利用新型光纤激光作为热源, 在氩气保护下对金刚石磨粒和Ni-Cr合金钎料进行激光钎焊工艺试验。分析了激光功率和焊接速度对焊缝成形的影响, 研究了Ni-Cr合金钎料与金刚石磨粒钎焊界面微结构和生成物。结果表明, 激光功率和焊接速度对Ni-Cr合金钎料熔化程度和金刚石热损伤具有较大影响。激光功率和焊接速度均较小时, 焊缝成形一致性差。激光功率和焊接速度均较大时, 焊缝外观成形良好而金刚石磨粒底部熔化不充分易脱落。激光功率为700 W ~ 760 W, 焊接速度为0.7~1.5 mm/s, 离焦量为+18 mm时, 可以获得外观成形良好且结合强度高的钎焊缝。Ni-Cr合金钎料与金刚石磨粒之间存在一薄结合界面, 厚度约4 μm; 金刚石磨粒表面存在片状和条状的物质, XRD分析表明为Cr3C2。

Fiber laser brazing diamond grains to substrate using Ni-Cr filler alloy was carried out in an argon atmosphere. The effects of laser power and welding speed on the weld appearance were analyzed. The microstructure and compound of Ni-Cr filler alloy and diamond grains brazed interface were studied. The results show that the laser power and welding speed have a significant effect on the degree of melting of Ni-Cr filler alloy and the thermal damage of diamond. Lower laser power and welding speed made a poor weld appearance of the brazed joint. A good weld appearance was obtained when the laser power and the welding speed were larger, however, the Ni-Cr filler alloy at the bottom of the diamond grains was insufficiently melted, resulting in fall off of the diamond. When the range of the laser power was 700 W~760 W, the welding speed was 0.7 mm/s~1.5 mm/s, and the defocus value was +18 mm, the brazed joints with good weld appearance and high bonding strength were obtained. There was a thin bonding interface between the Ni-Cr filler alloy and the diamond grains, with thickness of ~4 μm. There were slice-like and acicular products on the surface of the brazed diamond grains. The result of XRD analysis indicated that the compound on the brazed diamond grains was Cr3C2.