Showing papers on "Filler metal published in 2020"

Brazing filler metals

Abstract: Brazing is a 5000-year-old joining process which still meets advanced joining challenges today. In brazing, components are joined by heating above the melting point of a filler metal placed between...

Mechanical and Microstructural Characterization of TIG Welded Dissimilar Joints between 304L Austenitic Stainless Steel and Incoloy 800HT Nickel Alloy

Abstract: In this article, the mechanical properties and microstructure of 304L austenitic stainless steel/Incoloy 800HT nickel alloy dissimilar welded joints are investigated. The joints were made of 21.3 mm × 7.47 mm tubes using the TIG process with the use of S Ni 6082 nickel filler metal. No welding imperfections were found and high strength properties of joints were obtained, meeting the assumed acceptance criteria of the product’s standards. The tensile strength of the welded joints was higher than for the joined materials (Incoloy 800HT). Macro- and microscopic metallographic tests revealed the correct morphology of the joints and the appropriate structures in their critical zones. However, differences were found in the morphologies of the zones between the weld and the base materials. In fusion boundary from the side of the Incoloy 800HT alloy, no clear outline of the fusion line was observed (type A fusion boundary), while increased grain size and an epitaxial structure were observed. In turn, in the zone: weld–304L steel, a distinct fusion line was observed with areas with an increased amount of high-temperature δ ferrite (type B fusion boundary). No precipitates were found that could reduce the resistance of the joints to intergranular corrosion. A hardness decrease (approximately 30 HV0.1) in the transition zone: austenitic steel–weld and an increase of hardness (approximately 10 HV0.1) on the opposite side of the welded joint were observed.

Evaluation of microstructural and mechanical properties of dissimilar Inconel 625 nickel alloy–UNS S32205 duplex stainless steel weldment using MIG welding

Abstract: Inconel 625 nickel alloy and UNS S32205 duplex stainless steel (DSS) were welded with ER2209 filler metal using MIG (Metal Inert Gas) welding method. The weld metal obtained by DSS filler metal was subjected to mechanical and microstructural evaluation. Toughness and hardness properties had been examined by mechanical and microstructural characterization of weld metal, fusion line, and HAZ (Heat Affected Zone) region, and precipitations were investigated by light microscopy (LM), scanning electron microscopy (SEM), and energy-dispersive spectrometry (EDS). Corrosion behavior of base metals and face and root of weld metal were examined by using potentiodynamic polarization test. Additionally, detailed elemental analysis and mapping of weld metal with both optical emission spectrometer (OES) and X-Ray spectrometer were attained. Results demonstrate a significant decrease in toughness of the welding due to the presence of Nb and Mo rich intermetallic precipitations in the Inconel HAZ and root region, although there is no significant increase in hardness. Potentiodynamic polarization test shows that the dilution-induced microstructural transformation in the root of weld has the worst corrosion resistance in the weld metal. Therefore, this dissimilar welding does not have optimum properties for neither toughness nor corrosion.

Interfacial microstructure and shear strength of TC4 alloy joints vacuum brazed with Ti–Zr–Ni–Cu filler metal

Abstract: Ti–6Al–4V alloy was successfully vacuum brazed with a commercial Ti-37.5Zr–10Ni–15Cu (wt.%) filler metal. The effect of brazing temperature and time on the microstructure and shear strength of the brazed joints were investigated. When the brazing temperature was 905 °C for 10 min, the typical interfacial microstructure of the brazed joint were a single layer of α-Ti with a high concentration of Ti, α-Ti, (Ti, Zr)2(Cu, Ni) intermetallic compound and eutectoid microstructure. Increasing the brazing temperature and time are beneficial to eliminate the (Ti, Zr)2(Cu, Ni) intermetallic compound that degrades the properties in the brazed joint. The shear strength of the brazed joint increases first and then decreases with brazing temperature, and increases with the extended holding time. The maximum shear strength of the brazed joint is 635.77 MPa at a brazing temperature of 920 °C for 30 min due to the high content of columnar α-Ti. Extending the brazing time is obviously beneficial to increasing the strength. The microstructure and shear strength of the brazed joint are highly dependent on brazing temperature and time.

Nd:YAG laser welding of dissimilar metals of titanium alloy to stainless steel without filler metal based on a hybrid connection mechanism

Abstract: In this paper, Nd:YAG laser welding of TC4 Titanium (Ti) alloy and SUS301 L stainless steel (SS) dissimilar metal material was carried out without filler metal by laser biasing. The microstructure and fracture mode of the joint were analyzed by scanning electron microscope (SEM), energy dispersive instrument (EDS), and X-ray diffractometer (XRD). The mechanical properties of the joint were evaluated by a tensile test. The results showed that when the peak temperature was 1116℃, the liquid phase existed only in the narrower region of the Ti-SS interface, and the eutectic reaction zone formed a reaction layer, which was mainly composed of β-Ti solid solution. Ti-Fe intermetallic compound (TiFe, TiFe2) was formed at the Ti alloy-SS interface by heat conduction of the unmelted Ti alloy. The TEM analysis confirmed the presence of the β-Ti and TiFe2 phases. The nucleation and growth of the reaction layer depended on the diffusion rate and atomic concentration of Ti and Fe atoms. The growth of the reaction layer could be effectively promoted by increasing the welding heat input, increasing the peak temperature of the Ti-SS interface and prolonging the reaction time. The tensile strength of the joint could be reached 336 MPa and an elongation was 0.13 %. The eutectic reaction method could control the thickness and size of the Ti-Fe intermetallic compound at the interface of the Ti alloy-SS and improve the mechanical properties of the joint.

