A Study on Laser Beam Welding (LBW) Technique: Effect of Heat Input on the Microstructural Evolution of Superalloy Inconel 718

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Vol. 41; no. 9; pp. 2357 - 2365
• Main Authors: Odabaşı, Akın, Ünlü, Necİp, Göller, Gültekİn, Eruslu, Mehmet Nİyazİ
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01-09-2010; Springer; Springer Nature B.V
• Subjects: Alloys; Applied sciences; Characterization and Evaluation of Materials; Chemistry and Materials Science; Exact sciences and technology; Geometry; Joining, thermal cutting: metallurgical aspects; Materials Science; Metallic Materials; Metallurgy; Metals. Metallurgy; Microstructure; Nanotechnology; Power plants; Solid solutions; Structural Materials; Surfaces and Interfaces; Thin Films; Welding; Lave Phase; Electron Beam Weld; Welding; Heat Input; Welding Speed; Nickel base alloys; Superalloy; Microstructure; Laser welding; Inconel
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-010-0319-y

The effect of heat input from laser beam welding (LBW) on the microstructural evolution of superalloy Inconel 718 was investigated. LBW was carried out on 1.6-mm-thick sheets with an average grain size of 13 
μ
m (ASTM # 9.5), and four different heat inputs in the range of 74.5 mm
−1
to 126.6 J mm
−1
were used. Full penetration was achieved in all weld experiments. Microstructures of the welds were evaluated using an optical microscope and a field emission scanning electron microscope. Increasing the heat input changed the resulting weld shape from a wine glass shape to a stemless glass shape with wider surface bead widths, and the measured average dendrite arm spacing was increased from 1.06 
μ
m to 2.30 
μ
m, indicating the corresponding solidification rate in the range of 1.75 × 10
5
 K s
−1
(°C s
−1
) to 3.5 × 10
6
 K s
−1
(°C s
−1
). The welds also were free from microfissuring even at the lowest heat input trials. The Nb concentration of Laves phase for the current LBW samples was ≈20.0 wt pct. The coefficients of partition and distribution for Nb were determined to be approximately 3.40 and 0.50, respectively.