Microstructural evolution of the heat affected zone of a Co–Ti–W alloy upon laser cladding with a CoNiCrAlY coating

• Published in: Materials characterization Vol. 158; p. 109998
• Main Authors: Han, Jaewook, Yoo, Boryung, Im, Hye Ji, Oh, Chang-Seok, Choi, Pyuck-Pa
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.12.2019
• Subjects: Atom probe tomography; Heat affected zone; Laser cladding; Overlay coating; Superalloy; Overlay coating; Superalloy; Heat affected zone; Laser cladding; Atom probe tomography
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2019.109998

We report on the microstructural evolution of the heat affected zone of a γ/γ′-strengthened Co–Ti–W alloy upon laser cladding with a CoNiCrAlY coating. Using electron microscopy and atom probe tomography we observed two distinct heat affect zones, namely γ islands containing γ′ precipitate (∼ 45 nm in size) colonies and heat affected γ/γ′ regions outside the γ islands comprising fine γ′ precipitates (∼ 25 nm in size). Based on the experimental data and thermodynamic calculations, we propose a model for the formation of these two heat affected zones and discuss the differences in the observed precipitate sizes. [Display omitted] •The heat affected zone of a γ/γ′-forming Co–Ti–W alloy upon laser cladding was studied.•γ islands containing γ′ precipitate colonies and heat affected γ/γ′ regions outside the γ islands were observed.•The formation of γ islands containing γ′ precipitate colonies was explained by the melting of the original γ′ precipitates.•Fine γ′ precipitates form by dissolution of the original γ′ precipitates and a subsequent precipitation reaction.