Influences of different filler metals on electron beam welding of titanium alloy to stainless steel

Electron beam welding experiments of titanium alloy to stainless steel were carried out with different filler metals, such as Ni, V, and Cu. Microstructures of the joints were examined by optical microscopy, scanning electron microscopy and X-ray diffraction analysis. Mechanical properties of the joints were evaluated according to tensile strength and microhardness. As a result, influences of filler metals on microstructures and mechanical properties of electron beam welded titanium-stainless steel joints were discussed. The results showed that all the filler metals were helpful to restrain the Ti-Fe intermetallics. The welds with different filler metals were all characterized by solid solution and interfacial intermetallics. For each type of the filler metal, the type of solid solution and interfacial intermetallics depended on the metallurgical reactions between the filler metals and base metals. The interfacial intermetallics were Fe2Ti＋Ni3Ti＋NiTi2, TiFe, and Cu2Ti＋CuTi＋CuTi2 in the joints welded with Ni, V, and Cu filler metals, respectively. The tensile strengths of the joints were dependent on the hardness of the interfacial intermetallics. The joint welded with Ag filler metal had the highest tensile strength, which is about 310 MPa.

Effect of Interface Form on Creep Failure and Life of Dissimilar Metal Welds Involving Nickel-Based Weld Metal and Ferritic Base Metal

For dissimilar metal welds(DMWs)involving nickel-based weld metal(WM)and ferritic heat resistant steel base metal(BM)in power plants,there must be an interface between WM and BM,and this interface suffers mechanical and microstructure mismatches and is often the rupture location of premature failure.In this study,a new form of WM/BM interface form,namely double Y-type interface was designed for the DMWs.Creep behaviors and life of DMWs containing double Y-type interface and conventional I-type interface were compared by finite element analysis and creep tests,and creep failure mechanisms were investigated by stress-strain analysis and microstructure characterization.By applying double Y-type interface instead of conventional I-type interface,failure location of DMW could be shifted from the WM/ferritic heat-affected zone(HAZ)interface into the ferritic HAZ or even the ferritic BM,and the failure mode change improved the creep life of DMW.The interface premature failure of I-type interface DMW was related to the coupling effect of microstructure degradation,stress and strain concentrations,and oxide notch on the WM/HAZ interface.The creep failure of double Y-type interface DMW was the result of Type IV fracture due to the creep voids and micro-cracks on fine-grain boundaries in HAZ,which was a result of the matrix softening of HAZ and lack of precipitate pinning at fine-grain boundaries.The double Y-type interface form separated the stress and strain concentrations in DMW from the WM/HAZ interface,preventing the trigger effect of oxide notch on interface failure and inhibiting the interfacial microstructure cracking.It is a novel scheme to prolong creep life and enhance reliability of DMW,by means of optimizing the interface form,decoupling the damage factors from WM/HAZ interface,and then changing the failure mechanism and shifting the failure location.

Inclusion behavior and microstructure of weld metal with Ce in twin wire high heat input submerged-arc welding

In this study,the welding thermal cycle curve exhibited two temperature peaks in high heat-input twin-wire separate-pool submerged-arc welding and coarse-grained heat affected zone existed in the welded joint. The inclusions of primary weld metal and coarse-grained heat affected zone of Ce-added SAW should be Al_2O_3,MnO,SiO_2,TiO,Ce_2S_3,CeS,Ce_2O_2S and Ce_2O_3. Under the effect of welding thermal cycle,oxy-sulfides inclusions of Ce,the diameter of which was less than 2. 0 μm,slightly grew larger,but the composition and type of the inclusions didn't change. The microstructure of the large heat input weld metal had acicular ferrite that Ce oxide sulphide particles induced nucleation and proeutectoid ferrite. In the coarse-grained heat affected zone of weld metal,home-position precipitation of acicular ferrite and sympathetic acicular ferrite were both observed. It was supposed that previous crystal cells of acicular ferrite in austenite grain promoted home-position precipitation of acicular ferrite. Meanwhile,sympathetic acicular ferrite tended to nucleate at the primary acicular ferrite grain boundaries,where high dislocation density was located,and grew inside the neighboring carbon-depleted austenitic regions. The granular bainite nucleated in the austenitic zone with high carbon content close to acicular ferrite and sympathetic acicular ferrite.