Experimental and numerical study on microstructure and mechanical properties for laser welding-brazing of TC4 Titanium alloy and 304 stainless steel with Cu-base filler metal

Abstract: Laser welding-brazing of TC4 Titanium (Ti) alloy to 304 stainless steel (SS) has been applied using 38Zn-61Cu alloy as filler metal. Microstructures of the joints were studied using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Mechanical properties of the joints were evaluated by performing tensile tests. The temperature field and stress field distributed in laser welding based on SS-Ti alloy joint were dynamically simulated using the ANSYS in this study. A new welding process for SS-Ti alloy joint was introduced on the basis of the controlling the formation of Ti-Fe intermetallics in the joint. One process was one pass welding involving creation of a joint with one fusion weld and one brazed weld separated by remaining unmelted SS. When laser beam on the SS side was 1.5 mm, SS would not be completely melted in joint. Through heat conduction, the filler metal melted occurred at the SS-Ti alloy interface. A brazed weld was formed at the SS-Ti alloy interface with the main microstructure of (Fe, Zn)+Fe3Zn7, β-CuZn and β-CuZn + Ti2Zn3. The joint fractured at the brazed weld with the maximum tensile strength of 210 MPa. By comparing the simulation results with the corresponding experimental findings, the validity of the numerical model is confirmed.

Microstructures and mechanical properties of stainless steel clad plate joint with diverse filler metals

Abstract: Thick stainless steel clad plate is used widely in the petroleum and petrochemical industries because of its low cost and good corrosion resistance. It is generally welded by the multilayer and multipass welding process with stainless steel filler metal matched with the clad layer. In this research, the base metal of stainless steel clad plates was filled with carbon steel filler metal, and the microstructures and mechanical properties of joints with diverse filler metals were analysed and compared. The results indicate that a local hardening zone (LHZ) forms in the weld filled with the filler metals of stainless steel and carbon steel because of the formation of martensite phase in the first layer of weld with filler metal of carbon steel. The microhardness value in LHZ reaches up to 425 HV1, which is significantly higher than that of the base metal. However, the tensile strength value of joints filled with carbon steel filler metal is equivalent to that of the joints with stainless steel filler metal. The results of the side bending test indicate that the LHZ protrudes from the weld, and the crack occurs near the LHZ if the area of the LHZ on the cross section of joint is larger than 17 % of that of the whole cross section of the joint. The studied results show that it is feasible to use carbon steel filler metal to fill the base metal of carbon steel in welding of stainless steel clad plate.

Butt laser welding of TC4 Titanium alloy and 304 stainless steel with Ag-base filler metal based on a hybrid connection mechanism

Abstract: Laser welding of TC4 Titanium (Ti) alloy to 304 stainless steel (SS) has been applied using Ag45-Cu30-Zn25 alloy as filler metal. Microstructures of the joints were studied using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Mechanical properties of the joints were evaluated by performing tensile tests. The temperature field and stress field distributed in laser welding based on SS-Ti alloy joint were dynamically simulated using the ABAQUS in this study. A new welding process for SS-Ti alloy joint was introduced on the basis of the controlling the formation of Ti-Fe intermetallics in the joint. One pass welding involving creation of a joint with one fusion weld and one diffusion weld separated by remaining unmelted SS. When laser beam on the SS side was 1.6 mm, SS would not be completely melted in joint. Through heat conduction of unmelted SS, the atomic diffusion occurred at the SS-Ti alloy interface. A diffusion weld was formed at the SS-Ti alloy interface with the main microstructure of α-Cu + Fe3Zn2, AgZn3 + CuZn, Cu4Ti + Ti2Zn3 and Ti2Cu + TiCu. The joint fractured at the diffusion weld with the maximum tensile strength of 284 MPa. By comparing the simulation results with the corresponding experimental findings, the validity of the numerical model is confirmed.

Observation and analysis of metal transfer phenomena for high-current super-TIG welding process

Abstract: Super-TIG welding is a newly developed TIG welding process using C-type filler metal in TIG welding. In Super-TIG welding, C-filler can prevent the molten pool depression, which is caused by high p...

Dissimilar joining of WC-Co to steel by low-temperature brazing

Abstract: In the present study, an Ag-Cu-Zn-Cd alloy was utilized as filler metal in order to braze the cemented carbide/Cr-Mn steel joints, and the effects of brazing time and filler metal thickness on the resultant joints were investigated. The observations showed that by the increment of the holding time, the Cu-Zn (s.s) phase grows and causes the shear strength to increase. With increasing the brazing time from 5 min to 15 min (at 780 °C), the contact angle of wetting reduced from ~40° to ~ 35.5°, and the shear strength increased from ~72.5 MPa to ~93.5 MPa. The evaluation of the fracture surfaces demonstrated the presence of dimple-like morphologies for the bond made at 15 min. The results also indicated that an increase in the interlayer thickness from 60 µm to 160 µm leads to a reduction in the strength.