Experimental studies on gear-honing-tool with laser brazing film CBN
During the process of brazing cubic boron nitride (CBN) gear-honing-tool by Laser, cleaning of the gear-honing-tool and film plating CBN abrasive, and the thickness of brazing coating directly affect the quality and life of gear-honing-tool. In the paper, based on experiment the process of laser brazing CBN is summed up, the thickness interrelationship of brazing filler metal from beginning to end is obtained, the rule of laser facula's moving speed is studied on solder layer thickness and the radial change of gear tooth thickness. It is shown that the bonding among CBN, gear-honing-tool and solder can be realized by laser brazing. In order to improve quality of brazing, the moving speed of laser facula must be reduced along radial direction of gear honing tool. As to different size of CBN abrasive, the thickness of solder layer should be varied so that the bare rates of cutting edge can be ensured. The solder layer thickness should be controlled between 1.25 and 1.5 times of average size of abrasive grains. The thickness of solder layer depends on laser energy and soldering time that can be controlled by the moving speed of laser facula.
Influence of laser energy input mode on joint interface characteristics in laser brazing with Cu-base filler metal
The flange butt joints of 1 mm-thick galvanized steel sheets were brazed with CuSi3 as filler metal at different laser heating modes. The microstructures and element distributions of joint interface were investigated by SEM and EDS. The results show that there is no obvious interface layer with the circular individual beam heating and lamellar Fe-Si intermetallic compound layer is found with dual-beam laser spot heating. With the irradiation of rectangular laser spot, the joint interface layer is also formed. The layer thickness is larger than that of dual-beam brazing and the layer shape is flat so that intermetallic compounds trend to grow into cellular crystals. Moreover, the interface layer shape also depends on its position in the joint. Under the high heat input, dendritic or granular intermetallic compounds dispersively distribute in brazing seam adjacent to the interface, which is caused by the melting or dissolving of the base metal. According to the results, the brazing quality can be controlled by laser heating mode and processing parameters.
Joining silicon nitride ceramic using a composite powder as active brazing alloy
Abstract The aim of this study was to join silicon nitride ceramic using a Cu–Ti bi-metallic composite powder. The microstructure and mechanical properties obtained were similar to results obtained with conventional active brazing alloys but with different kinetics. The experimental results obtained show the potential in using the composite powder as a brazing alloy. The reaction layer produced at the ceramic/filler metal interface was composed mainly of TiN and Ti 5 Si 3 . Similar to many active ceramic brazing processes, the reaction layer was formed in two stages, where the initial step was controlled by a liquid/solid reaction, followed by diffusion controlled growth. Depending on the brazing parameter, the reaction layer thickness ranged between 4 and 12 μm. Reaction layer growth was modeled and the effective activation energy was found to be 64 kJ/mole. The four-point bending strength varied between 250 and 400 MPa, depending on joining conditions. The crack propagation mode was through the interface for low strength joints and through the ceramic for high strength joints.