Experimental Study on Metal Transfer and Welding Spatter Characteristics of Cellulose Electrode

Welding spatter cause many problems during the welding process and this issue is particularly important for cellulose electrode welding. The hot flying spatter balls often deteriorate the working environment, and decrease the welding efficiency. Many factors affect the welding spatter, and metal transfer behavior is one of the main factors. Many studies concerning the spatter mechanism in arc welding process were made; most of them focused on the solid wire welding and the study on cellulose electrode is rarely reported. In this paper the metal transfer behavior and the weld spatter characteristics of three commercial cellulose electrodes were studied experimentally by using a high speed camera for visually capturing the metal transfer. The relationship between the metal transfer and the welding spatter was analyzed experimentally by comparing the spatter loss coefficient, which is for quantitative evaluation of welding spatter, with the statistical analysis of the large droplet transfer mode. The results showed that short circuiting transfer, large droplet spray transfer, fine droplet spray transfer and explosive transfer govern the metal transfer modes in cellulose electrode welding. Weld spatter occurred mainly in the deflection of large droplet process, explosive transfer process and fine droplet spraying process. Different metal transfer modes lead to different spatter. The deflection of large droplet and explosive transfer are the main factors of the spatter formation. Minimizing the droplet size and reducing the deflection of large droplet and explosive transfer leads to the reduction the amount of spatter in cellulose electrode welding.

Underwater Laser Welding/Cladding for High-performance Repair of Marine Metal Materials:A Review

With the rapid developments of marine resource exploitation,mounts of marine engineering equipment are settled on the ocean.When it is not possible to move the damaged equipment into a dry dock,welding operations must be performed in underwater environments.The underwater laser welding/cladding technique is a promising and advanced technique which could be widely applied to the maintenance of the damaged equipment.The present review paper aims to present a critical analysis and engineering overview of the underwater laser welding/cladding technique.First,we elaborated recent advances and key issues of drainage nozzles all over the world.Next,we presented the underwater laser processing and microstructural-mechanical behavior of repaired marine materials.Then,the newly developed powder-feeding based and wire-feeding based underwater laser direct metal deposition techniques were reviewed.The differences between the convection,conduction,and the metallurgical kinetics in the melt pools during underwater laser direct metal deposition and in-air laser direct metal deposition were illustrated.After that,several challenges that need to be overcame to achieve the full potential of the underwater laser welding/cladding technique are proposed.Finally,suggestions for future directions to aid the development of underwater laser welding/cladding technology and underwater metallurgical theory are provided.The present review will not only enrich the knowledge in the underwater repair technology,but also provide important guidance for the potential applications of the technology on the marine engineering.

Analysis of metal transfer during electron beam welding with filler wire

The metal transfer mode of electron beam welding （EBW） with filler wire was studied experimentally. The spatial position between the electron beam and the filler wire was defined. Basing on the charge coupled device （CCD） visual sensing system, the metal transfer mode of filler wire was investigated. The results showed that there were five transfer modes during EBW process due to different wire feed rates and spatial positions between beam and filler wire, such as short-circuiting mode, molten metal bridge mode, small droplet mode, big droplet mode and mixed mode. By comparing the weld appearance of different transfer modes, the molten metal bridge transfer was proved to be the best transfer mode.

Effect of heat input and filler metals on weld strength of gas tungsten arc welding of AISI 316 weldments

The present work investigates the effect of filler metals and heat input on weld bead geometry and mechanical properties of alloy316 welded by using GTAW.ER309 L,ER316 L and ERNi Cr Mo-3 filler metals,are applied to study their effect on the weldment.Weld defects are examined using radiographic testing.The mechanical properties of welds are evaluated through uniaxial testing,hardness measuring,and bending test.The mechanical properties and cooling rate decrease with increasing heat input.Tensile strength,yield stress and percentage elongation of weldments using three fillers are determined.Best results are obtained using ERNi Cr Mo-3.Besides,weld nugget area,cooling time and solidification time increases with increasing heat input.Finally,applying bending test on weld samples,cracks,tearing and surface defects are not observed.

