但单层薄,规模偏小....     

Rapidly Solidified Thick Nickel Base Alloy Deposit with Carbide Particles Produced by Plasma Spraying

Ni-1.5 wt.% C, Ni-1.5 wt.%C-14 wt.%Cr, and Ni-1.5 wt.%C-29 wt.%Cr alloy powders were low-pressure plasma sprayed to produce nickel-base composite deposits with dispersed carbide particles. The constituent of the as-sprayed deposit formed on a water-cooled substrate from the Ni-1.5 wt.%C alloy powder is a nickel phase that is supersaturated with carbon. The deposit heat-treated at 673 K in vacuum consists of a nickel phase, nickel carbide, and graphite. In the case of the Ni-1.5 wt.%C-14 wt.%Cr alloy powder, the as-sprayed deposit produced on a water-cooled substrate is made up of a nickel phase that is supersaturated with chromium and carbon, and subsequent heat-treatment of the deposit leads to the formation of chromium carbide and graphite. When the non-cooled substrate is used, the as-sprayed deposit consists of a nickel phase, chromium carbide, and graphite. The as-sprayed deposit formed on a non-cooled substrate from the Ni-1.5 wt.%C-29 wt.%Cr alloy powder is composed of a nickel phase, chromium carbide, and graphite.     

Rolling behaviour of steel backed spray deposited Al–Sn strip

Steel backed Al–10 wt%Sn strip has been prepared by the spray deposition of the molten Al–Sn alloy on a steel substrate, followed by rolling of the resulting composite strip. In the present paper the rolling behaviour of the composite strip at 473 K, together with the characteristics of the spray deposit have been discussed. It has been shown that the Al–Sn spray deposit is a coalesced network of particles having porosity. The particles in the network are of spherical, ligament and irregular shapes. The study shows that the composite metal strip can be rolled well at 473 K without any delamination or surface and edge cracking on the deposit layer. A rolling thickness reduction of 75% produces steel backed Al–10 wt%Sn strip having optimum properties. During rolling, densification in the deposit, deformation in the deposit and substrate, and bonding between the deposit and the substrate take place simultaneously. The mechanism of densification in the deposit layer during rolling has been discussed on the basis of the examination of the microstructure of the deposit at different stages of rolling.     

贫铀表面钛镀层的抗腐蚀性能研究

利用电化学测试技术、扫描电镜(SEM)及X射线能谱(EDS)对贫铀表面钛镀层的抗腐蚀性能进行了研究。结果表明:在50μg/gCl-的KCl溶液中,钛镀层的腐蚀电位远高于贫铀的腐蚀电位,钛镀层对贫铀是阴极性镀层,对贫铀的保护是基于其对腐蚀介质的物理屏障作用;贫铀表面完整钛镀层的极化电阻和电化学阻抗幅值远大于贫铀,腐蚀电流远小于贫铀,完整钛镀层对贫铀具有良好的抗腐蚀保护作用;贫铀表面钛镀层的腐蚀特征为局部腐蚀,由孔蚀向电偶腐蚀转变;破坏的钛镀层将加速铀基体的腐蚀。     

Rapidly solidified thick stainless cast iron alloy deposit with niobium carbide particles produced by plasma spraying

In plasma spraying process, spray material is heated, melted and accelerated by a high temperature flame. Low-pressure plasma spraying can produce rapidly solidified thick materials because alloy droplets accumulate successively on the substrate, and solidify at a cooling rate in the range of 10⁵–10⁸ ks^?1. Depending on the cooling conditions of the substrate and on the alloy composition, deposits can be produced as metastable phases or extremely fine crystalline phases. Plasma spraying is an attractive method for the production of deposits with in-situ formed fine particles. In recent years, much attention has been paid to stainless cast iron with vanadium carbide, which is attractive for use in metal molds and pump parts, due to its high wear resistance and high corrosion resistance. In the present work, stainless cast iron alloy powder was low-pressure plasma sprayed to produce stainless cast iron base alloy deposits with finely dispersed niobium carbide particles. The as-sprayed deposit and deposits obtained by heat treatment of the as-sprayed deposit had niobium carbide particles. The carbide particles in the as-sprayed deposit produced on a water-cooled substrate were finer than that in the as-sprayed deposit produced on a non-cooled substrate. With increasing heat treatment temperature up to 1273 K, the carbide particles coarsened. The as-sprayed deposit produced on a non-cooled substrate had higher hardness than the heat-treated deposits.     

