Laser welding of a W-free precipitation strengthened Co-base superalloy

A new class of W-free, precipitation strengthened Co-base superalloys has recently been developed with improved high-temperature strength while maintaining excellent oxidation and hot corrosion resistance. In this study, we report the impact of fusion welding on microstructure and properties of an a...

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Bibliographic Details
Published in:Journal of materials science 2022-04, Vol.57 (13), p.7085-7100
Main Authors: Athira, K. S., Pandey, P., Prabhakar, K. V. Phani, Chattopadhyay, K., Chatterjee, S.
Format: Article
Language:English
Subjects:
Aging
Alloys
Bead on plate welding
Characterization and Evaluation of Materials
Chemistry and Materials Science
Classical Mechanics
Cobalt base alloys
Composition
Corrosion and anti-corrosives
Corrosion resistance
Corrosion tests
Crystallography and Scattering Methods
Fusion welding
Heat resistant alloys
High temperature
Hot corrosion
Laser beam welding
Lasers
Materials Science
Mechanical properties
Metals & Corrosion
Microstructure
Molybdenum
Oxidation resistance
Polymer Sciences
Powder metallurgy
Precipitates
Solid Mechanics
Solidification
Solids
Superalloys
Titanium
Welded joints
Welding
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Summary:A new class of W-free, precipitation strengthened Co-base superalloys has recently been developed with improved high-temperature strength while maintaining excellent oxidation and hot corrosion resistance. In this study, we report the impact of fusion welding on microstructure and properties of an alloy of this class having a nominal composition Co–30Ni–10Al–5Mo–2Ta–2Ti. We carry out bead-on-plate laser welding of the plates and characterize the microstructure and properties of the welded samples. Fusion zone of the welds consists of FCC γ dendrites and an interdendritic network of ordered γ ′ phase. Finer γ ′ precipitates are observed inside γ dendrites, which form by solid-state transformation during post-solidification cooling. Measurement of phase compositions reveals differences in solid/liquid partitioning behavior of the constituent elements and indicates significant solute trapping for Mo, Ti, and Ta. Experimentally determined partition coefficients for Co and Ni agree reasonably well with thermodynamic predictions obtained using Thermo-Calc, but the prediction for Al contradicts the observations. Although welding-induced microstructural changes lead to a drop in the hardness, it was successfully restored after a post-weld solutionizing-aging treatment. Graphical abstract
ISSN:0022-2461
1573-4803
DOI:10.1007/s10853-022-07117-8