Feature Extraction and Dimensionality Reduction of Arc Sound under Typical Penetration Status in Metal Inert Gas Welding

Arc sound is well known as the potential and available resource for monitoring and controlling of the weld penetration status,which is very important to the welding process quality control,so any attentions have been paid to the relationships between the arc sound and welding parameters.Some non-linear mapping models correlating the arc sound to welding parameters have been established with the help of neural networks.However,the research of utilizing arc sound to monitor and diagnose welding process is still in its infancy.A self-made real-time sensing system is applied to make a study of arc sound under typical penetration status,including partial penetration,unstable penetration,full penetration and excessive penetration,in metal inert-gas（MIG） flat tailored welding with spray transfer.Arc sound is pretreated by using wavelet de-noising and short-time windowing technologies,and its characteristics,characterizing weld penetration status,of time-domain,frequency-domain,cepstrum-domain and geometric-domain are extracted.Subsequently,high-dimensional eigenvector is constructed and feature-level parameters are successfully fused utilizing the concept of primary principal component analysis（PCA）.Ultimately,60-demensional eigenvector is replaced by the synthesis of 8-demensional vector,which achieves compression for feature space and provides technical supports for pattern classification of typical penetration status with the help of arc sound in MIG welding in the future.

PULSED Nd-YAG LASER WELDING OF AN AI-SiC_p METAL MATRIX COMPOSITE

A study is presented of the laser welding behaviour of an SiC particulate re-inforced Al-alloy comPOsite using a pulsed Nd-YAG laser. The influences of laser weldingparameters of laser intensity, pulse duration and the beamjs focus position on the depth ofweld penetration as well as the size of weld bead width were investigated. A typical mi-crostructure of a weld section reveals that the three distinct zones are present. Cracks andporosity were fOund to be two major defects in laser welded metal matrix composites(MMC). These investigations have led to an optimum welding condition proposed forlaser welding of SiC partiulate reinforced aluminium alloy comPosites with minimum de-fects.

Study on chaos in short circuit gas metal arc welding process

Based on the chaos theory, an idea is put forward to analyze the short circuit Gas Metal Arc Welding （ GMAW-S） process. The theory of phase space reconstruction and related algorithms such as mutual information and so on, are applied to analyze the chaos of the GMAW-S process. The largest Lyapunov exponents of some current time series are calculated, and the results indicate that chaos exists in the GMAW-S process. The research of the chaos in the GMAW-S process can be help to get new knowledge of the process.

Failure Analysis of Dissimilar Metal Welds between Ferritic Heat Resistant Steels and Austenitic Stainless Steels in Power Plant

This study analysed the failure of dissimilar metal welds(DMWs)between ferritic heat resistant steels and austenitic stainless steels and investigated its influencing factors by means of numerical simulation,microstructure characterization and mechanical property test.Under the long-term high-temperature service condition in practical power plant,the DMW failure mode was along the interface between nickel-based weld metal(WM)and ferritic heat resistant steel,and the failure mechanism was stress/strain concentration,microstructure degradation and oxidation coupling acting on the interface.The numerical simulation results show that interface stress/strain concentration was due to the differences in coefficient of thermal expansion and creep strength,and the degree of stress/strain concentration was related to service time.The ferrite band formed at the WM/ferritic steel interface was prone to cracking,attracting the fracture along the interface.The interface crack allowed oxidation to develop along the WM/ferritic steel interface.During long-term service,the interface stress/strain concentration,microstructure and oxidation all evolved,which synergistically promoted interface failure of DMW.However,only under the long-term service of low stress conditions could trigger the interface failure of DMW.Meanwhile,long-term service would reduce the mechanical strength and plasticity of DMW.

