Microstructural Evolution During Welding of High Si Solution-Strengthened Ferritic Ductile Cast Iron Using Different Filler Metals

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2024-07, Vol.55 (7), p.2309-2323
• Main Authors: Alizadeh-Sh, M., Fæster, S., Farahani, E. B., Sarhadi, A., Tiedje, N. S., Eder, M. A., Danielsen, H. K.
• Format: Article
• Language: English
• Subjects: Base metal; Bead on plate welding; Cast iron; Cementite; Characterization and Evaluation of Materials; Chemistry and Materials Science; Diffusion welding; Evolution; Filler metals; Heat affected zone; Heat treating; Intermetallic compounds; Iron compounds; Martensite; Materials Science; Melting; Metallic Materials; Microhardness; Microstructure; Nanotechnology; Nickel base alloys; Nickel compounds; Nodular iron; Original Research Article; Solidification; Solution strengthening; Structural Materials; Surfaces and Interfaces; Thin Films; Wire
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-024-07399-4

The paper deals in depth with characterizing bead-on-plate welds on EN-GJS-500-14 base metal, utilizing two filler metals: a pure Ni wire and a NiFe wire containing 45 wt pct Ni. The welds were conducted using the same heat input to ensure comparability in microstructure analysis. The microstructural observations were carried out using optical and scanning electron microscopies, X-ray tomography, X-ray diffraction analysis, and microhardness testing. Thermodynamic simulations using the non-equilibrium Scheil solidification model provide insights into the solidification process and the underlying metallurgical factors associated with the observed microstructural evolution. The observations revealed that the pure Ni wire deposited a softer fusion zone with graphite precipitation, while cementite precipitated in the fusion zone of NiFe alloy. The formation of martensite structures with different morphologies was the predominant microstructural evolution in the heat-affected zone of both welds. The partially melted zone of the pure Ni weld is narrower than the NiFe weld because more diffusion of Ni avoids widening the brittle structures in the partially melted zone. An unmixed zone in the form of a peninsula was exclusively observed in the fusion zone of the NiFe weld because of inadequate diffusion of Ni into the liquified materials along the fusion boundary.