INDUCTION PLASMA REACTIVE DEPOSITION OF TUNGSTENCARBIDE FROM TUNGSTEN METAL POWDER

1. IntroductionIt was reported by Smith et al.[1] and S.ith[2] that tungsten carbide and titaniumcarbide can be formed in d.c. plasma via the reactions of tungsten powder and titaniumpowder with methane, respectively Due to the characteristics of small plasma volume,short particle residence time, and lateral injection of the powders into the d.c. plasma,only a fraction of the fed-in powders were carburized. Actually the deposits are mixturesof WC and W and the composite of TiC and Ti, respe…     

Modeling and experimental verification of tubular product formation during spray forming

A mathematical model is formulated to predict the shape evolution and the final geometry of a tubular product prepared by spray forming. The effects of several important processing parameters on the shape evolution of the tube are investigated. The model is validated against experiments of spray formed large diameter tubes. The experimental and the modeling results show that there are three distinct regions in the preform, i.e., the left transition region, the middle uniform diameter region and the right transition region. The results show that the atomization parameters as and bs, traversing speed v of the substrate, the outer diameter D0 of the substrate, and the initial deposition distance d0 play important roles in the contour and the wall thickness of the spray formed tube. But the angular velocity ω of the substrate has little effect on the buildup of the deposit. After a certain time from the beginning of the process, the deposit will come into a steady growth state. In addition, an equation is provided to estimate the wall thickness of the deposit under the steady growth state based on the mass conservation.     

Role of nickel undercoat and reduction-flame heating on the mechanical properties of Cr-C deposit electroplated from a trivalent chromium based bath

In this study, a surface hardening method for Cr-C deposits using flame heating for a short period is proposed. The hardness and wear resistance behavior of as-plated and flame-heated Cr-C deposits were investigated. The Cr-C deposits were electroplated on high carbon tool steel in a bath with trivalent chromium ions. Experimental results show that Cr-C deposits with an extremely high hardness of ca. 1700 Hv can be achieved after reduction-flame heating for 1 s. Meanwhile, the wear resistance of Cr-C deposited steel was improved after flame heating. To increase the wear resistance and bonding strength of the Cr-C deposited specimen, pre-electrodeposition of a thin Ni deposit between the Cr-C deposit and the steel substrate is recommended. A Ni undercoat with a thickness of few micrometers could reduce the crack density in the Cr-C deposit and increase the bonding strength between the Cr-C deposit and the steel substrate. As determined by a microstructure study, the as-plated Cr-C deposit has an amorphous structure, but transforms to a crystalline structure after flame heating. The main hardening mechanism is a result of the precipitation of nanograined diamond membranes, which can be extracted by immersing the flame-hardened Cr-C deposit in an etching solution comprised of 33 vol.% HNO₃ and 67 vol.% HCl.     

Microstructure and corrosion resistance of Fe-Al intermetallic coating on 45 steel synthesized by double glow plasma surface alloying technology

A binary Fe-Al alloyed layer was synthesized on 45 steel by means of double glow plasma surface alloying technique. The corrosion-resisting layer prepared is composed of a sedimentary layer and a diffusion layer, with a total thickness of about 180 μm. The aluminum content of the alloyed layer shows gradual change from surface to the inside of substrate. The ideal profile is beneficial to the metallurgical bonding of the surface alloying layer with substrate materials. The microstructure of both layers consists of the Fe-Al intermetallic compound, which is FeAl with B2 structure in the sedimentary layer and Fe3Al with incompletely ordered DO3 structure in the diffusion layer. The protective film exhibits high micro-hardness. In comparison with the substrate of 45 steel, the corrosion resistance of the aluminized sample is much higher in 2.0% Na2S and 0.05 mol/L Na2SO4 + 0.5 mol/L NaCl mixed solutions.     

Critical Deposition Condition of CoNiCrAlY Cold Spray Based on Particle Deformation Behavior

Previous research has demonstrated deposition of MCrAlY coating via the cold spray process; however, the deposition mechanism of cold spraying has not been clearly explained—only empirically described by impact velocity. The purpose of this study was to elucidate the critical deposit condition. Microscale experimental measurements of individual particle deposit dimensions were incorporated with numerical simulation to investigate particle deformation behavior. Dimensional parameters were determined from scanning electron microscopy analysis of focused ion beam-fabricated cross sections of deposited particles to describe the deposition threshold. From Johnson-Cook finite element method simulation results, there is a direct correlation between the dimensional parameters and the impact velocity. Therefore, the critical velocity can describe the deposition threshold. Moreover, the maximum equivalent plastic strain is also strongly dependent on the impact velocity. Thus, the threshold condition required for particle deposition can instead be represented by the equivalent plastic strain of the particle and substrate. For particle-substrate combinations of similar materials, the substrate is more difficult to deform. Thus, this study establishes that the dominant factor of particle deposition in the cold spray process is the maximum equivalent plastic strain of the substrate, which occurs during impact and deformation.