Atomically bonding Na anodes with metallized ceramic electrolytes by ultrasound welding for high-energy/power solid-state sodium metal batteries

A solid-state sodium metal battery has cut a striking figure in next-generation large-scale energy storage technology on account of high safety,high energy density,and low cost.Nevertheless,the large interfacial resistance and sodium dendrite growth originating from the poor interface contact seriously hinder its practical application.Herein,a modified ultrasound welding was proposed to atomically bond Na anodes and Au-metalized Na_(3)Zr_(2)Si_(2)PO_(12) electrolytes associated with the in situ formation of Na–Au alloy interlayers.Thereupon,intimate Na_(3)Zr_(2)Si_(2)PO_(12)-Au/Na interfaces with a low interfacial resistance(~23Ωcm^(2))and a strong dendrite inhibition ability were constructed.The optimized Na symmetric battery can cycle steadily for more than 900 h at 0.3 mA cm^(-2) under a low overpotential(<50 mV)of Na electroplating/stripping and deliver a high critical current density of 0.8 mAcm^(-2) at room temperature.By incorporating the above interface into the solid-state Na metal battery,taking three-dimensional Na_(3)V_(2)(PO_(4))_(3) as the cathode,the full battery offers a high energy density of 291 Wh kg^(-1) at a high power density of 1860Wkg^(-1).A pouch-type solid-state sodium metal full battery based on a ceramic electrolyte was assembled for the first time,and it lit a 3 V LED lamp.Such a strategy of the ultrasound welding metalized solid-state electrolyte/Na interface by engineering the Na-Au interlayer would pave a new pathway to engineer a low-resistance and highly stable interface for high-energy/density solid-state sodium metal batteries.

Multi-objective optimization of friction stir welding parameters using desirability approach to join Al/SiC_p metal matrix composites

Silicon carbide particulate （SiCp） reinforced cast aluminium （A1） based metal matrix composites （MMCs） have gained wide acceptance in the fabrication of light weight structures requiring high specific strength, high temperature capability and good wear resistance. Friction stir welding （FSW） process parameters play major role in deciding the performance of welded joints. The ultimate tensile strength, notch tensile strength and weld nugget hardness of friction stir butt welded joints of cast A1/SiCp MMCs （AA6061 with 20% （volume fraction） of SiCp） were investigated. The relationships between the FSW process parameters （rotational speed, welding speed and axial force） and the responses （ultimate tensile strength, notch tensile strength and weld nugget hardness） were established. The optimal welding parameters to maximize the mechanical properties were identified by using desirability approach. From this investigation, it is found that the joints fabricated with the tool rotational speed of 1370 r/min, welding speed of 88.9 mm/min, and axial force of 9.6 kN yield the maximum ultimate tensile strength, notch tensile strength and hardness of 265 MPa, 201 MPa and HV 114, respectively.

EXPERIMENTAL STUDY ON METAL TRANSFER OF CELLULOSE ELECTRODE IN VERTICAL DOWN WELDING

A high-speed photographic method is mainly used to analyze metal transfer ofa cellulose covered electrode in the vertical down welding. The experimental results show that finedroplets spraying transfer and globular transfer are the dominant transfer characteristic. The largedroplet spatter, especially the upwards spatter, is a particular phenomenon. It is found that thecombination action of gas blow force, surface tension, gravitational force and electromagnetic forcelead to globular transfer. Gravitational force and electromagnetic force, which hasten big dropletspatter, should not be neglected.

Study on arc characteristics and behavior of metal transfer in pulse current flux-cored arc welding of mild steel

The variation in arc characteristics and behavior of metal transfer with the change in pulse parameters has been studied by high speed video camera during pulse current flux-cored arc weld deposition.A comparative study of similar nature has also been carried out during flux-cored arc weld deposition in globular and spray transfer modes.The effect of pulse parameters has been studied by considering their mean current and arc voltage.The arc characteristics studied by its root diameter,projected diameter and length,and the behavior of metal transfer noted by the metal transfer model and the droplet diameter have been found to vary significantly with the pulse parameters.The observation may help in understanding the arc characteristics with respect to the variation in pulse parameters which may be beneficial in using pulse current FCAW to produce desired weld quality.

