Papers by Keyword: Filler Metal

Abstract: Austenitic stainless steels tend to form chromium depletion zones during welding. The chromium combines with available carbon around the grain boundaries to produce chromium-deficient areas, thus becoming susceptible to intergranular corrosion. The sensitization phenomenon of 304 stainless steel during gas tungsten arc welding (GTAW) process has been investigated. In this experiment, there were four welded samples observed. Two welded samples were cooled in air and cooled in oil immediately after welding, respectively. Meanwhile, another two welded samples were normalized by heated to 800 and 900 °C and held for 0.5 h before cooled in air. The welded samples were analyzed using optical microscopy, scanning electron microscopy and energy dispersive microscopy (SEM-EDS), and a Vickers hardness testing machine. The results show that normalizing affects significant changes in the microstructure due to the sensitization phenomenon. It can be seen that there is more carbide deposition in the welded sample with cooled in air and welded samples which normalized by heated to 800 °C and 900 °C and held for 0.5 h before being cooled in air. Meanwhile, the sample that was cooled in oil immediately after welding showed fewer chromium carbides. Normalizing the welded samples to 800 and 900 °C and holding it for 0.5 h before cooling in air triggers the sensitization process. Sensitization looks less occur in 304 stainless steel welds which were rapidly cooled in oil.

Abstract: In general, a flux is used to braze a copper alloy. In many cases, when the molten brazing filler metal spreads in the set joint gap, vaporised flux and its residue are produced, and defects (mainly voids) are formed. Voids, which are formed on the brazed layer, cause deterioration in the strength and other properties. However, with conventional evaluation methods (e.g. ultrasonic or X-ray radiography tests), the behaviour of the molten brazing filler metal during the brazing process cannot be visually observed from the outside of the joint. Therefore, the void formation process cannot be clarified. To improve the quality of the brazed layer, it is necessary to elucidate the mechanism of void formation. The purpose of this study is to observe the behaviour of the molten brazing filler metal by performing an X-ray radiography test at the same time as brazing and to study how to reduce voids. In this study, a brass specimen was brazed with a Cu–P-based brazing filler metal. The specimen was brazed by heating in an electric furnace, and the specimen was irradiated with X-rays. The state where the molten brazing filler metal spread into the gap was photographed as the transmission image. Thereafter, the behaviour of the molten brazing filler metal was analysed.

Abstract: The work shows the main results on the development at NRNU MEPhI of rapidly quenched amorphous and nanocrystalline ribbon-type and powder brazing filler metals based on Al, Cu, Ni, Ti and Zr and their application for brazing of a wide range of materials in nuclear, thermonuclear, aerospace, automotive, aircraft and other industries: from steels, alloys and refractory metals to various ceramics without metallization of their surfaces.

Abstract: The present work focuses on the microstructural changes that occur in the partial melted zone in welds made on some cast designated alloys. The aim of the work is to improve the available data related to PMZ morphology, properties and possible mechanism involved in the final metal response. It demonstrates that for binary alloys little changes occur in PMZ; in case of a complex alloy the changes are more consistent affecting both primary and eutectic structure when interstitials are involved. It proves also that the morphology of PMZ depends on the filler metal properties.

Abstract: Diamonds films have characteristics that are interesting for many optical applications, such as transparency to ultraviolet, visible and infrared light. These applications include use in detectors and windows in processes that involve high temperatures, microelectronics applications and wear-resistant components [. Polycrystalline diamond films can be made in the vapor phase at low-pressure, relatively low temperatures and in the form of auto-supported films, using the CVD process (Chemical Vapor Deposition) [. These films have a significant number of industrial applications, but often have problems with adhesion to metallic substrates. Diamond films can be deposited directly over some metals, but other techniques, such as brazing, can be used [.

