Papers by Keyword: Laser Brazing

Abstract: The microstructure and mechanical properties of a joint produced by laser brazing between A5052 and AZ31 with AZ61, AZ91 and AZ125 filler metal was investigated. The effects of filler metals on joint characteristics are also discussed. Measurement of microstructural factors in the laser brazed joint revealed that increasing the laser power results in a decrease in the weld toe angle and an increase in the bead width, which indicates superior wettability. A high strength laser brazed joint can be achieved through the combination of good wettability and a thin intermetallic layer produced by a laser power of 590 W in a brazed joint with AZ125 filler metal Any further increase in power, however, results in a rapid increase in the thickness of the intermetallic compound (IMC) reaction layer. The superiority of the brazed joint with AZ125 filler metal is due to its lower melting point than that of AZ61 and AZ91 filler metal.

Abstract: The joining of ceramic to structural alloys has received much attention in recent years because of its potentially attractive properties. In the present investigation alumina which is a ceramic has been brazed with titanium alloy (Ti6Al4V) using KM72(Ag/Cu) filler material.The study has been carried out using CO₂ laser gas in argon inert atmosphere. Uniformity of the brazed joints has been observed in scanning electron micrographs. The elements and phases present at the joint interface have been characterized by EDX and XRD spectra analysis. As per the experimental observation, the phases present in the Ti6Al4V/KM72/alumina joint are Cu₃TiO₄, Cu₃Ti₂,CuO, Ti₂Cu, CuTi, and Cu₄Ti₃. The effect of brazing process parameters on the shear strength of the brazed joint has been studied and maximum shear strength observed at brazing power of 330 watts and speed 300 mm/min is 4±0.5MPa. Micro-hardness values of the brazed interface indicate that the interface is softer than the substrate.

Abstract: The purpose of this paper is to simulate the residual field of laser brazing by FEM of ANSYS. The 2-D coupled field element is elected to create finite element model. The brazing experiments have been done by means of 45steel which is the matrix and Ni-Cr solder and the residual stress of the diamond wheel has been measured by Raman method. The results of measure show that the maximum stress value is less strength of diamond. The residual stress distribution is basically identical between the results of simulation and experiment. According to this paper, it is possible to decrease the costs of study by selecting reasonable processing parameters on laser brazing.

Abstract: Joining of dissimilar metals leading to better material utilization with improved functionality encouraged the research thrust on various dissimilar material joining processes including laser brazing. This papers reports the development of laser brazing joints and their characterization for 3 mm thick Cu sheet with 3 mm thick AISI 316L stainless steel (SS) sheet in butt joint configuration using 63Ag-35.25Cu-1.75Ti active brazing foil as filler metal. Comprehensive experiments were carried out to identify the optimum processing parameters for controlled simultaneous heating of the filler metal and sh-7eets by laser beam resulting in melting of the filler metal without melting Cu and SS sheets. Using this methodology, a number of brazed joints were successfully prepared at different set of processing parameters. The brazed joints were subjected to various non-destructive (visual and dye-penetrant test) and destructive (microscopic examination, energy dispersive spectroscopy, four point bend testing etc.) characterization techniques. The results demonstrated that laser energy per unit length of 100 J/m is threshold limit for feasibility of brazing process for selected metal and thickness combination. Microscopic studies of transverse section of laser brazed joint showed full penetration across the thickness without the melting of parent metals. EDS studies showed the diffusion of filler material (Ag) more towards the Cu sheet as compared to that of SS sheet. Four point bend test showed that the alignment of laser beam-metal joint was critical for the brazing joint strength and improved joint strength was achieved when the beam was at the centre of the brazing joint. A maximum joint strength of 343.7 MPa was achieved for laser power of 550 W at scan speed of 3 mm/min.

Abstract: A new technology kind of brazed monolayer cup diamond grinding wheel was developed via laser in an argon atmosphere. Grinding performances of this kind of brazed wheel in the surface grinding of the granites were studied. The experiment results show that the normal grinding forces and wear of diamond grits become higher with the increasing of the accumulated removal volume during grinding granites process. When continuous dry grinding was employed, the grits of the brazed diamond grinding wheel fail mainly in attired wear mode other than pull-out ones in conventional electroplated and sintered diamond tools, which indicates that the strong retention of brazing alloy to the diamond grits and longer service life of this kind of wheel.

Abstract: The purpose of this paper is used Ansys to simulate the temperature field of laser brazing by FEM. The 3-D solid elements are used in FEM model, and nonlinear factors of temperature-dependent material properties are considered. The surface temperature grades have been attained, and the brazing experiment have been conducted, the results show that the wetting of Ni-Cr alloy to diamond is good. This study is useful for selecting reasonable processing parameters on laser brazing.

Abstract: With considering the geometry characteristic of laser brazing and analyzing the action features of heat source in laser brazing, an adaptive heat source mode is constructed to simulate the dynamic response of temperature field and flow field of beryllium irradiated by a moving laser. And the shape of fusion zone and thermal cycle curve calculated agree well with the experimental results, it indicate that the proposed model is appropriate and adaptive in simulating the dynamic response of melting pool. Further, influences of latent heat of fusion and butt gap on temperature field and melting pool shape is analyzed by means of the method of numerical Analysis. The results show that the effects of the latent heat are not negligible. In particular, the influence of the latent heat is more violent under moving laser beam action than under stationary laser beam. And the predicted profile of melting pool which taking butt gap into account is more close to that of experimental results.

Abstract: In order to develop new generation brazed Diamond grinding wheels, the joining experiments of Diamond super abrasive grains and medium carbon steel using the powder mixture of Ni-Cr alloy as active brazing alloy are carried out via laser in an argon atmosphere. The relevant characteristics of the special powder mixture, the microstructure of the interfacial region, which are both the key factors for determining the joining strength among the Diamond grains, the filler layer and the steel substrate, are investigated extensively by means of scanning electron microscope (SEM) and energy dispersion spectrometer (EDS), as well X-ray diffraction (XRD) analysis. The formation mechanism of carbide layers was discussed. All the results indicate that high strength bonding between diamond grits and the steel substrate has been successfully realized because the chromium in the Ni-based alloy segregated preferentially to the surface of the diamond to form a chromium-rich reaction product Cr3C2, and the bond between the alloy and the Diamond was established through the reaction product.

Abstract: Brazing diamond grits to steel substrate using Ni-based filler alloy was carried out via laser in an argon atmosphere. Thermodynamic analysis was performed in order to research the interfacial reaction mechanism of diamond and Ni-Cr alloy during high temperature brazing. Meanwhile, microstructure of the interfacial layer was experimentally detected by scanning electron microscope (SEM), energy dispersion spectrometer (EDS) and X-ray diffraction (XRD) in this paper. The results indicate that according to the thermodynamic theory the interfacial reaction has been proved feasible, and during brazing high strength bonding between diamond grits and the steel substrate has been successfully realized because the chromium in the Ni-based alloy segregated preferentially to the surface of the diamond to form a chromium-rich reaction product Cr3C2, and the bond between the alloy and the Diamond was established through the reaction product.

Abstract: Brazing diamond wheel was carried out via laser in an argon atmosphere. The interfacial microstructures among brazed diamond, the filler alloy and matrix were analyzed by scanning electron microscopy (SEM), energy dispersion spectrometer (EDS) and X- ray diffraction (XRD). The formation mechanism of carbide layers was also discussed. Finally, grinding examination of the grinding wheel was carried through. The results show that diamond can not fall off from the wheel even at heavy duty conditions.