Computer-based sensing and visualizing of metal transfer mode in gas metal arc welding

Using Xenon lamp lights to overcome the strong interference from the welding arc, a computer-based system is developed to sense and visualize the metal transfer in GMAW. This system combines through-the-arc sensing of the welding current and arc voltage with high speed imaging of the metal transfer. It can simultaneously display the metal transfer processes and waveforms of electrical welding parameters in real-time The metal transfer videos and waveforms of electrical welding parameters can be recorded. Metal transfers under various welding conditions have been investigated with the system developed.

Ultrasonic vibration assisted tungsten inert gas welding of dissimilar metals 316L and L415

Ultrasonic vibration assisted tungsten inert gas welding was applied to joining stainless steel 316 L and low alloy high strength steel L415.The effect of ultrasonic vibration on the microstructure and mechanical properties of a dissimilar metal welded joint of 316 L and L415 was systematically investigated.The microstructures of both heat affected zones of L415 and weld metal were substantially refined,and the clusters ofδferrite in traditional tungsten inert gas(TIG)weld were changed to a dispersive distribution via the ultrasonic vibration.The ultrasonic vibration promoted the uniform distribution of elements and decreased the micro-segregation tendency in the weld.With the application of ultrasonic vibration,the average tensile strength and elongation of the joint was improved from 613 to 650 MPa and from 16.15%to31.54%,respectively.The content ofΣ3 grain boundaries around the fusion line zone is higher and the distribution is more uniform in the ultrasonic vibration assisted welded joint compared with the traditional one,indicating an excellent weld metal crack resistance.

Metal transfer characteristics of tandem narrow gap GMAW for flat welding position

A series of experiments of tandem narrow gap GMAW for flat welding position were carried out. The arc behavior and metal transfer process were observed by a high-speed photography system. The effects of the welding parameters on the metal transfer were investigated. The results show that the arc behavior and metal transfer process of tandem narrow gap GMA W are different from these of bead-on-plate tandem GMA W. The arc behavior and metal transfer process are influenced by the distance between the two wires, the peak voltage, the pulse frequency and the peak time. With the increase of the distance between the two wires, the metal transfer mode gradually transforms from one pulse-multi droplets into one pulse-one droplet, and the average welding current increases. With the increase of the peak voltage, pulse frequency or peak time, the metal transfer mode transforms from one pulse-one droplet into one pulse-multi droplets, and the arc tends to occur between the wire and the sidewall.

Metal vapor behavior in double electrodes TIG welding

In present paper, the metal vapour behavior in double electrodes TIG welding was investigated by a numerical model, including the arc plasma and weld pool. The thermodynamic parameters and transport coefficients of the arc plasma were dependent on both the local temperature and the mass ratio of the metal vapour. A second viscosity approximation was used to formulate the diffusion coefficient of the metal vapour in the arc plasma. The temperature and flow fields together with the metal vapour concentration were simulated, and the influences of metal vapour on the arc plasma and the weld pool were analyzed. It was found that the metal vapour transport in the arc plasma was significantly influenced by the flow of the arc plasma, and the distribution of the metal vapour was more extended in the direction perpendicular to the line through the double electrodes tips. Both the arc plasma and the heat flux at the weld pool were constricted by the presence of the metal vapour, while the metal vapour had a minor effect on the total heat input to the work piece and the weld pool profile as a whole.

Laser Welding of Zr_(41)Ti_(14)Cu_(12)Ni_(10)Be_(23) Bulk Metallic Glass and Zirconium Metal

The laser bonding technology between the Zr41 Ti14 Cu12 Ni10 Be23 bulk metallic glass and zirconium metal was investigated under welding parameters of 1.3 kW and 7 m/min. The welded bead, microstructure, and micro-hardness of the welded joint were examined by Keyence, transmission electron microscopy, scanning electron microscopy, and Vickers hardness, respectively. The experimental results showed that the Zr41 Ti14 Cu12 Ni10 Be2 bulk metallic glass and zirconium metal were successfully bonded together. The Zr41 Ti14 Cu12 Ni10 Be2 in the base material zone maintained amorphous structure, and the welding fusion zone kept the hardness as high as as-received BMG. Therefore, the laser welding technology can be used to achieve successful bonding of bulk metallic glasses and crystallization metal.