Mechanical and Metallurgical Properties of CO2 Laser Beam INCONEL 625 Welded Joints

Harinadh Vemanaboina,Edison Gundabattini,Filippo Berto,Suresh Akella,Paolo Ferro,Ramesh Kumar Buddu,A C Uma Maheshwer Rao

doi:10.3390/app11157002

Abstract

In the frame of the circular economy, welding of Ni-based superalloys has gained increasing importance when applied, for instance, to repairing highly expensive components widely used in strategical sectors, such as the defense and aerospace industries. However, correct process parameters avoiding metallurgical defects and premature failures need to be known. To reach this goal, Inconel 625 butt-welded joints were produced by CO2 laser beam welding and different combinations of process parameters. The experimental investigation was carried out with three parameters in two levels with an L4 orthogonal array. Laser power, welding speed, and shielding gas flow rate were varied, and the results were reported in terms of mechanical properties, such as microhardness, tensile strength, distortion, residual stress, and weld bead geometry, and metallurgy. At a lower welding speed of 1 m/min, the full penetration was observed for 3.0 kW and 3.3 kW laser powers. However, sound welds (porosity-free) were produced with a laser power of 3.3 kW. Overall, the obtained full-penetration specimens showed a tensile strength comparable with that of the parent material with residual stresses and distortions increasing with the increase in heat input.

Highlights

Welding is a highly complex process of permanently joining metals that involves heat source movement, mass exchange, and phase and microstructure transformations that in turn affect the joint’s mechanical properties [1]
In response to the growing demand for high-performance materials by the chemical, nuclear, fuel, aerospace, marine, and petroleum-based industries that are extremely resistant to a corrosive atmosphere, highstrength nickel-based alloys are mainly used
Nickel-based materials are austenitic superalloys containing about 50% of Ni and different percentages of Fe, Cr, Mo, and Ti

Summary

Introduction

Welding is a highly complex process of permanently joining metals that involves heat source movement, mass exchange, and phase and microstructure transformations that in turn affect the joint’s mechanical properties [1]. In response to the growing demand for high-performance materials by the chemical, nuclear, fuel, aerospace, marine, and petroleum-based industries that are extremely resistant to a corrosive atmosphere, highstrength nickel-based alloys are mainly used. They combine excellent corrosion resistance with high strength at high temperatures. The fusion welding process promotes a thermo-mechanical variation of the parent metal properties; the high heat input and uncontrolled cooling rates negatively affect the microstructure of the fusion zone (FZ) and heat-affected zone (HAZ), inducing precipitation of undesirable phases, grain coarsening (in HAZ) and tensile residual stresses, among others These mentioned changes in the welded joint have a negative impact on components’

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