To discuss the performance of high drill content yg18 cemented carbide laser welding . Taking cu as filling material, you can obtain good braze welding head through laser heat conduction welding. Welding the both upper sides in deep penetration laser mode.
Cemented carbide, they are divided into different grades according to a different co contents, yg18 is a kind of containing a high percentage of diamond sintering cemented carbide. The improvement of drill content have two hands relative to the low carbide drill content, on the one hand, it have more gold in the metallurgical performance attributes, on the other hand, the welding performance has gained a certain degree of improvement.
In industry field, they often require put the different types of carbide together, such as in oil exploration, drilling bit is by yg carbide 18 for the substrate, brazing multiple yg8 cemented carbide tool bit. Because the new drill carbide cutter cutting edge surface have a layer of polycrystalline diamond material, welding process wasn’t allowed polycrystalline diamond material damage which was caused by overheating of the cutting tools. And the brazing density that was caused by way of heating power is low, and it’s difficult to ensure meet the above conditions at the same time and get the weld with sufficient bonding strength. High power industrial laser which is focused laser beam provides a high power density and local rapid heating and cooling conditions, it is helpful to realize the welding of special materials. So laser with different grades, different composition of carbide welding experiments, and understand that their welding performance is of great importance.
We used containing low drill of yg8 cemented carbide of laser welding and brass as filling material ago, adopts the model of laser heat conduction welding, won a good laser braze welding head. On this basis, this paper uses laser as the welding heat source, and brass as filling material, We used 3 kw fast axial flow co2 laser c nc machine tools in the experiments. Choose thickness of 17 mm yg18 cemented carbide as the parent metal, copper as filling material, the welding process using special fixture to fix welding sample in protection cavity, adopting the thermal conductivity welding experiment, under the lower the laser power output n) and the condition of solder, welding on both sides of the cemented carbide substrate is relatively evenly heated, neither areas of hard alloy melt temperature is too high, also avoid the evaporation, evaporation of cu, molten copper has a relatively plenty of time for wetting cemented carbide. Figure 1 is yg18 cemented carbide laser braze welding head of electron microscopy morphology. Central to cu layer, two side for carbide, has formed a good brazing joint between them, in the range of the weld, have formed a similar brazing seam. Visible, as a filler material copper can be fully wetting cemented carbide. Observed under scanning electron microscopy (sem) high magnification found that due to c. And cu moderate melting, make a small amount of granular wc spread to cu layer. Figure 2 and figure 3 are on either side of the brazing seam microstructure, including color deeper part is cu layer, through analyzing its composition of micro zone, this part of wc particles in fit in small holes, so the laser power density is high, it can be in a very short period of time and melt cemented carbide which complete fusion together with cu, weld appearance as shown in figure 5. Figure 5 is the microstructure of weld bond. It can be seen that yg18 cemented carbide under the condition is small aperture laser welding and partial melting. And yg8 cemented carbide distinction does not have obvious defects in weld; On the sides of weld Hard alloy melting point vary widely between cu and filling materials, it can control the process parameters in the experiment, on the one hand, it makes the copper within the instantaneous melting fully to infiltrate carbide, the carbide substrate heated to high temperature range, enable it to better wetting by filler material, form the ideal braze welding head.
In the process of laser heat conduction welding, forming in the course of the brazing area, it have good uniformity of brazing seam. In solder cu melting at the same time, on both sides of weld hard alloy have also been adhesive co partial melting, but not the wc cemented carbide and decomposed into w and c elemental, wc grain boundaries and sharp-angled only partial meltdowns to solder and cu in short distance displacement, and Mosaic among cu layer; At the same time co, cu and a certain degree of diffusion, the diffusion distance is short. This is due to that the brazing seam formation time is short, before solder with the parent metal to fully spread, the brazing process is annulled.
In the process of deep penetration laser, laser power density is high, in the area of laser direct effect, hard alloy melt quickly, and severe fusion effect with cu. Due to the c of yg18 cemented carbide itself. Content is very high, so after melting, even after the wc particles gathered grew up, it still can form a strong combination under the influence of cu and co cementation, but it did not produce yg8 cemented carbide after melting occurs through the cracks, porosity and other serious defects. At the bottom of the hole welding area, carbide wasn’t up to melting temperature, and forming the welding similar brazing seam and the thermal conductivity, thermal conductivity in qian are on both sides of the weld and weld the spread of the similar phenomenon occurred.
3.Deep penetration in the mode, the partial melting will not have serious defects of cemented carbide, tungsten carbide can well with cu fusion together, and it is at the bottom of the weld formation and similar brazing weld thermal conductivity welding mode.