Abstract: Effect of porosity distribution in the weld metal of AA 6061-T6 with 6 mm thickness plate using two dissimilar filler metals in the gas metal arc welding (GMAW) process was investigated. This paper provides a characterization of the porosity in term of the distribution, location and size of the pores in the weldment region. The porosity characterization was made by using 3D X-Ray Computed Tomography and Scanning Electron microscope. The existing pores resulting from the cause of the filler metal in welded alloy used ER4043 (Al-5Si) was compared with the weldement used ER5356 (Al-5Mg). From this investigation, it is exhibited that the pores only distributed and located mainly at the edges and at the root of the weldment with ER5356 weld metal, however, for weldment with ER4043, the pores were mainly scattered in the centre region. The distribution and location of pores in weld metal is believed due to the effect of convections in the molten metal, solidification rate and also from the gases induced during the weld process. Apart from that, results of tensile test indicated the weldment has affected the strength and ductility of the two different fillers selected. AA6061 with ER5356 are dropped 50% in ultimate tensile strength (UTS) and 40 % in elongation; meanwhile AA6061 with ER 4043 was dropped 70% in UTS and 90% in elongation. The different principle alloying element of these two filler metals have play significant role in the distribution of porosity in AA6061 weldment and had influence the strength and ductility of the weld joint.

Abstract: AA6061 Aluminum alloy welded joint using two different filler metals were studied by using X-ray CT-Scan. The filler metals ER 4043 and ER 5356 were used in this present work in order to investigate the effect of using different filler metals on the welded joint quality of AA 6061 aluminum alloy in welded zone microstructure. Gas metal arc welding (GMAW) technique and V grove butt joint with four layers and five passes welded joint were performed. From this investigation, it is found that AA6061 with ER 4043 showed less distribution of porosity compared to AA6061 with ER 5356 welded joint confirmed by X-ray Ct-Scan. The decreasing of porosities and presence of very fine grains in weld region area with ER 5356 compared to ER 4043 will be discussed in term of microstructure analysis.

Abstract: The filler metal used during welding process is believed to play an important role on porosity formation in aluminium alloy welded. The present investigation is aimed to study the effect of different fillers ER4043 (Al-5%Si) and ER5356 (Al-5%Mg) on porosity formation of AA6061 alloy welded joints. Butt-joint welds were made on 6 mm thick plates using 21 – 22 V arc voltages by using Gas Metal Arc Welding process (GMAW). The hardness profile of each types of AA6061 welded joints for both fillers were characterized by the Vickers microhardness test. In order to study the formation and distribution of porosity, the images of analysis were obtained using the X- ray CT-Scan. It was observed that, more porosities were found in the alloy AA6061 using ER4043 compared to ER5356 filler metals with the percentage area value of porosity about 18.3 and 8.4%, respectively. The hardness profile of ER5356 and ER4043 welded materials exhibited the similar hardness pattern profile. It is proposed that Si and Mg contents in the filler metal could play significant role in the distribution of porosity. No significant effect was observed on the hardness profile for both filler metals of welded materials.

Abstract: One of the difficulties in manufacturing of sandwich honeycomb structures is the proper joining of honeycomb cores to face sheets. In this investigation, vacuum brazing process using BNi-2 brazing alloy was applied for these types of joints. Brazing cycles were performed at temperatures ranging from 1020 to 1050oC under different holding times ranging from 5 to 20 min. Three different zones were observed in the solidified braze layer. The width of each zone was altered by brazing cycle. The results showed the crucial role of boron element in the brazing alloy in wetting behavior and final products after brazing. The optimum brazing cycle was found to be 1020oC and 5 min holding time followed by heat treating the brazed samples at 600oC for 6 hrs.

Abstract: The wetting and flowing behaviors of the filler metal during laser brazing process were analyzed by the computer simulation. Two situations of the wetting and flowing during laser brazing were modelled, i.e., the metled Au-18%Ni and Ag-10%Pd filler metals on the butt joint of Inconel 600, and the melted Cu-8%Sn filler metal on the dissimilar butt joint of type 304 stainless steel to Cu. The filler metal droplet wetted and spread on the base metals and simultaneously infiltrated into the joint gap with the lapse of time. The Au-Ni and Ag-Pd filler metal infiltrated into the 0.3mm wide joint gap at the completion of brazing even in the single beam brazing. The Au-Ni filler metal did not infiltrate into the joint gap completely at the brazing clearances of 0.1-0.2mm in the single beam brazing, however, it could be filled up in the joint gap in the tandem beam brazing. The Cu-Sn filler metal wetted on the both base metals of stainless steel and Cu and filled up the 0.3mm wide joint gap when the location of preheating beam deviated in 0.5mm to Cu substrate, however, it did not infiltrate into the joint gap completely at the deviation distance of preheating beam to Cu substrate being 1.0mm. It followed that the wetting and flowing behaviors of the filler metal during laser brazing process could be predicted by the computer simulation.