Laser-induction welding of nodular grey cast iron using oscillating beam guidance-microstructural and mechanical characterization

Abstract

In the present investigation, laser-induction welding using oscillating beam guidance is employed to joint sheets of nodular grey cast iron, which typically exhibit poor weldability properties. Through non-destructive dye-penetrant testing, a reduction of more than 50% in crack density as a result of manipulted thermal cycles is identified. The microstructural and chemical characterization using scanning electron microscopy, energy dispersive X-ray spectroscopy and electron backscatter diffraction reveal the formation of brittle cementite lamellae with austenite/ferrite at the inter-lamellar spaces. The direction of beam oscillation and, thus, melt pool dynamics as well as thermal history exhibit a substantial influence on hardness and tensile properties, which are favourable for specimens welded with beam oscillation perpendicular to the traverse direction. Here, the maximum hardness of EN-GJS-400–15 specimens is reduced to around 700 HV. Yet, embrittlement and cleavage fracture originating from cold-cracks and pores within the weld metal are observed as well and emphasize the ongoing challenges of welding nodular grey cast iron.

Keywords

• Laser beam welding
• Nodular cast iron
• Laser-induction welding
• Oscillating beam guidance
• Electron microscopy
• Microstructure